Re: [PATCH] PCI: Fix the ACPI power state during runtime resume

Abhishek Sahu
2022-04-06T20:23:24Z

On 4/6/2022 5:36 PM, Rafael J. Wysocki wrote:
> On Wednesday, April 6, 2022 7:32:45 AM CEST Abhishek Sahu wrote:
>> On 4/5/2022 10:20 PM, Rafael J. Wysocki wrote:
>>> On Tuesday, April 5, 2022 6:36:34 PM CEST Abhishek Sahu wrote:
>>>> On 2/8/2022 4:00 PM, Abhishek Sahu wrote:
>>>>> On 2/8/2022 12:28 AM, Rafael J. Wysocki wrote:
>>>>>> On Saturday, February 5, 2022 12:32:19 AM CET Bjorn Helgaas wrote:
>>>>>>> [+cc Rafael, hoping for your review :)
>>>>>>
>>>>>> +Mika
>>>>>>
>>>>>>> Wonder if we should add something like this to MAINTAINERS so you get
>>>>>>> cc'd on power-related things:
>>>>>>>
>>>>>>> diff --git a/MAINTAINERS b/MAINTAINERS
>>>>>>> index ea3e6c914384..3d9a211cad5d 100644
>>>>>>> --- a/MAINTAINERS
>>>>>>> +++ b/MAINTAINERS
>>>>>>> @@ -15422,6 +15422,7 @@ F: include/linux/pm.h
>>>>>>> F: include/linux/pm_*
>>>>>>> F: include/linux/powercap.h
>>>>>>> F: kernel/configs/nopm.config
>>>>>>> +K: pci_[a-z_]*power[a-z_]*\(
>>>>>>
>>>>>> It seems so, but generally PM patches should be CCed to linux-pm anyway.
>>>>>>
>>>>>>>
>>>>>>> DYNAMIC THERMAL POWER MANAGEMENT (DTPM)
>>>>>>> M: Daniel Lezcano <daniel.lezcano@kernel.org>
>>>>>>> ]
>>>>>>>
>>>>>>> On Mon, Jan 24, 2022 at 05:51:07PM +0530, Abhishek Sahu wrote:
>>>>>>>> Consider the following sequence during PCI device runtime
>>>>>>>> suspend/resume:
>>>>>>>>
>>>>>>>> 1. PCI device goes into runtime suspended state. The PCI state
>>>>>>>> will be changed to PCI_D0 and then pci_platform_power_transition()
>>>>>>>> will be called which changes the ACPI state to ACPI_STATE_D3_HOT.
>>>>>>
>>>>>> You mean PCI_D3hot I suppose?
>>>>>>
>>>>>
>>>>> Yes. It should be PCI_D3hot here.
>>>>>
>>>>>>>> 2. Parent bridge goes into runtime suspended state. If parent
>>>>>>>> bridge supports D3cold, then it will change the power state of all its
>>>>>>>> children to D3cold state and the power will be removed.
>>>>>>>>
>>>>>>>> 3. During wake-up time, the bridge will be runtime resumed first
>>>>>>>> and pci_power_up() will be called for the bridge. Now, the power
>>>>>>>> supply will be resumed.
>>>>>>>>
>>>>>>>> 4. pci_resume_bus() will be called which will internally invoke
>>>>>>>> pci_restore_standard_config(). pci_update_current_state()
>>>>>>>> will read PCI_PM_CTRL register and the current_state will be
>>>>>>>> updated to D0.
>>>>>>>>
>>>>>>>> In the above process, at step 4, the ACPI device state will still be
>>>>>>>> ACPI_STATE_D3_HOT since pci_platform_power_transition() is not being
>>>>>>>> invoked.
>>>>>>
>>>>>> I'm not quite following.
>>>>>>
>>>>>> I'm assuming that this description applies to the endpoint device that was
>>>>>> previously put into D3_hot.
>>>>>>
>>>>>
>>>>> Yes. This is applicable for endpoint devices which was previously put
>>>>> into D3hot.
>>>>>
>>>>>> Since its current state is D3_hot, it is not D0 (in particular) and the
>>>>>> pci_set_power_state() in pci_restore_standard_config() should put int into
>>>>>> D0 proper, including the platform firmware part.
>>>>>>
>>>>>
>>>>> The pci_restore_standard_config() for endpoint devices are being called
>>>>> internally during wake-up of upstream bridge.
>>>>>
>>>>> pci_power_up(struct pci_dev *dev)
>>>>> {
>>>>> ...
>>>>> if (dev->runtime_d3cold) {
>>>>> /*
