PCI / ACPI: PCI delay optimization from ACPI

An ECN meant to specify possible delay optimizations is available on the PCI website:
https://www.pcisig.com/specifications/conventional/pci_firmware/ECN_fw_latency_optimization_final.pdf
where it has defined two functions for an UUID specified _DSM:
Function 8: If system firmware assumes the responsibility of post Conventional Reset delay (and informs the Operating System via this DSM function) on Sx Resume (such as boot from ACPI S5, or resume from ACPI S4 or S3 states), the Operating System may assume sufficient time has elapsed since the end of reset, and devices within the PCI subsystem are ready for Configuration Access.
If the system firmware supports runtime power gating on any of the device within PCI subsystem covered by this DSM function, the system firmware is responsible for covering the necessary post power-on reset delay.

Function 9: Specify various smaller delay values than required by the SPEC for individual PCI devices like shorter delay values after conventional reset, D3hot to D0 transition, functional level reset, etc.

This patch adds support for function 8 and part of function 9. For function 8, the patch will check if the required _DSM function satisfies the requirement and then set the per PCI device's d3cold_delay variable to zero. For function 9, the values affecting delays after conventional reset and D3hot->D0 are examined and the per PCI device's d3cold_delay and d3_delay are updated if the _DSM's return value is smaller than what the SPEC requires.

Signed-off-by Aaron Lu <[email protected]>

---
 drivers/pci/pci-acpi.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)

drivers/pci/pci-acpi.c +0 -0

index 489063987325..c833b054c00c 100644

drivers/pci/pci-acpi.c +50 -0

+ *   Function 9 of the ACPI _DSM control method, if availabe for a specific PCI
+ *   device, provides various possible delay values that are less than what the
+ *   SPEC requires. Here, we only deal with d3_delay and d3cold_delay. Others
+ *   can be added later.
+ *   Function 8 of the ACPI _DSM control method, if availabe for a specific PCI
+ *   bridge, means all its children devices do not need the reset delay when
+ *   leaving from D3cold state.
+ */
+static void pci_acpi_delay_optimize(struct pci_dev *pdev, struct acpi_device *adev)
+{
+	const u8 uuid[] = {
+		0xd0, 0x37, 0xc9, 0xe5, 0x53, 0x35, 0x7a, 0x4d,
+		0x91, 0x17, 0xea, 0x4d, 0x19, 0xc3, 0x43, 0x4d
+	};
+	int revision = 3, function = 9, value;
+	acpi_handle handle = adev->handle;
+	union acpi_object *obj, *elements;
+
+	obj = acpi_evaluate_dsm(handle, uuid, revision, function, NULL);
+	if (obj) {
+		if (obj->type == ACPI_TYPE_PACKAGE && obj->package.count == 5) {
+			elements = obj->package.elements;
+			if (elements[3].type == ACPI_TYPE_INTEGER) {
+				value = (int)elements[3].integer.value / 1000;
+				if (value < PCI_PM_D3_WAIT)
+					pdev->d3_delay = value;
+			}
+			if (elements[0].type == ACPI_TYPE_INTEGER) {
+				value = (int)elements[0].integer.value / 1000;
+				if (value < PCI_PM_D3COLD_WAIT)
+					pdev->d3cold_delay = value;
+			}
+		}
+		kfree(obj);
+	}
+
+	function = 8;
+	handle = ACPI_HANDLE(pdev->bus->bridge);
+	obj = acpi_evaluate_dsm(handle, uuid, revision, function, NULL);
+	if (!obj)
+		return;
+
+	if (obj->type == ACPI_TYPE_INTEGER && obj->integer.value == 1)
+		pdev->d3cold_delay = 0;
+	kfree(obj);
+}
+
 static void pci_acpi_setup(struct device *dev)
 {
 	struct pci_dev *pci_dev = to_pci_dev(dev);

@@ -566,6 +624,9 @@ static void pci_acpi_setup(struct device *dev)
 	if (!adev)
 		return;
 
+	if (pci_dev->pm_cap)
+		pci_acpi_delay_optimize(pci_dev, adev);
+
 	pci_acpi_add_pm_notifier(adev, pci_dev);
 	if (!adev->wakeup.flags.valid)
 		return;

Quoted 37 lines · Aaron Lu

An ECN meant to specify possible delay optimizations is available on the PCI website:
https://www.pcisig.com/specifications/conventional/pci_firmware/ECN_fw_latency_optimization_final.pdf
where it has defined two functions for an UUID specified _DSM:
Function 8: If system firmware assumes the responsibility of post Conventional Reset delay (and informs the Operating System via this DSM function) on Sx Resume (such as boot from ACPI S5, or resume from ACPI S4 or S3 states), the Operating System may assume sufficient time has elapsed since the end of reset, and devices within the PCI subsystem are ready for Configuration Access.
If the system firmware supports runtime power gating on any of the device within PCI subsystem covered by this DSM function, the system firmware is responsible for covering the necessary post power-on reset delay.

Function 9: Specify various smaller delay values than required by the SPEC for individual PCI devices like shorter delay values after conventional reset, D3hot to D0 transition, functional level reset, etc.

This patch adds support for function 8 and part of function 9. For function 8, the patch will check if the required _DSM function satisfies the requirement and then set the per PCI device's d3cold_delay variable to zero. For function 9, the values affecting delays after conventional reset and D3hot->D0 are examined and the per PCI device's d3cold_delay and d3_delay are updated if the _DSM's return value is smaller than what the SPEC requires.

Signed-off-by Aaron Lu <[email protected]>

---
 drivers/pci/pci-acpi.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)

drivers/pci/pci-acpi.c +0 -0

index 489063987325..c833b054c00c 100644

drivers/pci/pci-acpi.c static struct acpi_device *acpi_pci_find_companion(struct device *dev) · line 566

Quoted 9 lines

drivers/pci/pci-acpi.c +6 -0

@@ -558,6 +558,64 @@ static struct acpi_device *acpi_pci_find_companion(struct device *dev)
 				      check_children);
 }
 
+/**
+ * pci_acpi_delay_optimize - optimize PCI D3 and D3cold delay from ACPI
+ * @pdev: the PCI device whose delay is to be updated
+ * @adev: the companion ACPI device of this PCI device
+ *
+ * Description:

The word "Description" above is not necessary.

drivers/pci/pci-acpi.c static struct acpi_device *acpi_pci_find_companion(struct device *dev) · line 567

Quoted 1 line

drivers/pci/pci-acpi.c +1 -0

+ *   This function is used to update the d3_delay and d3cold_delay of a PCI

I'd simply say

"Update the d3_delay and d3cold_delay of a PCI device from the ACPI _DSM control method of either its own or its parent bridge."

I'd add an empty line here and then the rest of the below starting with "The UUID ...".

drivers/pci/pci-acpi.c static struct acpi_device *acpi_pci_find_companion(struct device *dev) · line 571

Quoted 5 lines

drivers/pci/pci-acpi.c +4 -0

+ *   device from ACPI _DSM control method of either its own or its parent
+ *   bridge device. The UUID of the _DSM control method, together with other
+ *   information like which delay values can be optimized, etc. is defined in
+ *   the fw_latency_optimization ECN availabe on PCIsig.com.

The ECN has a number or title I suppose?

