ARM: OMAP2+: omap_device: drop broken RPM status update from suspend_noirq

Since commit a8636c89648a ("PM / Runtime: Don't allow to suspend a device with an active child"), which went into 4.10, it is no longer permitted to set RPM_SUSPENDED state for a device with active children (unless power.ignore_children is set).

This specifically means that the attempts to do just that from the omap pm-domain suspend_noirq callback have since been failing whenever a child is active, for example:

am335x-usb-childs 47400000.usb: runtime PM trying to suspend
device but active child

Silence this warning by dropping the broken pm_runtime_set_suspended() call from the omap suspend_noirq callback along with the redundant pm_runtime_set_active() in resume_noirq.

This effectively reverts commit 3522bf7bfa24 ("ARM: OMAP2+: omap_device:
maintain sane runtime pm status around suspend/resume"), which started updating the RPM state after the runtime_suspend callback (!) for active omap devices had been called during system suspend. The rationale was that a later pm_runtime_get_sync() would then fail (even after runtime pm had been disabled) and that this in turn would avoid any external aborts when accessing registers with clocks disabled. (See also commit 6f3c77b040fc ("PM / Runtime: let rpm_resume() succeed if RPM_ACTIVE, even when disabled, v2").

But during the suspend_noirq phase all children would already have been suspended and their drivers would specifically not attempt any further register accesses. And if this was all just a workaround for random device drivers doing cross-tree calls during system suspend, those drivers should be fixed and updated to explicitly model such dependencies using device-links instead (and either way, any such calls have been causing crashes since 4.10).

From 05cd6c19f898ca28480b9ca8dca5b987190351d9 Mon Sep 17 00:00:00 2001

My personal thought here is that removing of pm_runtime_set_active() will not fix root cause of the problem, but rather hide it :( and, probably, real fix will be to update USB framework to ensure that all suspend devices are also PM runtime suspend (not sure how) or add few more pm_suspend_ignore_children() calls
(for example as I've tried to do in [2], but this was unfinished).

I've found very simple steps to reproduce suspend failure on am335x-evm (should also work on BBB) - do below sequence with USB device plugged:

echo platform > /sys/power/pm_test
echo 1 > /sys/power/pm_print_times
[ echo 0 > /sys/module/printk/parameters/console_suspend ] echo mem > /sys/power/state

[   95.499685] calling  47400000.usb+ @ 733, parent: ocp
[   95.504818] am335x-usb-childs 47400000.usb: runtime PM trying to suspend device but active child
[   95.513750] am335x-usb-childs 47400000.usb: omap device suspend failure 0

Below I've attached possible patch which converts OMAP device to use pm_runtime_force_suspend/resume().

Quoted 14 lines · Grygorii Strashko

My personal thought here is that removing of pm_runtime_set_active() will not fix root cause of the problem, but rather hide it :( and, probably, real fix will be to update USB framework to ensure that all suspend devices are also PM runtime suspend (not sure how) or add few more pm_suspend_ignore_children() calls
(for example as I've tried to do in [2], but this was unfinished).

I've found very simple steps to reproduce suspend failure on am335x-evm (should also work on BBB) - do below sequence with USB device plugged:

echo platform > /sys/power/pm_test
echo 1 > /sys/power/pm_print_times
[ echo 0 > /sys/module/printk/parameters/console_suspend ] echo mem > /sys/power/state

Quoted 6 lines

[   95.499685] calling  47400000.usb+ @ 733, parent: ocp
[   95.504818] am335x-usb-childs 47400000.usb: runtime PM trying to suspend device but active child
[   95.513750] am335x-usb-childs 47400000.usb: omap device suspend failure 0

Below I've attached possible patch which converts OMAP device to use pm_runtime_force_suspend/resume().

It seems to almost work for my PM test cases.. It seems that serial console somehow won't get restored after suspend/resume cycle on omap3 though.

The system enters off mode during suspend, and wakes up properly so I can ssh to it after resume. But the serial console no longer works after resume. This is with 8250-omap driver.

