ARM: dts: specify all the per-cpu interrupts of arch timer for exynos5440

From: Thomas Abraham <[email protected]>

Need to be changed requirements in the 'cpus' node for exynos5440 to specify all the per-cpu interrupts of arch timer.

Signed-off-by Thomas Abraham <[email protected]>

Signed-off-by Kukjin Kim <[email protected]>

---
 arch/arm/boot/dts/exynos5440.dtsi |   20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

arch/arm/boot/dts/exynos5440.dtsi +0 -0

index 5406689..c5bd8ed 100644

arch/arm/boot/dts/exynos5440.dtsi +12 -3

 				clock-frequency = <1000000>;
 			};
 		};

@@ -36,7 +39,10 @@
 			compatible = "arm,cortex-a15";
 			timer {
 				compatible = "arm,armv7-timer";
-				interrupts = <1 14 0xf08>;
+				interrupts = <1 13 0xf08>;
+					     <1 14 0xf08>,
+					     <1 11 0xf08>,
+					     <1 10 0xf08>;
 				clock-frequency = <1000000>;
 			};
 		};

@@ -44,7 +50,10 @@
 			compatible = "arm,cortex-a15";
 			timer {
 				compatible = "arm,armv7-timer";
-				interrupts = <1 14 0xf08>;
+				interrupts = <1 13 0xf08>;
+					     <1 14 0xf08>,
+					     <1 11 0xf08>,
+					     <1 10 0xf08>;
 				clock-frequency = <1000000>;
 			};
 		};

@@ -52,7 +61,10 @@
 			compatible = "arm,cortex-a15";
 			timer {
 				compatible = "arm,armv7-timer";
-				interrupts = <1 14 0xf08>;
+				interrupts = <1 13 0xf08>;
+					     <1 14 0xf08>,
+					     <1 11 0xf08>,
+					     <1 10 0xf08>;
 				clock-frequency = <1000000>;
 			};
 		};

Signature · 7 lines

1.7.10.4


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Quoted 4 lines

From: Thomas Abraham <[email protected]>

Need to be changed requirements in the 'cpus' node for exynos5440 to specify all the per-cpu interrupts of arch timer.

The node(s) for the arch timer should not be in the cpus/cpu at N nodes. Instead, there should be one node (in the root of the tree).

If this works currently it's only because the driver picks up one of the

and luckily it's the same as the others. This is not guaranteed to work in future, and will likely break.

Review

Quoted 8 lines

Signed-off-by Thomas Abraham <[email protected]>

Signed-off-by Kukjin Kim <[email protected]>

---
 arch/arm/boot/dts/exynos5440.dtsi |   20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

(quoted diff) +0 -0

b/arch/arm/boot/dts/exynos5440.dtsi

arch/arm/boot/dts/exynos5440.dtsi line 34

Quoted 12 lines

index 5406689..c5bd8ed 100644

arch/arm/boot/dts/exynos5440.dtsi +4 -1

@@ -28,7 +28,10 @@
 			compatible = "arm,cortex-a15";
 			timer {
 				compatible = "arm,armv7-timer";
-				interrupts = <1 13 0xf08>;
+				interrupts = <1 13 0xf08>,
+					     <1 14 0xf08>,
+					     <1 11 0xf08>,
+					     <1 10 0xf08>;

Also, this interrupts list is updated differently to all the other nodes.

Quoted 1 line · Mark Rutland

+ devicetree-discuss, Grant Likely, Rob Herring and Tony Lindgren

Quoted 9 lines · Kukjin Kim

Quoted 4 lines

From: Thomas Abraham <[email protected]>

Need to be changed requirements in the 'cpus' node for exynos5440 to specify all the per-cpu interrupts of arch timer.

The node(s) for the arch timer should not be in the cpus/cpu at N nodes. Instead, there should be one node (in the root of the tree).

Well, I don't think so. As per my understanding, the local timers are attached to every ARM cores (cpus) and it generates certain interrupt to the GIC. So the correct representation for this in device tree is to include the interrupts in the cpu nodes in dts file. Your comments refer to a limitation in the Linux kernel implementation of the arch_timer and it should not result in representing the hardware details incorrectly in the dts file.

Quoted 2 lines

If this works currently it's only because the driver picks up one of the

nodes,

Quoted 3 lines

and luckily it's the same as the others. This is not guaranteed to work in future, and will likely break.

It is up to the Linux kernel implementation of arch_timer to handle the hardware details in dts file accordingly.