Quoted 62 lines

drivers/pci/pci-acpi.c +50 -0

+ *   Function 9 of the ACPI _DSM control method, if availabe for a specific PCI
+ *   device, provides various possible delay values that are less than what the
+ *   SPEC requires. Here, we only deal with d3_delay and d3cold_delay. Others
+ *   can be added later.
+ *   Function 8 of the ACPI _DSM control method, if availabe for a specific PCI
+ *   bridge, means all its children devices do not need the reset delay when
+ *   leaving from D3cold state.
+ */
+static void pci_acpi_delay_optimize(struct pci_dev *pdev, struct acpi_device *adev)
+{
+	const u8 uuid[] = {
+		0xd0, 0x37, 0xc9, 0xe5, 0x53, 0x35, 0x7a, 0x4d,
+		0x91, 0x17, 0xea, 0x4d, 0x19, 0xc3, 0x43, 0x4d
+	};
+	int revision = 3, function = 9, value;
+	acpi_handle handle = adev->handle;
+	union acpi_object *obj, *elements;
+
+	obj = acpi_evaluate_dsm(handle, uuid, revision, function, NULL);
+	if (obj) {
+		if (obj->type == ACPI_TYPE_PACKAGE && obj->package.count == 5) {
+			elements = obj->package.elements;
+			if (elements[3].type == ACPI_TYPE_INTEGER) {
+				value = (int)elements[3].integer.value / 1000;
+				if (value < PCI_PM_D3_WAIT)
+					pdev->d3_delay = value;
+			}
+			if (elements[0].type == ACPI_TYPE_INTEGER) {
+				value = (int)elements[0].integer.value / 1000;
+				if (value < PCI_PM_D3COLD_WAIT)
+					pdev->d3cold_delay = value;
+			}
+		}
+		kfree(obj);
+	}
+
+	function = 8;
+	handle = ACPI_HANDLE(pdev->bus->bridge);
+	obj = acpi_evaluate_dsm(handle, uuid, revision, function, NULL);
+	if (!obj)
+		return;
+
+	if (obj->type == ACPI_TYPE_INTEGER && obj->integer.value == 1)
+		pdev->d3cold_delay = 0;
+	kfree(obj);
+}
+
 static void pci_acpi_setup(struct device *dev)
 {
 	struct pci_dev *pci_dev = to_pci_dev(dev);

@@ -566,6 +624,9 @@ static void pci_acpi_setup(struct device *dev)
 	if (!adev)
 		return;
 
+	if (pci_dev->pm_cap)
+		pci_acpi_delay_optimize(pci_dev, adev);
+
 	pci_acpi_add_pm_notifier(adev, pci_dev);
 	if (!adev->wakeup.flags.valid)
 		return;

An ECN meant to specify possible delay optimizations is available on the PCI website:
https://www.pcisig.com/specifications/conventional/pci_firmware/ECN_fw_latency_optimization_final.pdf
where it has defined two functions for an UUID specified _DSM:
Function 8: If system firmware assumes the responsibility of post Conventional Reset delay (and informs the Operating System via this DSM function) on Sx Resume (such as boot from ACPI S5, or resume from ACPI S4 or S3 states), the Operating System may assume sufficient time has elapsed since the end of reset, and devices within the PCI subsystem are ready for Configuration Access.
If the system firmware supports runtime power gating on any of the device within PCI subsystem covered by this DSM function, the system firmware is responsible for covering the necessary post power-on reset delay.

Function 9: Specify various smaller delay values than required by the SPEC for individual PCI devices like shorter delay values after conventional reset, D3hot to D0 transition, functional level reset, etc.

This patche adds support for function 8 and part of function 9. For function 8, the patch will check if the required _DSM function satisfies the requirement and then set the per PCI device's d3cold_delay variable to zero. For function 9, the values affecting delays after conventional reset and D3hot->D0 are examined and the per PCI device's d3cold_delay and d3_delay are updated if the _DSM's return value is smaller than what the SPEC requires.

Signed-off-by Aaron Lu <[email protected]>

---
 drivers/pci/pci-acpi.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)

drivers/pci/pci-acpi.c +61 -0

index 489063987325..468c0733838e 100644
@@ -558,6 +558,64 @@ static struct acpi_device *acpi_pci_find_companion(struct device *dev)
 				      check_children);
 }
 
+/**
+ * pci_acpi_delay_optimize - optimize PCI D3 and D3cold delay from ACPI
+ * @pdev: the PCI device whose delay is to be updated
+ * @adev: the companion ACPI device of this PCI device
+ *
+ * Update the d3_delay and d3cold_delay of a PCI device from the ACPI _DSM
+ * control method of either its own or its parent bridge.
+ *
+ * The UUID of the _DSM control method, together with other information like
+ * which delay values can be optimized, etc. is defined in a ECN available on
+ * PCIsig.com titled as: ACPI additions for FW latency optimizations.
+ * Function 9 of the ACPI _DSM control method, if available for a specific PCI
+ * device, provides various possible delay values that are less than what the
+ * SPEC requires. Here, we only deal with d3_delay and d3cold_delay. Others
+ * can be added later.
+ * Function 8 of the ACPI _DSM control method, if available for a specific PCI
+ * bridge, means all its children devices do not need the reset delay when
+ * leaving from D3cold state.
+ */
+static void pci_acpi_delay_optimize(struct pci_dev *pdev, struct acpi_device *adev)
+{
+	const u8 uuid[] = {
+		0xd0, 0x37, 0xc9, 0xe5, 0x53, 0x35, 0x7a, 0x4d,
+		0x91, 0x17, 0xea, 0x4d, 0x19, 0xc3, 0x43, 0x4d
+	};
+	int revision = 3, function = 9, value;
+	acpi_handle handle = adev->handle;
+	union acpi_object *obj, *elements;
+
+	obj = acpi_evaluate_dsm(handle, uuid, revision, function, NULL);
+	if (obj) {
+		if (obj->type == ACPI_TYPE_PACKAGE && obj->package.count == 5) {
+			elements = obj->package.elements;
+			if (elements[3].type == ACPI_TYPE_INTEGER) {
+				value = (int)elements[3].integer.value / 1000;
+				if (value < PCI_PM_D3_WAIT)
+					pdev->d3_delay = value;
+			}
+			if (elements[0].type == ACPI_TYPE_INTEGER) {
+				value = (int)elements[0].integer.value / 1000;
+				if (value < PCI_PM_D3COLD_WAIT)
+					pdev->d3cold_delay = value;
+			}
+		}
+		kfree(obj);
+	}
+
+	function = 8;
+	handle = ACPI_HANDLE(pdev->bus->bridge);
+	obj = acpi_evaluate_dsm(handle, uuid, revision, function, NULL);
+	if (!obj)
+		return;
+
+	if (obj->type == ACPI_TYPE_INTEGER && obj->integer.value == 1)
+		pdev->d3cold_delay = 0;
+	kfree(obj);
+}
+
 static void pci_acpi_setup(struct device *dev)
 {
 	struct pci_dev *pci_dev = to_pci_dev(dev);

@@ -566,6 +624,9 @@ static void pci_acpi_setup(struct device *dev)
 	if (!adev)
 		return;
 
+	if (pci_dev->pm_cap)
+		pci_acpi_delay_optimize(pci_dev, adev);
+
 	pci_acpi_add_pm_notifier(adev, pci_dev);
 	if (!adev->wakeup.flags.valid)
 		return;

I wonder if there is any more comments about this patch?

Quoted 112 lines

An ECN meant to specify possible delay optimizations is available on the PCI website:
https://www.pcisig.com/specifications/conventional/pci_firmware/ECN_fw_latency_optimization_final.pdf
where it has defined two functions for an UUID specified _DSM:
Function 8: If system firmware assumes the responsibility of post Conventional Reset delay (and informs the Operating System via this DSM function) on Sx Resume (such as boot from ACPI S5, or resume from ACPI S4 or S3 states), the Operating System may assume sufficient time has elapsed since the end of reset, and devices within the PCI subsystem are ready for Configuration Access.
If the system firmware supports runtime power gating on any of the device within PCI subsystem covered by this DSM function, the system firmware is responsible for covering the necessary post power-on reset delay.

Function 9: Specify various smaller delay values than required by the SPEC for individual PCI devices like shorter delay values after conventional reset, D3hot to D0 transition, functional level reset, etc.

This patche adds support for function 8 and part of function 9. For function 8, the patch will check if the required _DSM function satisfies the requirement and then set the per PCI device's d3cold_delay variable to zero. For function 9, the values affecting delays after conventional reset and D3hot->D0 are examined and the per PCI device's d3cold_delay and d3_delay are updated if the _DSM's return value is smaller than what the SPEC requires.