Quoted 22 lines · Tony Lindgren

Quoted 20 lines · Grygorii Strashko

My personal thought here is that removing of pm_runtime_set_active() will not fix root cause of the problem, but rather hide it :( and, probably, real fix will be to update USB framework to ensure that all suspend devices are also PM runtime suspend (not sure how) or add few more pm_suspend_ignore_children() calls
(for example as I've tried to do in [2], but this was unfinished).

I've found very simple steps to reproduce suspend failure on am335x-evm (should also work on BBB) - do below sequence with USB device plugged:

echo platform > /sys/power/pm_test
echo 1 > /sys/power/pm_print_times
[ echo 0 > /sys/module/printk/parameters/console_suspend ] echo mem > /sys/power/state

[   95.499685] calling  47400000.usb+ @ 733, parent: ocp
[   95.504818] am335x-usb-childs 47400000.usb: runtime PM trying to suspend device but active child
[   95.513750] am335x-usb-childs 47400000.usb: omap device suspend failure 0

Below I've attached possible patch which converts OMAP device to use pm_runtime_force_suspend/resume().

Quoted 6 lines

It seems to almost work for my PM test cases.. It seems that serial console somehow won't get restored after suspend/resume cycle on omap3 though.

The system enters off mode during suspend, and wakes up properly so I can ssh to it after resume. But the serial console no longer works after resume. This is with 8250-omap driver.

And FYI, on omap4 this produces a bunch of L3 irq errors on suspend.

Quoted 26 lines · Johan Hovold

Since commit a8636c89648a ("PM / Runtime: Don't allow to suspend a device with an active child"), which went into 4.10, it is no longer permitted to set RPM_SUSPENDED state for a device with active children (unless power.ignore_children is set).

This specifically means that the attempts to do just that from the omap pm-domain suspend_noirq callback have since been failing whenever a child is active, for example:

am335x-usb-childs 47400000.usb: runtime PM trying to suspend
device but active child

Silence this warning by dropping the broken pm_runtime_set_suspended() call from the omap suspend_noirq callback along with the redundant pm_runtime_set_active() in resume_noirq.

This effectively reverts commit 3522bf7bfa24 ("ARM: OMAP2+: omap_device:
maintain sane runtime pm status around suspend/resume"), which started updating the RPM state after the runtime_suspend callback (!) for active omap devices had been called during system suspend. The rationale was that a later pm_runtime_get_sync() would then fail (even after runtime pm had been disabled) and that this in turn would avoid any external aborts when accessing registers with clocks disabled. (See also commit 6f3c77b040fc ("PM / Runtime: let rpm_resume() succeed if RPM_ACTIVE, even when disabled, v2").

Quoted 7 lines

But during the suspend_noirq phase all children would already have been suspended and their drivers would specifically not attempt any further register accesses. And if this was all just a workaround for random device drivers doing cross-tree calls during system suspend, those drivers should be fixed and updated to explicitly model such dependencies using device-links instead (and either way, any such calls have been causing crashes since 4.10).

I'd like to provide some background and comments here.

1) OMAP platform is PM runtime centric - in other words all device's PM operations (power on/off) are done through PM runtime calls and devices drivers do not really change device's Power states during suspend/resume - just do preparation for suspend. The final disabling of devices is done form _od_suspend_noirq() or if device driver calls pm_runtime_force_suspend() directly during suspend.

2) Initially all this suspend_noirq code was introduced due to commit

commit 1e2ef05bb8cf851a694d38e9170c89e7ff052741

Author: Rafael J. Wysocki <[email protected]>
Date:   Wed Jul 6 10:51:58 2011 +0200

PM: Limit race conditions between runtime PM and system sleep (v2)

which blocks PM runtime during suspend resume. And, at that time, there were no pm_runtime_force_suspend/resume() neither proper support for power domains.

