Apple SPI properties

Fabricated devices such as LNXPWRBN lack a handle, causing evaluation of _CCA and _DSD to always fail with AE_BAD_PARAMETER. While that is merely a (negligible) waste of processing power, evaluating a _DSM for them (such as Apple's device properties _DSM which we're about to add) results in an ugly error:

    ACPI: \: failed to evaluate _DSM (0x1001)

Avoid by not evaluating _DSD and the upcoming _DSM for devices without handle.

Cc Rafael J. Wysocki <[email protected]>

Cc Mika Westerberg <[email protected]>

SPI and I2C slaves are enumerated by their respective parents rather than the ACPI core. They are recognized by presence of _CRS resources, which however are missing on Macs. Check for presence of device properties instead.

Cc Rafael J. Wysocki <[email protected]>

Cc Mika Westerberg <[email protected]>

Cc Andy Shevchenko <[email protected]>

Cc Federico Lorenzi <[email protected]>

Reported-and-tested-by Ronald Tschalär <[email protected]>

Signed-off-by Lukas Wunner <[email protected]>

---
Changes v1 -> v2:
- Newly inserted patch in v2 to fix an enumeration issue. (Ronald)

 drivers/acpi/scan.c | 6 ++++++
 1 file changed, 6 insertions(+)

drivers/acpi/scan.c +0 -0

index d4ff2cd1f738..c565e74bd2dd 100644

drivers/acpi/scan.c +4 -0

+	    (device_property_present(&device->dev, "spiSclkPeriod") ||
+	     device_property_present(&device->dev, "i2cAddress")))
+		return true;
+
 	INIT_LIST_HEAD(&resource_list);
 	acpi_dev_get_resources(device, &resource_list, acpi_check_spi_i2c_slave,
 			       &is_spi_i2c_slave);

Signature · 1 line

2.11.0

drivers/acpi/scan.c static bool acpi_is_spi_i2c_slave(struct acpi_device *device) · line 1448

Quoted 8 lines · Lukas Wunner

drivers/acpi/scan.c +2 -0

@@ -1444,6 +1444,12 @@ static bool acpi_is_spi_i2c_slave(struct acpi_device *device)
 	struct list_head resource_list;
 	bool is_spi_i2c_slave = false;
 
+	/* Macs use device properties in lieu of _CRS resources */
+	if (IS_ENABLED(CONFIG_X86) && dmi_match(DMI_SYS_VENDOR, "Apple Inc.") &&

Do we really need these checks?

Quoted 10 lines

drivers/acpi/scan.c +4 -0

+	    (device_property_present(&device->dev, "spiSclkPeriod") ||
+	     device_property_present(&device->dev, "i2cAddress")))
+		return true;
+
 	INIT_LIST_HEAD(&resource_list);
 	acpi_dev_get_resources(device, &resource_list, acpi_check_spi_i2c_slave,
 			       &is_spi_i2c_slave);

Signature · 1 line

2.11.0

Quoted 7 lines · Mika Westerberg

Quoted 6 lines · Lukas Wunner

drivers/acpi/scan.c +0 -0

@@ -1444,6 +1444,12 @@ static bool acpi_is_spi_i2c_slave(struct acpi_device *device)
 	struct list_head resource_list;
 	bool is_spi_i2c_slave = false;
 

Quoted 4 lines

drivers/acpi/scan.c static bool acpi_is_spi_i2c_slave(struct acpi_device *device) · line 1448

Quoted 2 lines

drivers/acpi/scan.c +2 -0

+	/* Macs use device properties in lieu of _CRS resources */
+	if (IS_ENABLED(CONFIG_X86) && dmi_match(DMI_SYS_VENDOR, "Apple Inc.") &&

Do we really need these checks?

With these checks present, searching for the properties can be optimized away on ARM and skipped on x86 non-Macs. (Each property query requires decoding the _DSD Package and performing an O(n) search of the properties.)

MacBooks and MacBook Pros introduced since 2015 return empty _CRS data for SPI slaves, causing device initialization to fail. Most of the information that would normally be conveyed via _CRS is available through ACPI device properties instead, so take advantage of them.

+ spi->mode |= SPI_LSB_FIRST;

MacBooks and MacBook Pros introduced since 2015 return empty _CRS data for SPI slaves, causing device initialization to fail. Most of the information that would normally be conveyed via _CRS is available through ACPI device properties instead, so take advantage of them.