Signed-off-by Aaron Lu <[email protected]>

---
 drivers/pci/pci-acpi.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)

drivers/pci/pci-acpi.c +61 -0

index 489063987325..468c0733838e 100644
@@ -558,6 +558,64 @@ static struct acpi_device *acpi_pci_find_companion(struct device *dev)
 				      check_children);
 }
 
+/**
+ * pci_acpi_delay_optimize - optimize PCI D3 and D3cold delay from ACPI
+ * @pdev: the PCI device whose delay is to be updated
+ * @adev: the companion ACPI device of this PCI device
+ *
+ * Update the d3_delay and d3cold_delay of a PCI device from the ACPI _DSM
+ * control method of either its own or its parent bridge.
+ *
+ * The UUID of the _DSM control method, together with other information like
+ * which delay values can be optimized, etc. is defined in a ECN available on
+ * PCIsig.com titled as: ACPI additions for FW latency optimizations.
+ * Function 9 of the ACPI _DSM control method, if available for a specific PCI
+ * device, provides various possible delay values that are less than what the
+ * SPEC requires. Here, we only deal with d3_delay and d3cold_delay. Others
+ * can be added later.
+ * Function 8 of the ACPI _DSM control method, if available for a specific PCI
+ * bridge, means all its children devices do not need the reset delay when
+ * leaving from D3cold state.
+ */
+static void pci_acpi_delay_optimize(struct pci_dev *pdev, struct acpi_device *adev)
+{
+	const u8 uuid[] = {
+		0xd0, 0x37, 0xc9, 0xe5, 0x53, 0x35, 0x7a, 0x4d,
+		0x91, 0x17, 0xea, 0x4d, 0x19, 0xc3, 0x43, 0x4d
+	};
+	int revision = 3, function = 9, value;
+	acpi_handle handle = adev->handle;
+	union acpi_object *obj, *elements;
+
+	obj = acpi_evaluate_dsm(handle, uuid, revision, function, NULL);
+	if (obj) {
+		if (obj->type == ACPI_TYPE_PACKAGE && obj->package.count == 5) {
+			elements = obj->package.elements;
+			if (elements[3].type == ACPI_TYPE_INTEGER) {
+				value = (int)elements[3].integer.value / 1000;
+				if (value < PCI_PM_D3_WAIT)
+					pdev->d3_delay = value;
+			}
+			if (elements[0].type == ACPI_TYPE_INTEGER) {
+				value = (int)elements[0].integer.value / 1000;
+				if (value < PCI_PM_D3COLD_WAIT)
+					pdev->d3cold_delay = value;
+			}
+		}
+		kfree(obj);
+	}
+
+	function = 8;
+	handle = ACPI_HANDLE(pdev->bus->bridge);
+	obj = acpi_evaluate_dsm(handle, uuid, revision, function, NULL);
+	if (!obj)
+		return;
+
+	if (obj->type == ACPI_TYPE_INTEGER && obj->integer.value == 1)
+		pdev->d3cold_delay = 0;
+	kfree(obj);
+}
+
 static void pci_acpi_setup(struct device *dev)
 {
 	struct pci_dev *pci_dev = to_pci_dev(dev);

@@ -566,6 +624,9 @@ static void pci_acpi_setup(struct device *dev)
 	if (!adev)
 		return;
 
+	if (pci_dev->pm_cap)
+		pci_acpi_delay_optimize(pci_dev, adev);
+
 	pci_acpi_add_pm_notifier(adev, pci_dev);
 	if (!adev->wakeup.flags.valid)
 		return;

An ECN meant to specify possible delay optimizations is available on the PCI website:
https://www.pcisig.com/specifications/conventional/pci_firmware/ECN_fw_latency_optimization_final.pdf
where it has defined two functions for an UUID specified _DSM:
Function 8: If system firmware assumes the responsibility of post Conventional Reset delay (and informs the Operating System via this DSM function) on Sx Resume (such as boot from ACPI S5, or resume from ACPI S4 or S3 states), the Operating System may assume sufficient time has elapsed since the end of reset, and devices within the PCI subsystem are ready for Configuration Access.
If the system firmware supports runtime power gating on any of the device within PCI subsystem covered by this DSM function, the system firmware is responsible for covering the necessary post power-on reset delay.

Function 9: Specify various smaller delay values than required by the SPEC for individual PCI devices like shorter delay values after conventional reset, D3hot to D0 transition, functional level reset, etc.

This patche adds support for function 8 and part of function 9. For function 8, the patch will check if the required _DSM function satisfies the requirement and then set the per PCI device's d3cold_delay variable to zero. For function 9, the values affecting delays after conventional reset and D3hot->D0 are examined and the per PCI device's d3cold_delay and d3_delay are updated if the _DSM's return value is smaller than what the SPEC requires.

Signed-off-by Aaron Lu <[email protected]>

---
 drivers/pci/pci-acpi.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)

drivers/pci/pci-acpi.c +15 -0

index 489063987325..468c0733838e 100644
@@ -558,6 +558,64 @@ static struct acpi_device *acpi_pci_find_companion(struct device *dev)
 				      check_children);
 }
 
+/**
+ * pci_acpi_delay_optimize - optimize PCI D3 and D3cold delay from ACPI
+ * @pdev: the PCI device whose delay is to be updated
+ * @adev: the companion ACPI device of this PCI device
+ *
+ * Update the d3_delay and d3cold_delay of a PCI device from the ACPI _DSM
+ * control method of either its own or its parent bridge.
+ *
+ * The UUID of the _DSM control method, together with other information like
+ * which delay values can be optimized, etc. is defined in a ECN available on
+ * PCIsig.com titled as: ACPI additions for FW latency optimizations.
+ * Function 9 of the ACPI _DSM control method, if available for a specific PCI
+ * device, provides various possible delay values that are less than what the
+ * SPEC requires. Here, we only deal with d3_delay and d3cold_delay. Others
+ * can be added later.

drivers/pci/pci-acpi.c +8 -0

+	int revision = 3, function = 9, value;
+	acpi_handle handle = adev->handle;
+	union acpi_object *obj, *elements;
+
+	obj = acpi_evaluate_dsm(handle, uuid, revision, function, NULL);
+	if (obj) {
+		if (obj->type == ACPI_TYPE_PACKAGE && obj->package.count == 5) {
+			elements = obj->package.elements;

drivers/pci/pci-acpi.c +11 -0

+	if (!obj)
+		return;
+
+	if (obj->type == ACPI_TYPE_INTEGER && obj->integer.value == 1)
+		pdev->d3cold_delay = 0;
+	kfree(obj);
+}
+
 static void pci_acpi_setup(struct device *dev)
 {
 	struct pci_dev *pci_dev = to_pci_dev(dev);

@@ -566,6 +624,9 @@ static void pci_acpi_setup(struct device *dev)
 	if (!adev)
 		return;
 
+	if (pci_dev->pm_cap)
+		pci_acpi_delay_optimize(pci_dev, adev);
+
 	pci_acpi_add_pm_notifier(adev, pci_dev);
 	if (!adev->wakeup.flags.valid)
 		return;

Signature · 1 line

2.1.0

Quoted 55 lines · Aaron Lu

An ECN meant to specify possible delay optimizations is available on the PCI website:
https://www.pcisig.com/specifications/conventional/pci_firmware/ECN_fw_latency_optimization_final.pdf
where it has defined two functions for an UUID specified _DSM:
Function 8: If system firmware assumes the responsibility of post Conventional Reset delay (and informs the Operating System via this DSM function) on Sx Resume (such as boot from ACPI S5, or resume from ACPI S4 or S3 states), the Operating System may assume sufficient time has elapsed since the end of reset, and devices within the PCI subsystem are ready for Configuration Access.
If the system firmware supports runtime power gating on any of the device within PCI subsystem covered by this DSM function, the system firmware is responsible for covering the necessary post power-on reset delay.

Function 9: Specify various smaller delay values than required by the SPEC for individual PCI devices like shorter delay values after conventional reset, D3hot to D0 transition, functional level reset, etc.

This patche adds support for function 8 and part of function 9. For function 8, the patch will check if the required _DSM function satisfies the requirement and then set the per PCI device's d3cold_delay variable to zero. For function 9, the values affecting delays after conventional reset and D3hot->D0 are examined and the per PCI device's d3cold_delay and d3_delay are updated if the _DSM's return value is smaller than what the SPEC requires.

Signed-off-by Aaron Lu <[email protected]>

---
 drivers/pci/pci-acpi.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)

drivers/pci/pci-acpi.c +15 -0

index 489063987325..468c0733838e 100644
@@ -558,6 +558,64 @@ static struct acpi_device *acpi_pci_find_companion(struct device *dev)
 				      check_children);
 }
 
+/**
+ * pci_acpi_delay_optimize - optimize PCI D3 and D3cold delay from ACPI
+ * @pdev: the PCI device whose delay is to be updated
+ * @adev: the companion ACPI device of this PCI device
+ *
+ * Update the d3_delay and d3cold_delay of a PCI device from the ACPI _DSM
+ * control method of either its own or its parent bridge.
+ *
+ * The UUID of the _DSM control method, together with other information like
+ * which delay values can be optimized, etc. is defined in a ECN available on
+ * PCIsig.com titled as: ACPI additions for FW latency optimizations.
+ * Function 9 of the ACPI _DSM control method, if available for a specific PCI
+ * device, provides various possible delay values that are less than what the
+ * SPEC requires. Here, we only deal with d3_delay and d3cold_delay. Others
+ * can be added later.

drivers/pci/pci-acpi.c static struct acpi_device *acpi_pci_find_companion(struct device *dev) · line 585

Quoted 10 lines

drivers/pci/pci-acpi.c +10 -0

+ * Function 8 of the ACPI _DSM control method, if available for a specific PCI
+ * bridge, means all its children devices do not need the reset delay when
+ * leaving from D3cold state.
+ */
+static void pci_acpi_delay_optimize(struct pci_dev *pdev, struct acpi_device *adev)
+{
+	const u8 uuid[] = {
+		0xd0, 0x37, 0xc9, 0xe5, 0x53, 0x35, 0x7a, 0x4d,
+		0x91, 0x17, 0xea, 0x4d, 0x19, 0xc3, 0x43, 0x4d
+	};

This is a duplicate of device_label_dsm_uuid[] from drivers/pci/pci-label.c. I don't really want two copies.