Quoted 10 lines

Review

Quoted 9 lines

Signed-off-by Thomas Abraham <[email protected]>

Signed-off-by Kukjin Kim <[email protected]>

---
 arch/arm/boot/dts/exynos5440.dtsi |   20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

(quoted diff) +0 -0

b/arch/arm/boot/dts/exynos5440.dtsi

Quoted 14 lines

arch/arm/boot/dts/exynos5440.dtsi line 34

Quoted 12 lines

index 5406689..c5bd8ed 100644

arch/arm/boot/dts/exynos5440.dtsi +4 -1

@@ -28,7 +28,10 @@
 			compatible = "arm,cortex-a15";
 			timer {
 				compatible = "arm,armv7-timer";
-				interrupts = <1 13 0xf08>;
+				interrupts = <1 13 0xf08>,
+					     <1 14 0xf08>,
+					     <1 11 0xf08>,
+					     <1 10 0xf08>;

Also, this interrupts list is updated differently to all the other nodes.

Typo?

Quoted 1 line

Hmm, I think this should be fine. If any concerns, please let me know in detail.

[...]

Thanks.

- Kukjin

Quoted 13 lines · Kukjin Kim

Quoted 1 line · Mark Rutland

+ devicetree-discuss, Grant Likely, Rob Herring and Tony Lindgren

Quoted 9 lines · Kukjin Kim

Quoted 4 lines

From: Thomas Abraham <[email protected]>

Need to be changed requirements in the 'cpus' node for exynos5440 to specify all the per-cpu interrupts of arch timer.

The node(s) for the arch timer should not be in the cpus/cpu@N nodes. Instead, there should be one node (in the root of the tree).

Quoted 7 lines

Well, I don't think so. As per my understanding, the local timers are attached to every ARM cores (cpus) and it generates certain interrupt to the GIC. So the correct representation for this in device tree is to include the interrupts in the cpu nodes in dts file. Your comments refer to a limitation in the Linux kernel implementation of the arch_timer and it should not result in representing the hardware details incorrectly in the dts file.

I disagree. The "correct representation" is whatever the devicetree binding documentation describes. It does not describe placing timer nodes in the cpu nodes.

Looping Marc, Benoit

Quoted 25 lines · Mark Rutland

Quoted 13 lines · Kukjin Kim

Quoted 1 line · Mark Rutland

+ devicetree-discuss, Grant Likely, Rob Herring and Tony Lindgren

Quoted 9 lines · Kukjin Kim

Quoted 4 lines

From: Thomas Abraham <[email protected]>

Need to be changed requirements in the 'cpus' node for exynos5440 to specify all the per-cpu interrupts of arch timer.

The node(s) for the arch timer should not be in the cpus/cpu at N nodes. Instead, there should be one node (in the root of the tree).

Quoted 10 lines

Well, I don't think so. As per my understanding, the local timers are attached to every ARM cores (cpus) and it generates certain interrupt to the
GIC. So the correct representation for this in device tree is to include the
interrupts in the cpu nodes in dts file. Your comments refer to a limitation in the Linux kernel implementation of the arch_timer and it should not result in representing the hardware details incorrectly in the
dts file.

Quoted 6 lines

I disagree. The "correct representation" is whatever the devicetree binding
documentation describes. It does not describe placing timer nodes in the cpu
nodes.

This seems to be exact same topic what is getting discussed here [1] Technically DT is suppose to represent how the hardware is rather than how the bindings are done.

But as Marc pointed out, the approach taken currently is to not duplicate the banked information. The thread [1] isn't concluded yet but looks like we might want to avoid duplicating the information considering, more of such duplication needs to follow. e.g gic i/f

Am still waiting on what Benoit has to say ?

Hi Santosh,

Quoted 38 lines · Santosh Shilimkar

Looping Marc, Benoit

Quoted 25 lines · Mark Rutland

Quoted 13 lines · Kukjin Kim

Quoted 1 line · Mark Rutland

+ devicetree-discuss, Grant Likely, Rob Herring and Tony Lindgren

Quoted 9 lines · Kukjin Kim

Quoted 4 lines

From: Thomas Abraham <[email protected]>

Need to be changed requirements in the 'cpus' node for exynos5440 to specify all the per-cpu interrupts of arch timer.

The node(s) for the arch timer should not be in the cpus/cpu at N nodes. Instead, there should be one node (in the root of the tree).

Quoted 10 lines

Well, I don't think so. As per my understanding, the local timers are attached to every ARM cores (cpus) and it generates certain interrupt to the
GIC. So the correct representation for this in device tree is to include the
interrupts in the cpu nodes in dts file. Your comments refer to a limitation in the Linux kernel implementation of the arch_timer and it should not result in representing the hardware details incorrectly in the
dts file.

Quoted 6 lines

I disagree. The "correct representation" is whatever the devicetree binding
documentation describes. It does not describe placing timer nodes in the cpu
nodes.