As result, below two calls really switch OFF device and its state should be RPM_SUSPENDED as it will reflect real PM state of HW:

	m_generic_runtime_suspend(dev)
	omap_device_idle(pdev);

In general, now the code in _od_resume/resume_noirq() callback is equivalent to pm_runtime_force_suspend/resume().

3) It's expected to ignore -EBUSY return code from pm_generic_runtime_suspend(dev) in _od_suspend_noirq(), as such code (-EBUSY) tells OMAP device framework that device should be kept active during suspend (for example serial device in case of "no_console_suspend").

commit 4b7ec5accecdb136c7afaf8739a06d5335cc05aa

Author: Sourav Poddar <[email protected]>
Date:   Sat Apr 27 01:55:34 2013 +0530

arm: omap2+: omap_device: remove no_idle_on_suspend

As result, when "runtime PM trying to suspend device but active child" happens the OMAP device framework will ignore it and gracefully continue to suspend where target device will finally powered off (depending on suspend mode and device). On resume, target device will not be powered on, because its state was not marked as OMAP_DEVICE_SUSPENDED, so further attempts to power on device with pm_runtime_get_sync() will be a NOP (because device state is RPM_ACTIVE) and any access to the device will fail (system crash).

4) Unfortunately, commit a8636c89648a ("PM / Runtime: Don't allow to suspend a device with an active child") "breaks" OMAP suspend functionality (or makes visible more fundamental issues of PM runtime vs Sys suspend), because not all Kernel subsystem (especially USB) maintain their devices PM runtime state properly during suspend, which cause pm_runtime_set_suspended() (or pm_runtime_force_suspend()) to return -EBUSY and, as result, misbehave of OMAP device framework.

My personal thought here is that removing of pm_runtime_set_active() will not fix root cause of the problem, but rather hide it :( and, probably, real fix will be to update USB framework to ensure that all suspend devices are also PM runtime suspend (not sure how) or add few more pm_suspend_ignore_children() calls (for example as I've tried to do in [2], but this was unfinished).

I've found very simple steps to reproduce suspend failure on am335x-evm (should also > work on BBB) - do below sequence with USB device plugged:

echo platform > /sys/power/pm_test
echo 1 > /sys/power/pm_print_times
[ echo 0 > /sys/module/printk/parameters/console_suspend ] echo mem > /sys/power/state

[   95.499685] calling  47400000.usb+ @ 733, parent: ocp
[   95.504818] am335x-usb-childs 47400000.usb: runtime PM trying to suspend device but active child
[   95.513750] am335x-usb-childs 47400000.usb: omap device suspend failure 0

Below I've attached possible patch which converts OMAP device to use pm_runtime_force_suspend/resume().

Quoted 56 lines · Grygorii Strashko

Quoted 26 lines · Johan Hovold

Since commit a8636c89648a ("PM / Runtime: Don't allow to suspend a device with an active child"), which went into 4.10, it is no longer permitted to set RPM_SUSPENDED state for a device with active children (unless power.ignore_children is set).

This specifically means that the attempts to do just that from the omap pm-domain suspend_noirq callback have since been failing whenever a child is active, for example:

am335x-usb-childs 47400000.usb: runtime PM trying to suspend
device but active child

Silence this warning by dropping the broken pm_runtime_set_suspended() call from the omap suspend_noirq callback along with the redundant pm_runtime_set_active() in resume_noirq.

This effectively reverts commit 3522bf7bfa24 ("ARM: OMAP2+: omap_device:
maintain sane runtime pm status around suspend/resume"), which started updating the RPM state after the runtime_suspend callback (!) for active omap devices had been called during system suspend. The rationale was that a later pm_runtime_get_sync() would then fail (even after runtime pm had been disabled) and that this in turn would avoid any external aborts when accessing registers with clocks disabled. (See also commit 6f3c77b040fc ("PM / Runtime: let rpm_resume() succeed if RPM_ACTIVE, even when disabled, v2").