That UUID is not specific to device labels, so device_label_dsm_uuid[] is mis-named anyway. It's just the UUID for the single _DSM for PCI (see PCI Firmware Specification, r3.0, sec 4.6), and all these different things (device label, reset delay, slot info, etc.) use the same UUID with different function indices.

We should also make #defines for the function indices instead of using hard-coded numbers here.

Quoted 14 lines

drivers/pci/pci-acpi.c +13 -0

+	int revision = 3, function = 9, value;
+	acpi_handle handle = adev->handle;
+	union acpi_object *obj, *elements;
+
+	obj = acpi_evaluate_dsm(handle, uuid, revision, function, NULL);
+	if (obj) {
+		if (obj->type == ACPI_TYPE_PACKAGE && obj->package.count == 5) {
+			elements = obj->package.elements;
+			if (elements[3].type == ACPI_TYPE_INTEGER) {
+				value = (int)elements[3].integer.value / 1000;
+				if (value < PCI_PM_D3_WAIT)
+					pdev->d3_delay = value;
+			}

drivers/pci/pci-acpi.c static struct acpi_device *acpi_pci_find_companion(struct device *dev) · line 603

Quoted 5 lines

drivers/pci/pci-acpi.c +5 -0

+			if (elements[0].type == ACPI_TYPE_INTEGER) {
+				value = (int)elements[0].integer.value / 1000;
+				if (value < PCI_PM_D3COLD_WAIT)
+					pdev->d3cold_delay = value;
+			}

Unless there's a reason to do this in "element[3], element[0]" order, please do it in the natural "0, 3" order.

drivers/pci/pci-acpi.c static struct acpi_device *acpi_pci_find_companion(struct device *dev) · line 610

Quoted 8 lines

drivers/pci/pci-acpi.c +7 -0

+		}
+		kfree(obj);
+	}
+
+	function = 8;
+	handle = ACPI_HANDLE(pdev->bus->bridge);
+	obj = acpi_evaluate_dsm(handle, uuid, revision, function, NULL);

Hmm. I think the ECN is poorly worded here. Sec 4.6.8 says "This object [_DSM] can only be placed within the scope of a PCI host bus." I think it means "this _DSM *function* can only be implemented ..." (since any device can have a _DSM), and I think it means "host *bridge*" (not bus, since I don't think there's an ACPI object for a PCI bus).

It probably should say "This function can be implemented only by a _DSM method within the scope of a PCI host bridge."

Anyway, I think this patch looks for a _DSM in PCI-PCI bridge devices as well as PCI host bridge devices, and the ECN says any values returned by function 8 of a non-host bridge _DSM method should be ignored. At least, that's how I read it.

I think you need something in pci_root.c that evaluates _DSM function 8 for the host bridge, and then some mechanism for all the devices under that bridge to inherit the result.

Quoted 25 lines

drivers/pci/pci-acpi.c +11 -0

+	if (!obj)
+		return;
+
+	if (obj->type == ACPI_TYPE_INTEGER && obj->integer.value == 1)
+		pdev->d3cold_delay = 0;
+	kfree(obj);
+}
+
 static void pci_acpi_setup(struct device *dev)
 {
 	struct pci_dev *pci_dev = to_pci_dev(dev);

@@ -566,6 +624,9 @@ static void pci_acpi_setup(struct device *dev)
 	if (!adev)
 		return;
 
+	if (pci_dev->pm_cap)
+		pci_acpi_delay_optimize(pci_dev, adev);
+
 	pci_acpi_add_pm_notifier(adev, pci_dev);
 	if (!adev->wakeup.flags.valid)
 		return;

Signature · 1 line

2.1.0

Quoted 3 lines · Bjorn Helgaas

I think you need something in pci_root.c that evaluates _DSM function 8 for the host bridge, and then some mechanism for all the devices under that bridge to inherit the result.

Thanks for the suggestion, will try to do this in the next revision.

An ECN meant to specify possible delay optimizations is available on the PCI website:
https://www.pcisig.com/specifications/conventional/pci_firmware/ECN_fw_latency_optimization_final.pdf
where it has defined two functions for an UUID specified _DSM:
Function 8: If system firmware assumes the responsibility of post Conventional Reset delay (and informs the Operating System via this DSM function) on Sx Resume (such as boot from ACPI S5, or resume from ACPI S4 or S3 states), the Operating System may assume sufficient time has elapsed since the end of reset, and devices within the PCI subsystem are ready for Configuration Access.
If the system firmware supports runtime power gating on any of the device within PCI subsystem covered by this DSM function, the system firmware is responsible for covering the necessary post power-on reset delay.

Function 9: Specify various smaller delay values than required by the SPEC for individual PCI devices like shorter delay values after conventional reset, D3hot to D0 transition, functional level reset, etc.

This patche adds support for function 8 and part of function 9. For function 8, the patch will check if the required _DSM function satisfies the requirement and then set the per PCI device's d3cold_delay variable to zero. For function 9, the values affecting delays after conventional reset and D3hot->D0 are examined and the per PCI device's d3cold_delay and d3_delay are updated if the _DSM's return value is smaller than what the SPEC requires.

Signed-off-by Aaron Lu <[email protected]>

---
 drivers/pci/pci-acpi.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++
 drivers/pci/pci.h      |  2 ++
 2 files changed, 65 insertions(+)

drivers/pci/pci-acpi.c +42 -0

index 6ef2019073e2..2ebd02d814d7 100644
@@ -563,6 +563,66 @@ static struct acpi_device *acpi_pci_find_companion(struct device *dev)
 				      check_children);
 }
 
+/**
+ * pci_acpi_delay_optimize - optimize PCI D3 and D3cold delay from ACPI
+ * @pdev: the PCI device whose delay is to be updated
+ * @adev: the companion ACPI device of this PCI device
+ *
+ * Update the d3_delay and d3cold_delay of a PCI device from the ACPI _DSM
+ * control method of either its own or its parent bridge.
+ *
+ * The UUID of the _DSM control method, together with other information like
+ * which delay values can be optimized, etc. is defined in a ECN available on
+ * PCIsig.com titled as: ACPI additions for FW latency optimizations.
+ * Function 9 of the ACPI _DSM control method, if available for a specific PCI
+ * device, provides various possible delay values that are less than what the
+ * SPEC requires. Here, we only deal with d3_delay and d3cold_delay. Others
+ * can be added later.
+ * Function 8 of the ACPI _DSM control method, if available for the PCI host
+ * bridge, means all its children devices do not need the reset delay when
+ * leaving from D3cold state.
+ */
+static void pci_acpi_delay_optimize(struct pci_dev *pdev,
+				    struct acpi_device *adev)
+{
+	acpi_handle handle = adev->handle;
+	int value;
+	union acpi_object *obj, *elements;
+
+	obj = acpi_evaluate_dsm(handle, pci_acpi_dsm_uuid, 3,
+				FUNCTION_DELAY_DSM, NULL);
+	if (obj) {
+		if (obj->type == ACPI_TYPE_PACKAGE && obj->package.count == 5) {
+			elements = obj->package.elements;
+			if (elements[0].type == ACPI_TYPE_INTEGER) {
+				value = (int)elements[0].integer.value / 1000;
+				if (value < PCI_PM_D3COLD_WAIT)
+					pdev->d3cold_delay = value;
+			}
+			if (elements[3].type == ACPI_TYPE_INTEGER) {
+				value = (int)elements[3].integer.value / 1000;
+				if (value < PCI_PM_D3_WAIT)
+					pdev->d3_delay = value;
+			}
+		}

drivers/pci/pci-acpi.c +11 -0

+	if (!obj)
+		return;
+
+	if (obj->type == ACPI_TYPE_INTEGER && obj->integer.value == 1)
+		pdev->d3cold_delay = 0;
+	kfree(obj);
+}
+
 static void pci_acpi_setup(struct device *dev)
 {
 	struct pci_dev *pci_dev = to_pci_dev(dev);