This seems to be exact same topic what is getting discussed here [1] Technically DT is suppose to represent how the hardware is rather than how the bindings are done.

Quoted 6 lines

But as Marc pointed out, the approach taken currently is to not duplicate the banked information. The thread [1] isn't concluded yet but looks like we might want to avoid duplicating the information considering, more of such duplication needs to follow. e.g gic i/f

Am still waiting on what Benoit has to say ?

I agree with you :-)

I'm not sure the binding was properly done to reflect the HW accurately.

A local timer for my point of view should be located in the cpu node like a L1 cache. Or at least referenced in each cpu by a phandle.

What was the rational to put it in the root?

Hi Santosh,

Quoted 38 lines · Santosh Shilimkar

Looping Marc, Benoit

Quoted 25 lines · Mark Rutland

Quoted 13 lines · Kukjin Kim

Quoted 1 line · Mark Rutland

+ devicetree-discuss, Grant Likely, Rob Herring and Tony Lindgren

Quoted 9 lines · Kukjin Kim

Quoted 4 lines

From: Thomas Abraham <[email protected]>

Need to be changed requirements in the 'cpus' node for exynos5440 to specify all the per-cpu interrupts of arch timer.

The node(s) for the arch timer should not be in the cpus/cpu at N nodes. Instead, there should be one node (in the root of the tree).

Quoted 10 lines

Well, I don't think so. As per my understanding, the local timers are attached to every ARM cores (cpus) and it generates certain interrupt to the
GIC. So the correct representation for this in device tree is to include the
interrupts in the cpu nodes in dts file. Your comments refer to a limitation in the Linux kernel implementation of the arch_timer and it should not result in representing the hardware details incorrectly in the
dts file.

Quoted 6 lines

I disagree. The "correct representation" is whatever the devicetree binding
documentation describes. It does not describe placing timer nodes in the cpu
nodes.

This seems to be exact same topic what is getting discussed here [1] Technically DT is suppose to represent how the hardware is rather than how the bindings are done.

Quoted 6 lines

But as Marc pointed out, the approach taken currently is to not duplicate the banked information. The thread [1] isn't concluded yet but looks like we might want to avoid duplicating the information considering, more of such duplication needs to follow. e.g gic i/f

Am still waiting on what Benoit has to say ?

I agree with you :-)

I'm not sure the binding was properly done to reflect the HW accurately.

A local timer for my point of view should be located in the cpu node like a L1 cache. Or at least referenced in each cpu by a phandle.

What was the rational to put it in the root?

Hi Benoit,

Quoted 48 lines · Benoit Cousson

Hi Santosh,

Quoted 38 lines · Santosh Shilimkar

Looping Marc, Benoit

Quoted 25 lines · Mark Rutland

Quoted 13 lines · Kukjin Kim

Quoted 1 line · Mark Rutland

+ devicetree-discuss, Grant Likely, Rob Herring and Tony Lindgren

Quoted 9 lines · Kukjin Kim

Quoted 4 lines

From: Thomas Abraham <[email protected]>

Need to be changed requirements in the 'cpus' node for exynos5440 to specify all the per-cpu interrupts of arch timer.

The node(s) for the arch timer should not be in the cpus/cpu@N nodes. Instead, there should be one node (in the root of the tree).

Quoted 10 lines

Well, I don't think so. As per my understanding, the local timers are attached to every ARM cores (cpus) and it generates certain interrupt to the
GIC. So the correct representation for this in device tree is to include the
interrupts in the cpu nodes in dts file. Your comments refer to a limitation in the Linux kernel implementation of the arch_timer and it should not result in representing the hardware details incorrectly in the
dts file.

Quoted 6 lines

I disagree. The "correct representation" is whatever the devicetree binding
documentation describes. It does not describe placing timer nodes in the cpu
nodes.

This seems to be exact same topic what is getting discussed here [1] Technically DT is suppose to represent how the hardware is rather than how the bindings are done.

Quoted 6 lines

But as Marc pointed out, the approach taken currently is to not duplicate the banked information. The thread [1] isn't concluded yet but looks like we might want to avoid duplicating the information considering, more of such duplication needs to follow. e.g gic i/f

Am still waiting on what Benoit has to say ?

Quoted 8 lines

I agree with you :-)

I'm not sure the binding was properly done to reflect the HW accurately.

A local timer for my point of view should be located in the cpu node like a L1 cache. Or at least referenced in each cpu by a phandle.

What was the rational to put it in the root?

The rational was to follow what we already do for most (all?) banked resources. We already have TWD, GIC and PMU that have a root node, avoiding duplicated resources. I think consistency is an important thing to have.