The meaning and appropriate usage of the device properties was reverse engineered by Ronald Tschalär and carried over from these commits authored by him:

https://github.com/cb22/macbook12-spi-driver/commit/9a416d699ef4
https://github.com/cb22/macbook12-spi-driver/commit/0c34936ed9a1

According to Ronald, the device properties have the following meaning:

spiSclkPeriod   /* period in ns */
spiWordSize     /* in number of bits */
spiBitOrder     /* 1 = MSB_FIRST, 0 = LSB_FIRST */
spiSPO          /* clock polarity: 0 = low, 1 = high */
spiSPH          /* clock phase: 0 = first, 1 = second */
spiCSDelay      /* delay between cs and receive on reads in 10 us */
resetA2RUsec    /* active-to-receive delay? */
resetRecUsec    /* receive delay? */

Cc Mark Brown <[email protected]>

Cc Federico Lorenzi <[email protected]>

Reported-by Leif Liddy <[email protected]>

Tested-by Ronald Tschalär <[email protected]>

Signed-off-by Lukas Wunner <lukas-JFq808J9C/[email protected]>

While the rest of the world has standardized on _DSD as the way to store device properties in AML (introduced with ACPI 5.1 in 2014), Apple has been using a custom _DSM to achieve the same for much longer (ever since they switched from DeviceTree-based PowerPC to Intel in 2005, verified with MacOS X 10.4.11).

drivers/acpi/property.c +9 -0

+/**
+ * acpi_retrieve_apple_properties - retrieve and convert Apple _DSM properties
+ * @adev: ACPI device for which to retrieve the properties
+ *
+ * Invoke Apple's custom _DSM once to check the protocol version and once more
+ * to retrieve the properties.  They are marshalled up in a single package as
+ * alternating key/value elements, unlike _DSD which stores them as a package
+ * of 2-element packages.  Convert to _DSD format and make them available under
+ * the primary fwnode.

drivers/acpi/property.c +29 -0

+       /* newsize = key length + value length of each tuple */
+       numprops = props->package.count / 2;
+       for (i = 0; i < numprops; i++) {
+               union acpi_object *key = &props->package.elements[i * 2];
+               union acpi_object *val = &props->package.elements[i * 2 + 1];
+
+               if ( key->type != ACPI_TYPE_STRING ||
+                   (val->type != ACPI_TYPE_INTEGER &&
+                    val->type != ACPI_TYPE_BUFFER)) {
+                       key->type = ACPI_TYPE_ANY; /* mark as to be skipped */
+                       skipped++;
+                       continue;
+               }
+               newsize += key->string.length + 1;
+               if ( val->type == ACPI_TYPE_BUFFER)
+                       newsize += val->buffer.length;
+       }
+
+       if (skipped)
+               acpi_handle_info(adev->handle, FW_INFO
+                                "skipped %u properties: wrong type\n",
+                                skipped);
+       if (skipped == numprops)
+               goto out_free;
+
+       /* newsize += top-level package + 3 objects for each key/value tuple */
+       newsize += (1 + 3 * (numprops - skipped)) * sizeof(union acpi_object);
+       newprops = ACPI_ALLOCATE_ZEROED(newsize);
+       if (!newprops)

drivers/acpi/property.c +6 -0

+
+               newprops[1 + j].type = ACPI_TYPE_PACKAGE;
+               newprops[1 + j].package.count = 2;
+               newprops[1 + j].package.elements = &newprops[k];
+
+               newprops[k].type = ACPI_TYPE_STRING;

drivers/acpi/property.c +8 -0

+                       newprops[v].buffer.length = val->buffer.length;
+                       newprops[v].buffer.pointer = free_space;
+                       memcpy(free_space, val->buffer.pointer,
+                              val->buffer.length);
+                       free_space += val->buffer.length;
+               }
 
+               j++; /* not incremented for skipped properties */
 
+       }

Quoted 5 lines · Lukas Wunner

While the rest of the world has standardized on _DSD as the way to store device properties in AML (introduced with ACPI 5.1 in 2014), Apple has been using a custom _DSM to achieve the same for much longer (ever since they switched from DeviceTree-based PowerPC to Intel in 2005, verified with MacOS X 10.4.11).

drivers/acpi/property.c static const u8 ads_uuid[16] = { · line 61

Quoted 8 lines

drivers/acpi/property.c +8 -0

+static void acpi_retrieve_apple_properties(struct acpi_device *adev)
+{
+       unsigned int i, j, newsize = 0, numprops, skipped = 0;
+       union acpi_object *props, *newprops;
+       void *free_space;
+
+       if (!IS_ENABLED(CONFIG_X86) || !dmi_match(DMI_SYS_VENDOR, "Apple Inc."))
+               return;

You are using this in few places, perhaps it makes sense to do in (maybe) header like
drivers/acpi/apple.h

static inline bool is_apple_system(void)

{
   return IS_ENABLED(CONFIG_X86) && dmi_match(DMI_SYS_VENDOR, "Apple Inc.");
}

I know this makes more LOCs, the rationale is to keep such deterministic things in one place (basically maintenance).

Quoted 6 lines · Andy Shevchenko

Quoted 5 lines · Lukas Wunner

While the rest of the world has standardized on _DSD as the way to store device properties in AML (introduced with ACPI 5.1 in 2014), Apple has been using a custom _DSM to achieve the same for much longer (ever since they switched from DeviceTree-based PowerPC to Intel in 2005, verified with MacOS X 10.4.11).