@@ -571,6 +631,9 @@ static void pci_acpi_setup(struct device *dev)
 	if (!adev)
 		return;
 
+	if (pci_dev->pm_cap)
+		pci_acpi_delay_optimize(pci_dev, adev);
+
 	pci_acpi_add_pm_notifier(adev, pci_dev);
 	if (!adev->wakeup.flags.valid)
 		return;

drivers/pci/pci.h +2 -0

index c901ab84cf3b..3eaefac5acc5 100644
@@ -325,6 +325,8 @@ static inline int pci_dev_specific_reset(struct pci_dev *dev, int probe)
 extern const u8 pci_acpi_dsm_uuid[];
 
 #define DEVICE_LABEL_DSM	0x07
+#define RESET_DELAY_DSM		0x08
+#define FUNCTION_DELAY_DSM	0x09
 #endif
 
 #endif /* DRIVERS_PCI_H */

Signature · 1 line

2.1.0

According to the PCI firmware spec, there is only one assigned UUID used for PCI system so rename the device_label_dsm_uuid to something more common as: pci_acpi_dsm_uuid and put it in drivers/pci/pci-acpi.c. Make that uuid array extern in the pci.h so that other code can also make use of it.

This patch shouldn't bring any functional change.

Signed-off-by Aaron Lu <[email protected]>

---
 drivers/pci/pci-acpi.c  |  5 +++++
 drivers/pci/pci-label.c | 11 ++---------
 drivers/pci/pci.h       |  6 ++++++
 3 files changed, 13 insertions(+), 9 deletions(-)

drivers/pci/pci-acpi.c +0 -0

index 489063987325..6ef2019073e2 100644

drivers/pci/pci-acpi.c +5 -0

+const u8 pci_acpi_dsm_uuid[] = {
+	0xd0, 0x37, 0xc9, 0xe5, 0x53, 0x35, 0x7a, 0x4d,
+	0x91, 0x17, 0xea, 0x4d, 0x19, 0xc3, 0x43, 0x4d
+};
+
 phys_addr_t acpi_pci_root_get_mcfg_addr(acpi_handle handle)
 {
 	acpi_status status = AE_NOT_EXIST;

drivers/pci/pci-label.c +2 -9

index 2ab1b47c7651..024b5c179348 100644
@@ -31,8 +31,6 @@
 #include <linux/pci-acpi.h>
 #include "pci.h"
 
-#define	DEVICE_LABEL_DSM	0x07
-
 #ifdef CONFIG_DMI
 enum smbios_attr_enum {
 	SMBIOS_ATTR_NONE = 0,

@@ -148,11 +146,6 @@ static inline void pci_remove_smbiosname_file(struct pci_dev *pdev)
 #endif
 
 #ifdef CONFIG_ACPI
-static const char device_label_dsm_uuid[] = {
-	0xD0, 0x37, 0xC9, 0xE5, 0x53, 0x35, 0x7A, 0x4D,
-	0x91, 0x17, 0xEA, 0x4D, 0x19, 0xC3, 0x43, 0x4D
-};
-
 enum acpi_attr_enum {
 	ACPI_ATTR_LABEL_SHOW,
 	ACPI_ATTR_INDEX_SHOW,

@@ -179,7 +172,7 @@ static int dsm_get_label(struct device *dev, char *buf,
 	if (!handle)
 		return -1;
 
-	obj = acpi_evaluate_dsm(handle, device_label_dsm_uuid, 0x2,
+	obj = acpi_evaluate_dsm(handle, pci_acpi_dsm_uuid, 0x2,
 				DEVICE_LABEL_DSM, NULL);
 	if (!obj)
 		return -1;

@@ -219,7 +212,7 @@ static bool device_has_dsm(struct device *dev)
 	if (!handle)
 		return false;
 
-	return !!acpi_check_dsm(handle, device_label_dsm_uuid, 0x2,
+	return !!acpi_check_dsm(handle, pci_acpi_dsm_uuid, 0x2,
 				1 << DEVICE_LABEL_DSM);
 }
 

drivers/pci/pci.h +0 -0

index 4091f82239cd..c901ab84cf3b 100644

drivers/pci/pci.h +1 -0

+
 #endif /* DRIVERS_PCI_H */

So _DSM is an ACPI-defined object and please spell its name like that. Also please spell UUID in capitals if that's not a problem.

Quoted 15 lines

According to the PCI firmware spec, there is only one assigned UUID used for PCI system so rename the device_label_dsm_uuid to something more common as: pci_acpi_dsm_uuid and put it in drivers/pci/pci-acpi.c. Make that uuid array extern in the pci.h so that other code can also make use of it.

This patch shouldn't bring any functional change.

Signed-off-by Aaron Lu <[email protected]>

---
 drivers/pci/pci-acpi.c  |  5 +++++
 drivers/pci/pci-label.c | 11 ++---------
 drivers/pci/pci.h       |  6 ++++++
 3 files changed, 13 insertions(+), 9 deletions(-)

drivers/pci/pci-acpi.c line 20

Quoted 8 lines

drivers/pci/pci-acpi.c +0 -0

index 489063987325..6ef2019073e2 100644
@@ -18,6 +18,11 @@
 #include <linux/pm_qos.h>
 #include "pci.h"
 

Please add a comment referring to the document defining the UUID here.

Quoted 60 lines

drivers/pci/pci-acpi.c +5 -0

+const u8 pci_acpi_dsm_uuid[] = {
+	0xd0, 0x37, 0xc9, 0xe5, 0x53, 0x35, 0x7a, 0x4d,
+	0x91, 0x17, 0xea, 0x4d, 0x19, 0xc3, 0x43, 0x4d
+};
+
 phys_addr_t acpi_pci_root_get_mcfg_addr(acpi_handle handle)
 {
 	acpi_status status = AE_NOT_EXIST;

drivers/pci/pci-label.c +2 -9

index 2ab1b47c7651..024b5c179348 100644
@@ -31,8 +31,6 @@
 #include <linux/pci-acpi.h>
 #include "pci.h"
 
-#define	DEVICE_LABEL_DSM	0x07
-
 #ifdef CONFIG_DMI
 enum smbios_attr_enum {
 	SMBIOS_ATTR_NONE = 0,

@@ -148,11 +146,6 @@ static inline void pci_remove_smbiosname_file(struct pci_dev *pdev)
 #endif
 
 #ifdef CONFIG_ACPI
-static const char device_label_dsm_uuid[] = {
-	0xD0, 0x37, 0xC9, 0xE5, 0x53, 0x35, 0x7A, 0x4D,
-	0x91, 0x17, 0xEA, 0x4D, 0x19, 0xC3, 0x43, 0x4D
-};
-
 enum acpi_attr_enum {
 	ACPI_ATTR_LABEL_SHOW,
 	ACPI_ATTR_INDEX_SHOW,

@@ -179,7 +172,7 @@ static int dsm_get_label(struct device *dev, char *buf,
 	if (!handle)
 		return -1;
 
-	obj = acpi_evaluate_dsm(handle, device_label_dsm_uuid, 0x2,
+	obj = acpi_evaluate_dsm(handle, pci_acpi_dsm_uuid, 0x2,
 				DEVICE_LABEL_DSM, NULL);
 	if (!obj)
 		return -1;

@@ -219,7 +212,7 @@ static bool device_has_dsm(struct device *dev)
 	if (!handle)
 		return false;
 
-	return !!acpi_check_dsm(handle, device_label_dsm_uuid, 0x2,
+	return !!acpi_check_dsm(handle, pci_acpi_dsm_uuid, 0x2,
 				1 << DEVICE_LABEL_DSM);
 }
 

drivers/pci/pci.h +0 -0

index 4091f82239cd..c901ab84cf3b 100644
@@ -321,4 +321,10 @@ static inline int pci_dev_specific_reset(struct pci_dev *dev, int probe)
 }
 #endif
 

drivers/pci/pci.h static inline int pci_dev_specific_reset(struct pci_dev *dev, int probe) · line 328

Quoted 5 lines

drivers/pci/pci.h +5 -0

+#ifdef CONFIG_ACPI
+extern const u8 pci_acpi_dsm_uuid[];
+
+#define DEVICE_LABEL_DSM	0x07
+#endif

We have pci-acpi.h. Maybe define this stuff in there and make the user(s) include that?