Quoted 7 lines

But during the suspend_noirq phase all children would already have been suspended and their drivers would specifically not attempt any further register accesses. And if this was all just a workaround for random device drivers doing cross-tree calls during system suspend, those drivers should be fixed and updated to explicitly model such dependencies using device-links instead (and either way, any such calls have been causing crashes since 4.10).

I'd like to provide some background and comments here.

1) OMAP platform is PM runtime centric - in other words all device's PM operations (power on/off) are done through PM runtime calls and devices drivers do not really change device's Power states during suspend/resume - just do preparation for suspend. The final disabling of devices is done form _od_suspend_noirq() or if device driver calls pm_runtime_force_suspend() directly during suspend.

2) Initially all this suspend_noirq code was introduced due to commit

commit 1e2ef05bb8cf851a694d38e9170c89e7ff052741

Author: Rafael J. Wysocki <[email protected]>
Date:   Wed Jul 6 10:51:58 2011 +0200

PM: Limit race conditions between runtime PM and system sleep (v2)

which blocks PM runtime during suspend resume. And, at that time, there were no pm_runtime_force_suspend/resume() neither proper support for power domains.

Quoted 4 lines

As result, below two calls really switch OFF device and its state should be RPM_SUSPENDED as it will reflect real PM state of HW:

	m_generic_runtime_suspend(dev)
	omap_device_idle(pdev);

That's the point to be discussed; does the runtime status really need to reflect the hardware state *during* suspend?

As you've noticed, not all subsystems enforce that, even if omap seems to have been expecting it.

And as I mentioned in the commit message, at least the point about wanting to have late pm_runtime_get_sync() fail during suspend appears to be moot.

Quoted 16 lines

In general, now the code in _od_resume/resume_noirq() callback is equivalent to pm_runtime_force_suspend/resume().

3) It's expected to ignore -EBUSY return code from pm_generic_runtime_suspend(dev) in _od_suspend_noirq(), as such code (-EBUSY) tells OMAP device framework that device should be kept active during suspend (for example serial device in case of "no_console_suspend").

commit 4b7ec5accecdb136c7afaf8739a06d5335cc05aa

Author: Sourav Poddar <[email protected]>
Date:   Sat Apr 27 01:55:34 2013 +0530

arm: omap2+: omap_device: remove no_idle_on_suspend

Quoted 8 lines

As result, when "runtime PM trying to suspend device but active child" happens the OMAP device framework will ignore it and gracefully continue to suspend where target device will finally powered off (depending on suspend mode and device). On resume, target device will not be powered on, because its state was not marked as OMAP_DEVICE_SUSPENDED, so further attempts to power on device with pm_runtime_get_sync() will be a NOP (because device state is RPM_ACTIVE) and any access to the device will fail (system crash).

I believe you're mistaken here; _od_suspend_noirq() will continue to power-off *and* set OMAP_DEVICE_SUSPENDED, so that device is again powered during resume_noirq also after this patch has been applied.

Specifically, note that the return value of pm_runtime_set_suspended() was never checked, so the only difference here would be that the error message is suppressed.

Quoted 8 lines

4) Unfortunately, commit a8636c89648a ("PM / Runtime: Don't allow to suspend a device with an active child") "breaks" OMAP suspend functionality (or makes visible more fundamental issues of PM runtime vs Sys suspend), because not all Kernel subsystem (especially USB) maintain their devices PM runtime state properly during suspend, which cause pm_runtime_set_suspended() (or pm_runtime_force_suspend()) to return -EBUSY and, as result, misbehave of OMAP device framework.

Again, the return value of pm_runtime_set_suspended() was never checked so the only thing commit a8636c89648a ("PM / Runtime: Don't allow to suspend a device with an active child") did was to trigger those error messages and leave the runtime PM state at RPM_ACTIVE. The latter does not seems to have any other side effects, and specifically, the device would still be powered off.

Quoted 17 lines

My personal thought here is that removing of pm_runtime_set_active() will not fix root cause of the problem, but rather hide it :( and, probably, real fix will be to update USB framework to ensure that all suspend devices are also PM runtime suspend (not sure how) or add few more pm_suspend_ignore_children() calls (for example as I've tried to do in [2], but this was unfinished).

