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

Rafael J. Wysocki
2022-04-06T20:27:16Z

On Wednesday, April 6, 2022 8:43:19 PM CEST Abhishek Sahu wrote:
> 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

Thanks for testing!