>>>>> * When powering on a bridge from D3cold, the whole hierarchy
>>>>> * may be powered on into D0uninitialized state, resume them to
>>>>> * give them a chance to suspend again
>>>>> */
>>>>> pci_resume_bus(dev->subordinate);
>>>>> }
>>>>> ...
>>>>> }
>>>>>
>>>>> For the upstream bridge, the above code will trigger the wake-up of
>>>>> endpoint devices and then following code will be executed for the
>>>>> endpoint devices:
>>>>>
>>>>> pci_update_current_state(struct pci_dev *dev, pci_power_t state)
>>>>> {
>>>>> if (platform_pci_get_power_state(dev) == PCI_D3cold ||
>>>>> !pci_device_is_present(dev)) {
>>>>> dev->current_state = PCI_D3cold;
>>>>> } else if (dev->pm_cap) {
>>>>> u16 pmcsr;
>>>>>
>>>>> pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr);
>>>>> dev->current_state = (pmcsr & PCI_PM_CTRL_STATE_MASK);
>>>>> } else {
>>>>> dev->current_state = state;
>>>>> }
>>>>> }
>>>>>
>>>>> In the above code, the current_state will be set to D0 for the
>>>>> endpoint devices since it will go into second block where
>>>>> it will read the PM_CTRL register.
>>>>>
>>>>>>>> We need call the pci_platform_power_transition() with state
>>>>>>>> D0 to change the ACPI state to ACPI_STATE_D0.
>>>>>>>>
>>>>>>>> This patch calls pci_power_up() if current power state is D0 inside
>>>>>>>> pci_restore_standard_config(). This pci_power_up() will change the
>>>>>>>> ACPI state to ACPI_STATE_D0.
>>>>>>>>
>>>>>>>> Following are the steps to confirm:
>>>>>>>>
>>>>>>>> Enable the debug prints in acpi_pci_set_power_state()
>>>>>>>>
>>>>>>>> 0000:01:00.0 is PCI device and 0000:00:01.0 is parent bridge device
>>>>>>>>
>>>>>>>> Before:
>>>>>>>>
>>>>>>>> 0000:01:00.0: power state changed by ACPI to D3hot
>>>>>>>> 0000:00:01.0: power state changed by ACPI to D3cold
>>>>>>>> 0000:00:01.0: power state changed by ACPI to D0
>>>>>>>>
>>>>>>>> After:
>>>>>>>>
>>>>>>>> 0000:01:00.0: power state changed by ACPI to D3hot
>>>>>>>> 0000:00:01.0: power state changed by ACPI to D3cold
>>>>>>>> 0000:00:01.0: power state changed by ACPI to D0
>>>>>>>> 0000:01:00.0: power state changed by ACPI to D0
>>>>>>>>
>>>>>>>> So with this patch, the PCI device ACPI state is also being
>>>>>>>> changed to D0.
>>>>>>>>
>>>>>>>> Signed-off-by: Abhishek Sahu <abhsahu@nvidia.com>
>>>>>>>> ---
>>>>>>>> drivers/pci/pci-driver.c | 14 +++++++++++---
>>>>>>>> 1 file changed, 11 insertions(+), 3 deletions(-)
>>>>>>>>
>>>>>>>> diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
>>>>>>>> index 588588cfda48..64e0cca12f16 100644
>>>>>>>> --- a/drivers/pci/pci-driver.c
>>>>>>>> +++ b/drivers/pci/pci-driver.c
>>>>>>>> @@ -521,14 +521,22 @@ static void pci_device_shutdown(struct device *dev)
>>>>>>>> */
>>>>>>>> static int pci_restore_standard_config(struct pci_dev *pci_dev)
>>>>>>>> {
>>>>>>>> + int error = 0;
>>>>>>>> pci_update_current_state(pci_dev, PCI_UNKNOWN);
>>>>>>>>
>>>>>>>> if (pci_dev->current_state != PCI_D0) {
>>>>>>>> - int error = pci_set_power_state(pci_dev, PCI_D0);
>>>>>>>> - if (error)
>>>>>>>> - return error;
>>>>>>>> + error = pci_set_power_state(pci_dev, PCI_D0);
>>>>>>>> + } else {
>>>>>>>> + /*
>>>>>>>> + * The platform power state can still be non-D0, so this is
>>>>>>>> + * required to change the platform power state to D0.
>>>>>>>> + */
>>>>>>
>>>>>> This really isn't expected to happen.
>>>>>>