I've found very simple steps to reproduce suspend failure on am335x-evm (should also > work on BBB) - do below sequence with USB device plugged:

echo platform > /sys/power/pm_test
echo 1 > /sys/power/pm_print_times
[ echo 0 > /sys/module/printk/parameters/console_suspend ] echo mem > /sys/power/state

Quoted 6 lines

[   95.499685] calling  47400000.usb+ @ 733, parent: ocp
[   95.504818] am335x-usb-childs 47400000.usb: runtime PM trying to suspend device but active child
[   95.513750] am335x-usb-childs 47400000.usb: omap device suspend failure 0

Below I've attached possible patch which converts OMAP device to use pm_runtime_force_suspend/resume().

What code are you running above? The OMAP PM code should not be failing due to that error message at least (as mentioned twice above).

I have musb suspend working on BBB with the patch I posted yesterday which keeps the controller at RPM_ACTIVE during suspend:

	https://marc.info/?i=20170724094939.21477-1-johan%40kernel.org

Hi Johan,

Quoted 38 lines · Johan Hovold

Quoted 36 lines · Grygorii Strashko

Quoted 26 lines · Johan Hovold

Since commit a8636c89648a ("PM / Runtime: Don't allow to suspend a device with an active child"), which went into 4.10, it is no longer permitted to set RPM_SUSPENDED state for a device with active children (unless power.ignore_children is set).

This specifically means that the attempts to do just that from the omap pm-domain suspend_noirq callback have since been failing whenever a child is active, for example:

am335x-usb-childs 47400000.usb: runtime PM trying to suspend
device but active child

Silence this warning by dropping the broken pm_runtime_set_suspended() call from the omap suspend_noirq callback along with the redundant pm_runtime_set_active() in resume_noirq.

This effectively reverts commit 3522bf7bfa24 ("ARM: OMAP2+: omap_device:
maintain sane runtime pm status around suspend/resume"), which started updating the RPM state after the runtime_suspend callback (!) for active omap devices had been called during system suspend. The rationale was that a later pm_runtime_get_sync() would then fail (even after runtime pm had been disabled) and that this in turn would avoid any external aborts when accessing registers with clocks disabled. (See also commit 6f3c77b040fc ("PM / Runtime: let rpm_resume() succeed if RPM_ACTIVE, even when disabled, v2").

Quoted 7 lines

But during the suspend_noirq phase all children would already have been suspended and their drivers would specifically not attempt any further register accesses. And if this was all just a workaround for random device drivers doing cross-tree calls during system suspend, those drivers should be fixed and updated to explicitly model such dependencies using device-links instead (and either way, any such calls have been causing crashes since 4.10).

I'd like to provide some background and comments here.

Quoted 7 lines

Quoted 4 lines

As result, below two calls really switch OFF device and its state should be RPM_SUSPENDED as it will reflect real PM state of HW:

	m_generic_runtime_suspend(dev)
	omap_device_idle(pdev);

That's the point to be discussed; does the runtime status really need to reflect the hardware state *during* suspend?

At least there are no restriction, as I know.

Quoted 2 lines

As you've noticed, not all subsystems enforce that, even if omap seems to have been expecting it.

True.

Quoted 3 lines

And as I mentioned in the commit message, at least the point about wanting to have late pm_runtime_get_sync() fail during suspend appears to be moot.

Correct. It was introduced long time ago (before device-links).

Quoted 13 lines

Quoted 8 lines

As result, when "runtime PM trying to suspend device but active child" happens the OMAP device framework will ignore it and gracefully continue to suspend where target device will finally powered off (depending on suspend mode and device). On resume, target device will not be powered on, because its state was not marked as OMAP_DEVICE_SUSPENDED, so further attempts to power on device with pm_runtime_get_sync() will be a NOP (because device state is RPM_ACTIVE) and any access to the device will fail (system crash).