Quoted 4 lines

drivers/pci/pci.h +1 -0

+
 #endif /* DRIVERS_PCI_H */

Quoted 2 lines · Rafael J. Wysocki

So _DSM is an ACPI-defined object and please spell its name like that. Also please spell UUID in capitals if that's not a problem.

Something like acpi_pci_dsm_UUID?

The ECN says this function is in a host bridge scope and applies to the PCI subsystem beneath the bridge. This code does not map well to that because:

1) It evaluates _DSM more times than necessary (we only need to do it once per host bridge, and this does it once for every PCI device immediately below a host brige).

2) The settings are only applied to immediate children of the host bridge, not to devices deeper in the hierarchy.

3) A reader of the ECN will expect the corresponding code to be in the host bridge driver (pci_root.c) where we deal with other host bridge properties, not in per-PCI device code like this.

4) The ECN is not explicit about this, but if both function 8 (which applies to a whole hierarchy) and function 9 (which applies to a single PCI device) are implemented for the same PCI device, I would expect function 9 to take precedence over function 8. This patch does the reverse, since function 8 will overwrite any d3cold_delay that was set above by function 9.

From 05b625d2444d90e37392dd835a97c0b582fd221f Mon Sep 17 00:00:00 2001

Quoted 15 lines · Bjorn Helgaas

The ECN says this function is in a host bridge scope and applies to the PCI subsystem beneath the bridge. This code does not map well to that because:

1) It evaluates _DSM more times than necessary (we only need to do it once per host bridge, and this does it once for every PCI device immediately below a host brige).

2) The settings are only applied to immediate children of the host bridge, not to devices deeper in the hierarchy.

3) A reader of the ECN will expect the corresponding code to be in the host bridge driver (pci_root.c) where we deal with other host bridge properties, not in per-PCI device code like this.

Quoted 6 lines

4) The ECN is not explicit about this, but if both function 8 (which applies to a whole hierarchy) and function 9 (which applies to a single PCI device) are implemented for the same PCI device, I would expect function 9 to take precedence over function 8. This patch does the reverse, since function 8 will overwrite any d3cold_delay that was set above by function 9.

I tried to do this in drivers/acpi/pci_root.c, but didn't find a proper way to pass this information down during PCI device scan time. So instead, I did it in the pci root bus add time: acpi_pci_add_bus, which is used by both the x86 code and ia64 code. Suggestions are welcome and appreciated.

From 05b625d2444d90e37392dd835a97c0b582fd221f Mon Sep 17 00:00:00 2001
From: Aaron Lu <[email protected]>
Date: Fri, 14 Nov 2014 16:56:43 +0800
Subject: [PATCH v2 2/2] PCI / ACPI: PCI delay optimization from ACPI

An ECN meant to specify possible delay optimizations is available on the PCI website:
https://www.pcisig.com/specifications/conventional/pci_firmware/ECN_fw_latency_optimization_final.pdf
where it has defined two functions for an UUID specified _DSM:
Function 8: If system firmware assumes the responsibility of post Conventional Reset delay (and informs the Operating System via this DSM function) on Sx Resume (such as boot from ACPI S5, or resume from ACPI S4 or S3 states), the Operating System may assume sufficient time has elapsed since the end of reset, and devices within the PCI subsystem are ready for Configuration Access.
If the system firmware supports runtime power gating on any of the device within PCI subsystem covered by this DSM function, the system firmware is responsible for covering the necessary post power-on reset delay.

Function 9: Specify various smaller delay values than required by the SPEC for individual PCI devices like shorter delay values after conventional reset, D3hot to D0 transition, functional level reset, etc.

This patche adds support for function 8 and part of function 9. For function 8, the patch will check if the required _DSM function satisfies the requirement and then all the host bus' immediate children PCI device's d3cold_delay variable will be updated to zero. For function 9, the values affecting delays after conventional reset and D3hot->D0 are examined and the per PCI device's d3cold_delay and d3_delay are updated if the _DSM's return value is smaller than what the SPEC requires. Function 9's value takes precedence over function 8.

Signed-off-by Aaron Lu <[email protected]>

---
 drivers/pci/pci-acpi.c   | 65 ++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/pci-acpi.h |  2 ++
 include/linux/pci.h      |  1 +
 3 files changed, 68 insertions(+)

drivers/pci/pci-acpi.c +2 -0

index e0afc94aca01..220371c2def4 100644
@@ -537,11 +537,24 @@ static struct pci_platform_pm_ops acpi_pci_platform_pm = {
 
 void acpi_pci_add_bus(struct pci_bus *bus)
 {
+	union acpi_object *obj;
+
 	if (acpi_pci_disabled || !bus->bridge)
 		return;

drivers/pci/pci-acpi.c +17 -0

 }
 
 void acpi_pci_remove_bus(struct pci_bus *bus)

@@ -567,6 +580,55 @@ static struct acpi_device *acpi_pci_find_companion(struct device *dev)
 				      check_children);
 }
 
+/**
+ * pci_acpi_delay_optimize - optimize PCI D3 and D3cold delay from ACPI
+ * @pdev: the PCI device whose delay is to be updated
+ * @adev: the companion ACPI device of this PCI device
+ *
+ * Update the d3_delay and d3cold_delay of a PCI device from the ACPI _DSM
+ * control method of either its own or its parent bridge.
+ *
+ * The UUID of the _DSM control method, together with other information like
+ * which delay values can be optimized, etc. is defined in a ECN available on
+ * PCIsig.com titled as: ACPI additions for FW latency optimizations.
+ * Function 9 of the ACPI _DSM control method, if available for a specific PCI
+ * device, provides various possible delay values that are less than what the
+ * SPEC requires. Here, we only deal with d3_delay and d3cold_delay. Others
+ * can be added later.
+ * Function 8 of the ACPI _DSM control method, if available for the PCI host
+ * bridge(reflected by the bus' ignore_reset_delay filed), means all its

drivers/pci/pci-acpi.c +22 -0

+
+	obj = acpi_evaluate_dsm(handle, pci_acpi_dsm_uuid, 3,
+				FUNCTION_DELAY_DSM, NULL);
+	if (!obj)
+		return;
+
+	if (obj->type == ACPI_TYPE_PACKAGE && obj->package.count == 5) {
+		elements = obj->package.elements;
+		if (elements[0].type == ACPI_TYPE_INTEGER) {
+			value = (int)elements[0].integer.value / 1000;
+			if (value < PCI_PM_D3COLD_WAIT)
+				pdev->d3cold_delay = value;
+		}
+		if (elements[3].type == ACPI_TYPE_INTEGER) {
+			value = (int)elements[3].integer.value / 1000;
+			if (value < PCI_PM_D3_WAIT)
+				pdev->d3_delay = value;
+		}
+	}
+	kfree(obj);
+}
+
 static void pci_acpi_setup(struct device *dev)
 {
 	struct pci_dev *pci_dev = to_pci_dev(dev);

drivers/pci/pci-acpi.c +1 -0

+
 	pci_acpi_add_pm_notifier(adev, pci_dev);
 	if (!adev->wakeup.flags.valid)
 		return;

include/linux/pci-acpi.h +2 -0

index 3801c704a945..a965efa52152 100644
@@ -79,6 +79,8 @@ static inline void acpiphp_check_host_bridge(struct acpi_device *adev) { }
 
 extern const u8 pci_acpi_dsm_uuid[];
 #define DEVICE_LABEL_DSM	0x07
+#define RESET_DELAY_DSM		0x08
+#define FUNCTION_DELAY_DSM	0x09
 
 #else	/* CONFIG_ACPI */
 static inline void acpi_pci_add_bus(struct pci_bus *bus) { }

include/linux/pci.h +1 -0

index a379513bddef..1e56c464d058 100644
@@ -471,6 +471,7 @@ struct pci_bus {
 	struct bin_attribute	*legacy_io; /* legacy I/O for this bus */
 	struct bin_attribute	*legacy_mem; /* legacy mem */
 	unsigned int		is_added:1;
+	unsigned int		ignore_reset_delay:1;
 };
 
 #define to_pci_bus(n)	container_of(n, struct pci_bus, dev)