[snip]

Quoted 13 lines

drivers/acpi/property.c static const u8 ads_uuid[16] = { · line 61

Quoted 8 lines

drivers/acpi/property.c +8 -0

+static void acpi_retrieve_apple_properties(struct acpi_device *adev)
+{
+       unsigned int i, j, newsize = 0, numprops, skipped = 0;
+       union acpi_object *props, *newprops;
+       void *free_space;
+
+       if (!IS_ENABLED(CONFIG_X86) || !dmi_match(DMI_SYS_VENDOR, "Apple Inc."))
+               return;

You are using this in few places, perhaps it makes sense to do in (maybe) header like
drivers/acpi/apple.h

Quoted 7 lines

static inline bool is_apple_system(void)

{
   return IS_ENABLED(CONFIG_X86) && dmi_match(DMI_SYS_VENDOR, "Apple Inc.");
}

I know this makes more LOCs, the rationale is to keep such deterministic things in one place (basically maintenance).

You mean like is_uv_system() for SGI UltraViolet?

I could add a global bool is_apple_system which is set early during boot, then the DMI check would only have to be performed once. The bool would be #defined to false on non-x86 arches via a header file which would have to live in include/linux/. I could add an x86-specific config option such as CONFIG_X86_APPLE which would allow removal of all Mac-specific quirks and behaviour by likewise #defining is_apple_system to false.

I'm not sure if the x86 maintainers will approve of this. Next thing you know, someone wants to add the same thing for Dell or whatever. OTOH the amount of code to deal with Apple quirks may justify it. Adding x86 maintainers to cc. Ingo, Thomas, Peter, any opinion?

My concern is that this series is bikeshedded / postponed indefinitely if it is made to depend on such bigger changes. (The discussion of which is legitimate of course.)

While the rest of the world has standardized on _DSD as the way to store device properties in AML (introduced with ACPI 5.1 in 2014), Apple has been using a custom _DSM to achieve the same for much longer (ever since they switched from DeviceTree-based PowerPC to Intel in 2005, verified with MacOS X 10.4.11).

The theory of operation on macOS is as follows: AppleACPIPlatform.kext invokes mergeEFIproperties() and mergeDSMproperties() for each device to merge properties conveyed by EFI drivers as well as properties stored in AML into the I/O Kit registry from which they can be retrieved by drivers. We've been supporting EFI properties since commit 58c5475aba67 ("x86/efi: Retrieve and assign Apple device properties"). The present commit adds support for _DSM properties, thereby completing our support for Apple device properties. The _DSM properties are made available under the primary fwnode, the EFI properties under the secondary fwnode. So for devices which possess both property types, they can all be elegantly accessed with the uniform API in <linux/property.h>.

Until recently we had no need to support _DSM properties, they contained only uninteresting garbage. The situation has changed with MacBooks and MacBook Pros introduced since 2015: Their keyboard is attached with SPI instead of USB and the _CRS data which is necessary to initialize the spi driver only contains valid information if OSPM responds "false" to _OSI("Darwin"). If OSPM responds "true", _CRS is empty and the spi driver fails to initialize. The rationale is very simple, Apple only cares about macOS and Windows: On Windows, _CRS contains valid data, whereas on macOS it is empty. Instead, macOS gleans the necessary data from the _DSM properties.

Since Linux deliberately defaults to responding "true" to _OSI("Darwin"), we need to emulate macOS' behaviour by initializing the spi driver with data returned by the _DSM.

An out-of-tree driver for the SPI keyboard exists which currently binds to the ACPI device, invokes the _DSM, parses the returned package and instantiates an SPI device with the data gleaned from the _DSM:
https://github.com/cb22/macbook12-spi-driver/commit/9a416d699ef4
https://github.com/cb22/macbook12-spi-driver/commit/0c34936ed9a1

By adding support for Apple's _DSM properties in generic ACPI code, the out-of-tree driver will be able to register as a regular SPI device, significantly reducing its amount of code and improving its chances to be mainlined.

The SPI keyboard will not be the only user of this commit: E.g. on the MacBook8,1, the UART-attached Bluetooth device likewise returns empty _CRS data if OSPM returns "true" to _OSI("Darwin").

The _DSM returns a Package whose format unfortunately deviates slightly from the _DSD spec: The properties are marshalled up in a single Package as alternating key/value elements, unlike _DSD which stores them as a Package of 2-element Packages. The present commit therefore converts the Package to _DSD format and the ACPI core can then treat the data as if Apple would follow the standard.

Well, except for one small annoyance: The properties returned by the _DSM only ever have one of two types, Integer or Buffer. The former is retrievable as usual with device_property_read_u64(), but the latter is not part of the _DSD spec and it is not possible to retrieve Buffer properties with the device_property_read_*() functions due to the type checking performed in drivers/acpi/property.c. It is however possible to retrieve them with acpi_dev_get_property(). Apple is using the Buffer type somewhat sloppily to store null-terminated strings but also integers. The real data type is not distinguishable by the ACPI core and the onus is on the caller to use the contents of the Buffer in an appropriate way.

In case Apple moves to _DSD in the future, this commit first checks for _DSD and falls back to _DSM only if _DSD is not found.

Cc Rafael J. Wysocki <[email protected]>

Cc Mika Westerberg <[email protected]>