If we decide to move everything into CPU nodes and duplicate all the banked resources, fine. But that has impacts that reach far beyond the simple case of the timer.

In particular, good luck with the GIC distributor interface, where the 32 first interrupts are per CPU. This would also mandate a redesign of the way we specify a PPI, as the CPU mask in the third field doesn't mean a thing anymore.

If you insist on having a phandle to a timer node, fine by me.

Benoit,

Quoted 15 lines · Marc Zyngier

Hi Benoit,

Quoted 12 lines · Benoit Cousson

Hi Santosh,

Quoted 9 lines · Santosh Shilimkar

Looping Marc, Benoit

Quoted 6 lines · Mark Rutland

Quoted 5 lines · Kukjin Kim

Quoted 1 line · Mark Rutland

+ devicetree-discuss, Grant Likely, Rob Herring and Tony Lindgren

Quoted 1 line · Kukjin Kim

Quoted 3 lines

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From: Thomas Abraham <[email protected]>

Need to be changed requirements in the 'cpus' node for

exynos5440

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to specify all the per-cpu interrupts of arch timer.

The node(s) for the arch timer should not be in the cpus/cpu at N

nodes.

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Instead, there should be one node (in the root of the tree).

Well, I don't think so. As per my understanding, the local timers

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attached to every ARM cores (cpus) and it generates certain

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to the
GIC. So the correct representation for this in device tree is to include the
interrupts in the cpu nodes in dts file. Your comments refer to a limitation in the Linux kernel implementation of the arch_timer and

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should not result in representing the hardware details incorrectly

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the
dts file.

I disagree. The "correct representation" is whatever the devicetree binding
documentation describes. It does not describe placing timer nodes in the cpu
nodes.

This seems to be exact same topic what is getting discussed here [1] Technically DT is suppose to represent how the hardware is rather than how the bindings are done.

But as Marc pointed out, the approach taken currently is to not duplicate the banked information. The thread [1] isn't concluded yet but looks like we might want to avoid duplicating the information considering, more of such duplication needs to follow. e.g gic i/f

Quoted 5 lines

Quoted 5 lines

Quoted 1 line

Am still waiting on what Benoit has to say ?

I agree with you :-)

I'm not sure the binding was properly done to reflect the HW

Quoted 20 lines

Quoted 5 lines

A local timer for my point of view should be located in the cpu node like a L1 cache. Or at least referenced in each cpu by a phandle.

What was the rational to put it in the root?

The rational was to follow what we already do for most (all?) banked resources. We already have TWD, GIC and PMU that have a root node, avoiding duplicated resources. I think consistency is an important thing to have.

If we decide to move everything into CPU nodes and duplicate all the banked resources, fine. But that has impacts that reach far beyond the simple case of the timer.

In particular, good luck with the GIC distributor interface, where the 32 first interrupts are per CPU. This would also mandate a redesign of the way we specify a PPI, as the CPU mask in the third field doesn't mean a thing anymore.

Quoted 2 lines

If you insist on having a phandle to a timer node, fine by me.

Can you please comment on it so that we can conclude this thread ? I would like to update my patches and hence the push.

Quoted 13 lines · Kukjin Kim

Quoted 1 line · Mark Rutland

+ devicetree-discuss, Grant Likely, Rob Herring and Tony Lindgren

Quoted 9 lines · Kukjin Kim

Quoted 4 lines

From: Thomas Abraham <[email protected]>

Need to be changed requirements in the 'cpus' node for exynos5440 to specify all the per-cpu interrupts of arch timer.

The node(s) for the arch timer should not be in the cpus/cpu at N nodes. Instead, there should be one node (in the root of the tree).

Quoted 7 lines

Well, I don't think so. As per my understanding, the local timers are attached to every ARM cores (cpus) and it generates certain interrupt to the GIC. So the correct representation for this in device tree is to include the interrupts in the cpu nodes in dts file. Your comments refer to a limitation in the Linux kernel implementation of the arch_timer and it should not result in representing the hardware details incorrectly in the dts file.

I disagree. The "correct representation" is whatever the devicetree binding documentation describes. It does not describe placing timer nodes in the cpu nodes.

Quoted 6 lines

Quoted 2 lines

If this works currently it's only because the driver picks up one of the

nodes,

Quoted 3 lines

and luckily it's the same as the others. This is not guaranteed to work in future, and will likely break.

Quoted 2 lines

It is up to the Linux kernel implementation of arch_timer to handle the hardware details in dts file accordingly.

The binding specification does not specify that there should be multiple timer nodes, nor does it specify that they should be under cpu nodes. The timers, being a banked resource, can be described with one node.

It is not up to the Linux kernel to handle undocumented variations of bindings.