Signature · 6 lines

2.1.0

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Quoted 13 lines · Aaron Lu

drivers/pci/pci-acpi.c +2 -0

index e0afc94aca01..220371c2def4 100644
@@ -537,11 +537,24 @@ static struct pci_platform_pm_ops acpi_pci_platform_pm = {
 
 void acpi_pci_add_bus(struct pci_bus *bus)
 {
+	union acpi_object *obj;
+
 	if (acpi_pci_disabled || !bus->bridge)
 		return;
 

drivers/pci/pci-acpi.c static struct pci_platform_pm_ops acpi_pci_platform_pm = { · line 553

Quoted 9 lines

drivers/pci/pci-acpi.c +7 -0

 	acpi_pci_slot_enumerate(bus);
 	acpiphp_enumerate_slots(bus);
+
+	/*
+	 * For a host bridge, check its _DSM for function 8 and if
+	 * that is available, mark it in the corresponding pci_bus.
+	 */
+	if (bus->bridge->parent)
+		return;

This is not really an obvious way of testing for a host bridge. I think pci_is_root_bus() would be a better way, but I'm still hoping for something in pci_root.c instead. There is find_pci_host_bridge(), which might be useful (it's currently static but we might want to rename and export it for this and other reasons).

drivers/pci/pci-acpi.c static struct pci_platform_pm_ops acpi_pci_platform_pm = { · line 557

Quoted 5 lines

drivers/pci/pci-acpi.c +4 -0

+	obj = acpi_evaluate_dsm(ACPI_HANDLE(bus->bridge), pci_acpi_dsm_uuid, 3,
+				RESET_DELAY_DSM, NULL);
+	if (obj && obj->type == ACPI_TYPE_INTEGER && obj->integer.value == 1)
+		bus->ignore_reset_delay = 1;

I think you need to free "obj" here. Other acpi_evaluate_dsm() callers use ACPI_FREE().

Quoted 32 lines

drivers/pci/pci-acpi.c +24 -0

 }
 
 void acpi_pci_remove_bus(struct pci_bus *bus)

@@ -567,6 +580,55 @@ static struct acpi_device *acpi_pci_find_companion(struct device *dev)
 				      check_children);
 }
 
+/**
+ * pci_acpi_delay_optimize - optimize PCI D3 and D3cold delay from ACPI
+ * @pdev: the PCI device whose delay is to be updated
+ * @adev: the companion ACPI device of this PCI device
+ *
+ * Update the d3_delay and d3cold_delay of a PCI device from the ACPI _DSM
+ * control method of either its own or its parent bridge.
+ *
+ * The UUID of the _DSM control method, together with other information like
+ * which delay values can be optimized, etc. is defined in a ECN available on
+ * PCIsig.com titled as: ACPI additions for FW latency optimizations.
+ * Function 9 of the ACPI _DSM control method, if available for a specific PCI
+ * device, provides various possible delay values that are less than what the
+ * SPEC requires. Here, we only deal with d3_delay and d3cold_delay. Others
+ * can be added later.
+ * Function 8 of the ACPI _DSM control method, if available for the PCI host
+ * bridge(reflected by the bus' ignore_reset_delay filed), means all its
+ * children devices do not need the reset delay when leaving from D3cold state.
+ */
+static void pci_acpi_delay_optimize(struct pci_dev *pdev,
+				    acpi_handle handle)
+{
+	int value;
+	union acpi_object *obj, *elements;

drivers/pci/pci-acpi.c static struct acpi_device *acpi_pci_find_companion(struct device *dev) · line 609

Quoted 3 lines

drivers/pci/pci-acpi.c +3 -0

+
+	if (pdev->bus->ignore_reset_delay)
+		pdev->d3cold_delay = 0;

I think this only propagates the function 8 result to the immediate children of the host bridge, i.e., devices on the root bus. But the ECN says it affects the entire hierarchy. Can you put the ignore_reset_delay bit in the struct pci_host_bridge instead?

Quoted 27 lines

drivers/pci/pci-acpi.c +22 -0

+
+	obj = acpi_evaluate_dsm(handle, pci_acpi_dsm_uuid, 3,
+				FUNCTION_DELAY_DSM, NULL);
+	if (!obj)
+		return;
+
+	if (obj->type == ACPI_TYPE_PACKAGE && obj->package.count == 5) {
+		elements = obj->package.elements;
+		if (elements[0].type == ACPI_TYPE_INTEGER) {
+			value = (int)elements[0].integer.value / 1000;
+			if (value < PCI_PM_D3COLD_WAIT)
+				pdev->d3cold_delay = value;
+		}
+		if (elements[3].type == ACPI_TYPE_INTEGER) {
+			value = (int)elements[3].integer.value / 1000;
+			if (value < PCI_PM_D3_WAIT)
+				pdev->d3_delay = value;
+		}
+	}
+	kfree(obj);
+}
+
 static void pci_acpi_setup(struct device *dev)
 {
 	struct pci_dev *pci_dev = to_pci_dev(dev);

drivers/pci/pci-acpi.c static void pci_acpi_setup(struct device *dev) · line 641

Quoted 5 lines

drivers/pci/pci-acpi.c +2 -0

@@ -575,6 +637,9 @@ static void pci_acpi_setup(struct device *dev)
 	if (!adev)
 		return;
 
+	if (pci_dev->pm_cap)
+		pci_acpi_delay_optimize(pci_dev, adev->handle);

Is the "pm_cap" test really necessary? If we do it this way, we then have to convince ourselves that pdev->d3cold_delay and pdev->d3_delay are only needed when pdev has a pm_cap.

If we *always* fill in the delay values, it's possible they won't be used, but we don't have to prove any connection between them and a pm_cap, so the code is easier to analyze.

drivers/pci/pci-acpi.c static void pci_acpi_setup(struct device *dev) · line 641

Quoted 6 lines · Aaron Lu

drivers/pci/pci-acpi.c +2 -0

@@ -575,6 +637,9 @@ static void pci_acpi_setup(struct device *dev)
 	if (!adev)
 		return;
 
+	if (pci_dev->pm_cap)
+		pci_acpi_delay_optimize(pci_dev, adev->handle);

Is the "pm_cap" test really necessary? If we do it this way, we then have to convince ourselves that pdev->d3cold_delay and pdev->d3_delay are only needed when pdev has a pm_cap.

If we *always* fill in the delay values, it's possible they won't be used, but we don't have to prove any connection between them and a pm_cap, so the code is easier to analyze.

According to the PCI firmware spec, there is only one assigned UUID used for PCI system so rename the device_label_dsm_uuid to something more common as: pci_acpi_dsm_uuid and put it in drivers/pci/pci-acpi.c. Make that UUID array extern in the pci-acpi.h so that other code can also make use of it.

This patch shouldn't bring any functional change.

Signed-off-by Aaron Lu <[email protected]>

---
 drivers/pci/pci-acpi.c   |  9 +++++++++
 drivers/pci/pci-label.c  | 11 ++---------
 include/linux/pci-acpi.h |  3 +++
 3 files changed, 14 insertions(+), 9 deletions(-)

drivers/pci/pci-acpi.c +9 -0

index 489063987325..e0afc94aca01 100644
@@ -18,6 +18,15 @@
 #include <linux/pm_qos.h>
 #include "pci.h"
 
+/*
+ * The UUID is defined in the PCI firmware specification available here:
+ * https://www.pcisig.com/members/downloads/pcifw_r3_1_13Dec10.pdf
+ */
+const u8 pci_acpi_dsm_uuid[] = {
+	0xd0, 0x37, 0xc9, 0xe5, 0x53, 0x35, 0x7a, 0x4d,
+	0x91, 0x17, 0xea, 0x4d, 0x19, 0xc3, 0x43, 0x4d
+};
+
 phys_addr_t acpi_pci_root_get_mcfg_addr(acpi_handle handle)
 {
 	acpi_status status = AE_NOT_EXIST;

drivers/pci/pci-label.c +2 -9

index 2ab1b47c7651..024b5c179348 100644
@@ -31,8 +31,6 @@
 #include <linux/pci-acpi.h>
 #include "pci.h"
 
-#define	DEVICE_LABEL_DSM	0x07
-
 #ifdef CONFIG_DMI
 enum smbios_attr_enum {
 	SMBIOS_ATTR_NONE = 0,

@@ -148,11 +146,6 @@ static inline void pci_remove_smbiosname_file(struct pci_dev *pdev)
 #endif
 
 #ifdef CONFIG_ACPI
-static const char device_label_dsm_uuid[] = {
-	0xD0, 0x37, 0xC9, 0xE5, 0x53, 0x35, 0x7A, 0x4D,
-	0x91, 0x17, 0xEA, 0x4D, 0x19, 0xC3, 0x43, 0x4D
-};
-
 enum acpi_attr_enum {
 	ACPI_ATTR_LABEL_SHOW,
 	ACPI_ATTR_INDEX_SHOW,