I believe you're mistaken here; _od_suspend_noirq() will continue to power-off *and* set OMAP_DEVICE_SUSPENDED, so that device is again powered during resume_noirq also after this patch has been applied.

Quoted 3 lines

Specifically, note that the return value of pm_runtime_set_suspended() was never checked, so the only difference here would be that the error message is suppressed.

Correct. Sorry. My bad - it was Monday.

Quoted 29 lines

Quoted 16 lines

My personal thought here is that removing of pm_runtime_set_active() will not fix root cause of the problem, but rather hide it :( and, probably, real fix will be to update USB framework to ensure that all suspend devices are also PM runtime suspend (not sure how) or add few more pm_suspend_ignore_children() calls (for example as I've tried to do in [2], but this was unfinished).

I've found very simple steps to reproduce suspend failure on am335x-evm (should also > work on BBB) - do below sequence with USB device plugged:

echo platform > /sys/power/pm_test
echo 1 > /sys/power/pm_print_times
[ echo 0 > /sys/module/printk/parameters/console_suspend ] echo mem > /sys/power/state

Quoted 6 lines

[   95.499685] calling  47400000.usb+ @ 733, parent: ocp
[   95.504818] am335x-usb-childs 47400000.usb: runtime PM trying to suspend device but active child
[   95.513750] am335x-usb-childs 47400000.usb: omap device suspend failure 0

Below I've attached possible patch which converts OMAP device to use pm_runtime_force_suspend/resume().

What code are you running above? The OMAP PM code should not be failing due to that error message at least (as mentioned twice above).

I have musb suspend working on BBB with the patch I posted yesterday which keeps the controller at RPM_ACTIVE during suspend:

Quoted 1 line

	https://marc.info/?i=20170724094939.21477-1-johan%40kernel.org

I re-checked it on clean master (Linux 4.13-rc2) with and without your patches and see no issues, just "runtime PM trying to suspend device but active child" message is gone. Above test sequence still can be used without any additional patches.

So, thank you for your patches and sorry for the noise.

Tested-by Grygorii Strashko <[email protected]>

Quoted 3 lines · Grygorii Strashko

So, thank you for your patches and sorry for the noise.

Tested-by Grygorii Strashko <[email protected]>

Thanks for testing.

Quoted 6 lines · Grygorii Strashko

Quoted 3 lines

So, thank you for your patches and sorry for the noise.

Tested-by Grygorii Strashko <[email protected]>

Thanks for testing.

So does the patch description need updating?

And this is needed as a fix for the -rc cycle in addition to your musb patch?

On Wed, Jul 26, 2017 at 01:17:17AM -0700, Tony Lindgren wrote: > * Johan Hovold <[email protected]> [170726 00:51]:

Quoted 8 lines

Quoted 6 lines · Grygorii Strashko

Quoted 3 lines

So, thank you for your patches and sorry for the noise.

Tested-by Grygorii Strashko <[email protected]>

Thanks for testing.

So does the patch description need updating?

I don't think so.

I did notice that I left out a "would" in the final sentence

	"and either way, any such calls *would* have been causing
	crashes since 4.10"

which perhaps you could add when applying?

Quoted 2 lines

And this is needed as a fix for the -rc cycle in addition to your musb patch?

Unlike the musb patch, this one is not critical and could possibly wait for 4.14. But since all it does is to get rid of a (since 4.10) broken state update, and thereby those warning messages on suspend, I'd say it's -rc material.

Since commit a8636c89648a ("PM / Runtime: Don't allow to suspend a device with an active child"), which went into 4.10, it is no longer permitted to set RPM_SUSPENDED state for a device with active children (unless power.ignore_children is set).

This specifically means that the attempts to do just that from the omap pm-domain suspend_noirq callback have since been failing whenever a child is active, for example:

am335x-usb-childs 47400000.usb: runtime PM trying to suspend
device but active child

Silence this warning by dropping the broken pm_runtime_set_suspended() call from the omap suspend_noirq callback along with the redundant pm_runtime_set_active() in resume_noirq.