>>>>>> If the device's power state has been changed to D3hot by ACPI, it is not in D0.
>>>>>>
>>>>>> It looks like the state tracking is not working here.
>>>>>>
>>>>>
>>>>> The state setting to D0 is happening due to the current logic present in
>>>>> pci_update_current_state(). If we can fix the logic in
>>>>> pci_update_current_state() to detect this condition and return state D3hot,
>>>>> then it should also fix the issue.
>>>>>
>>>>> Thanks,
>>>>> Abhishek
>>>>>
>>>>
>>>> Hi Rafael/Mika,
>>>>
>>>> Could you please help regarding the correct way to fix this issue.
>>>> I can update the patch accordingly.
>>>
>>> I think you can try one of the patches posted recently:
>>>
>>> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatchwork.kernel.org%2Fproject%2Flinux-pm%2Fpatch%2F3623886.MHq7AAxBmi%40kreacher%2F&amp;data=04%7C01%7Cabhsahu%40nvidia.com%7C87470c4f30f14871bcc708da17c5e913%7C43083d15727340c1b7db39efd9ccc17a%7C0%7C0%7C637848436478123578%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=USJs87Fmm0Vcjm1YWszZCBTpcNQED3InOuOdGgE3f88%3D&amp;reserved=0
>>>
>>> Thanks!
>>>
>>>
>>>
>>
>> Thanks Rafael.
>> I have applied both the changes and still the issue which I mentioned is happening.
>>
>> Following are the prints:
>>
>> 0000:01:00.0: power state changed by ACPI to D3hot
>> 0000:00:01.0: power state changed by ACPI to D3cold
>> 0000:00:01.0: power state changed by ACPI to D0
>>
>> So ACPI state change is still not happening for PCI endpoint devices.
>>
>> Also, the I checked the code and the pci_power_up() will not be called
>> for endpoint devices. For endpoints, pci_restore_standard_config() will
>> be called first where the current state will come as D0.
>
> OK, I see.
>
> The problem is that if the PCI device goes to D0 because of the bridge power-up,
> it's ACPI companion's power state may not follow, which means that we really
> want to do a full power-up in there.
>
> Please test the appended patch with the patch from
>
> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatchwork.kernel.org%2Fproject%2Flinux-pm%2Fpatch%2F3623886.MHq7AAxBmi%40kreacher%2F&amp;data=04%7C01%7Cabhsahu%40nvidia.com%7C87470c4f30f14871bcc708da17c5e913%7C43083d15727340c1b7db39efd9ccc17a%7C0%7C0%7C637848436478123578%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&amp;sdata=USJs87Fmm0Vcjm1YWszZCBTpcNQED3InOuOdGgE3f88%3D&amp;reserved=0
>
> still applied.
>
> ---
> drivers/pci/pci-driver.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> Index: linux-pm/drivers/pci/pci-driver.c
> ===================================================================
> --- linux-pm.orig/drivers/pci/pci-driver.c
> +++ linux-pm/drivers/pci/pci-driver.c
> @@ -1312,7 +1312,7 @@ static int pci_pm_runtime_resume(struct
> * to a driver because although we left it in D0, it may have gone to
> * D3cold when the bridge above it runtime suspended.
> */
> - pci_restore_standard_config(pci_dev);
> + pci_pm_default_resume_early(pci_dev);
>
> if (!pci_dev->driver)
> return 0;
>

Thanks Rafael.
With the above code change, the issue is getting fixed and the
PCI endpoint power state is also changing to D0.

0000:01:00.0: power state changed by ACPI to D3hot
0000:00:01.0: power state changed by ACPI to D3cold
0000:00:01.0: power state changed by ACPI to D0
0000:01:00.0: power state changed by ACPI to D0

Regards,
Abhishek