@@ -179,7 +172,7 @@ static int dsm_get_label(struct device *dev, char *buf,
 	if (!handle)
 		return -1;
 
-	obj = acpi_evaluate_dsm(handle, device_label_dsm_uuid, 0x2,
+	obj = acpi_evaluate_dsm(handle, pci_acpi_dsm_uuid, 0x2,
 				DEVICE_LABEL_DSM, NULL);
 	if (!obj)
 		return -1;

@@ -219,7 +212,7 @@ static bool device_has_dsm(struct device *dev)
 	if (!handle)
 		return false;
 
-	return !!acpi_check_dsm(handle, device_label_dsm_uuid, 0x2,
+	return !!acpi_check_dsm(handle, pci_acpi_dsm_uuid, 0x2,
 				1 << DEVICE_LABEL_DSM);
 }
 

include/linux/pci-acpi.h +3 -0

index 24c7728ca681..3801c704a945 100644
@@ -77,6 +77,9 @@ static inline void acpiphp_remove_slots(struct pci_bus *bus) { }
 static inline void acpiphp_check_host_bridge(struct acpi_device *adev) { }
 #endif
 
+extern const u8 pci_acpi_dsm_uuid[];
+#define DEVICE_LABEL_DSM	0x07
+
 #else	/* CONFIG_ACPI */
 static inline void acpi_pci_add_bus(struct pci_bus *bus) { }
 static inline void acpi_pci_remove_bus(struct pci_bus *bus) { }

Here is an updat, kind of a proof of concept one, to see if it goes the right way:

drivers/pci/host-bridge.c +0 -0

 {
 	struct pci_bus *root_bus = find_pci_root_bus(bus);
 

drivers/pci/pci-acpi.c +11 -0

index e0afc94aca01..04d5b5befbe9 100644
@@ -537,11 +537,32 @@ static struct pci_platform_pm_ops acpi_pci_platform_pm = {
 
 void acpi_pci_add_bus(struct pci_bus *bus)
 {
+	union acpi_object *obj;
+	struct pci_host_bridge *bridge;
+
 	if (acpi_pci_disabled || !bus->bridge)
 		return;
 
 	acpi_pci_slot_enumerate(bus);
 	acpiphp_enumerate_slots(bus);
+
+	/*
+	 * For a host bridge, check its _DSM for function 8 and if
+	 * that is available, mark it in pci_host_bridge.
+	 */
+	if (!pci_is_root_bus(bus))
+		return;
+

drivers/pci/pci-acpi.c +52 -0

 }
 
 void acpi_pci_remove_bus(struct pci_bus *bus)

@@ -567,6 +588,56 @@ static struct acpi_device *acpi_pci_find_companion(struct device *dev)
 				      check_children);
 }
 
+/**
+ * pci_acpi_delay_optimize - optimize PCI D3 and D3cold delay from ACPI
+ * @pdev: the PCI device whose delay is to be updated
+ * @adev: the companion ACPI device of this PCI device
+ *
+ * Update the d3_delay and d3cold_delay of a PCI device from the ACPI _DSM
+ * control method of either its own or its parent bridge.
+ *
+ * The UUID of the _DSM control method, together with other information like
+ * which delay values can be optimized, etc. is defined in a ECN available on
+ * PCIsig.com titled as: ACPI additions for FW latency optimizations.
+ * Function 9 of the ACPI _DSM control method, if available for a specific PCI
+ * device, provides various possible delay values that are less than what the
+ * SPEC requires. Here, we only deal with d3_delay and d3cold_delay. Others
+ * can be added later.
+ * Function 8 of the ACPI _DSM control method, if available for the PCI host
+ * bridge(reflected by the bus' ignore_reset_delay filed), means all its
+ * children devices do not need the reset delay when leaving from D3cold state.
+ */
+static void pci_acpi_delay_optimize(struct pci_dev *pdev,
+				    acpi_handle handle)
+{
+	struct pci_host_bridge *bridge = find_pci_host_bridge(pdev->bus);
+	int value;
+	union acpi_object *obj, *elements;
+
+	if (bridge->ignore_reset_delay)
+		pdev->d3cold_delay = 0;
+
+	obj = acpi_evaluate_dsm(handle, pci_acpi_dsm_uuid, 3,
+				FUNCTION_DELAY_DSM, NULL);
+	if (!obj)
+		return;
+
+	if (obj->type == ACPI_TYPE_PACKAGE && obj->package.count == 5) {
+		elements = obj->package.elements;
+		if (elements[0].type == ACPI_TYPE_INTEGER) {
+			value = (int)elements[0].integer.value / 1000;
+			if (value < PCI_PM_D3COLD_WAIT)
+				pdev->d3cold_delay = value;
+		}
+		if (elements[3].type == ACPI_TYPE_INTEGER) {
+			value = (int)elements[3].integer.value / 1000;
+			if (value < PCI_PM_D3_WAIT)
+				pdev->d3_delay = value;
+		}
+	}
+	ACPI_FREE(obj);
+}
+
 static void pci_acpi_setup(struct device *dev)
 {
 	struct pci_dev *pci_dev = to_pci_dev(dev);

@@ -575,6 +646,8 @@ static void pci_acpi_setup(struct device *dev)
 	if (!adev)
 		return;
 
+	pci_acpi_delay_optimize(pci_dev, adev->handle);
+
 	pci_acpi_add_pm_notifier(adev, pci_dev);
 	if (!adev->wakeup.flags.valid)
 		return;

drivers/pci/pci.h +2 -0

index 4091f82239cd..802e7c0c7f9f 100644
@@ -321,4 +321,6 @@ static inline int pci_dev_specific_reset(struct pci_dev *dev, int probe)
 }
 #endif
 
+struct pci_host_bridge *find_pci_host_bridge(struct pci_bus *bus);
+
 #endif /* DRIVERS_PCI_H */

include/linux/pci-acpi.h +2 -0

index 3801c704a945..a965efa52152 100644
@@ -79,6 +79,8 @@ static inline void acpiphp_check_host_bridge(struct acpi_device *adev) { }
 
 extern const u8 pci_acpi_dsm_uuid[];
 #define DEVICE_LABEL_DSM	0x07
+#define RESET_DELAY_DSM		0x08
+#define FUNCTION_DELAY_DSM	0x09
 
 #else	/* CONFIG_ACPI */
 static inline void acpi_pci_add_bus(struct pci_bus *bus) { }

include/linux/pci.h +0 -0

index a379513bddef..e587832885e9 100644

include/linux/pci.h +0 -0

 };
 
 #define	to_pci_host_bridge(n) container_of(n, struct pci_host_bridge, dev)

Signature · 1 line

2.1.0

Quoted 12 lines · Bjorn Helgaas

drivers/pci/pci-acpi.c static void pci_acpi_setup(struct device *dev) · line 641

Quoted 6 lines · Aaron Lu

drivers/pci/pci-acpi.c +2 -0

@@ -575,6 +637,9 @@ static void pci_acpi_setup(struct device *dev)
 	if (!adev)
 		return;
 
+	if (pci_dev->pm_cap)
+		pci_acpi_delay_optimize(pci_dev, adev->handle);

Is the "pm_cap" test really necessary? If we do it this way, we then have to convince ourselves that pdev->d3cold_delay and pdev->d3_delay are only needed when pdev has a pm_cap.

Quoted 3 lines

If we *always* fill in the delay values, it's possible they won't be used, but we don't have to prove any connection between them and a pm_cap, so the code is easier to analyze.

I remembered why I did the pm_cap test: the d3cold_delay and d3_delay is only filled when pm_cap is set in pci_pm_init - if the device doesn't have PCI_CAP_ID_PM set, its pm_cap will be 0 and d3cold_delay, d3_delay will not be assigned.

Here is v3, changes from v2 are:
- Patch 1/3: add Rafael's acked-by tag;
- Patch 2/3: newly introduced, to rename find_pci_host_bridge and export it
- Patch 3/3: address Bjorn's comments for v2

Thanks a lot for your suggestions and review!

Regards,
Aaron

Here is v3, changes from v2 are:
- Patch 1/3: add Rafael's acked-by tag;
- Patch 2/3: newly introduced, to rename find_pci_host_bridge and export it
- Patch 3/3: address Bjorn's comments for v2