linux-kernel - Re: [PATCH v4 0/5] Improvements to S5 power consumption

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Message-ID: <8fda8cf1-1291-422e-bb63-094e38c47b7b@kernel.org>
Date: Thu, 3 Jul 2025 22:01:30 -0400
From: Mario Limonciello <superm1@...nel.org>
To: "Rafael J. Wysocki" <rafael@...nel.org>,
 Bjorn Helgaas <bhelgaas@...gle.com>
Cc: Alex Deucher <alexander.deucher@....com>,
 "open list:RADEON and AMDGPU DRM DRIVERS" <amd-gfx@...ts.freedesktop.org>,
 "open list:HIBERNATION (aka Software Suspend, aka swsusp)"
 <linux-pm@...r.kernel.org>,
 "open list:PCI SUBSYSTEM" <linux-pci@...r.kernel.org>,
 open list <linux-kernel@...r.kernel.org>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Danilo Krummrich <dakr@...nel.org>,
 "James E . J . Bottomley" <James.Bottomley@...senpartnership.com>,
 "Martin K . Petersen" <martin.petersen@...cle.com>,
 "open list:DRM DRIVERS" <dri-devel@...ts.freedesktop.org>,
 "open list:SCSI SUBSYSTEM" <linux-scsi@...r.kernel.org>,
 "open list:USB SUBSYSTEM" <linux-usb@...r.kernel.org>,
 Mario Limonciello <mario.limonciello@....com>
Subject: Re: [PATCH v4 0/5] Improvements to S5 power consumption

On 7/3/25 10:29, Rafael J. Wysocki wrote:
> On Mon, Jun 16, 2025 at 7:50 PM Mario Limonciello <superm1@...nel.org> wrote:
>>
>> From: Mario Limonciello <mario.limonciello@....com>
>>
>> A variety of issues both in function and in power consumption have been
>> raised as a result of devices not being put into a low power state when
>> the system is powered off.
>>
>> There have been some localized changes[1] to PCI core to help these issues,
>> but they have had various downsides.
>>
>> This series instead tries to use the S4 flow when the system is being
>> powered off.  This lines up the behavior with what other operating systems
>> do as well.  If for some reason that fails or is not supported, unwind and
>> do the previous S5 flow that will wake all devices and run their shutdown()
>> callbacks.
> 
> I actually like this approach, but I think that it is risky.

Yeah; it does touch a lot of areas.

> 
> It also requires more work/review from other people.

I view patches 3-5 as being dependent upon patch 1, so until we have 
agreement on that one the others might not make a lot of sense.

Bjorn,

Can you take a look at patch 2?

> 
> I'll be sending some comments on the individual patches going forward,
> but I think the earliest it can go in is after 6.17-rc1 (given it is
> reviewed properly till then).

Thanks!

> 
> Thanks!
> 
>> v3->v4:
>>   * Fix LKP robot failure
>>   * Rebase on v6.16-rc2
>>
>> Previous submissions [1]:
>> Link: https://lore.kernel.org/linux-pm/CAJZ5v0hrKEJa8Ad7iiAvQ3d_0ysVhzZcXSYc5kkL=6vtseF+bg@mail.gmail.com/T/#m91e4eae868a7405ae579e89b135085f4906225d2
>> Link: https://lore.kernel.org/linux-pci/20250506041934.1409302-1-superm1@kernel.org/
>> Link: https://lore.kernel.org/linux-pci/20231213182656.6165-1-mario.limonciello@amd.com/ (v1)
>> Link: https://lore.kernel.org/linux-pm/20250514193406.3998101-1-superm1@kernel.org/ (v2)
>> Link: https://lore.kernel.org/linux-pm/20250609024619.407257-1-superm1@kernel.org/ (v3)
>>
>> Mario Limonciello (5):
>>    PM: Use hibernate flows for system power off
>>    PCI: Put PCIe ports with downstream devices into D3 at hibernate
>>    drm/amd: Avoid evicting resources at S5
>>    scsi: Add PM_EVENT_POWEROFF into suspend callbacks
>>    usb: sl811-hcd: Add PM_EVENT_POWEROFF into suspend callbacks
>>
>>   drivers/base/power/main.c                  |  7 ++
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_device.c |  4 +
>>   drivers/pci/pci-driver.c                   | 94 ++++++++++++++--------
>>   drivers/scsi/mesh.c                        |  1 +
>>   drivers/scsi/stex.c                        |  1 +
>>   drivers/usb/host/sl811-hcd.c               |  1 +
>>   include/linux/pm.h                         |  3 +
>>   include/trace/events/power.h               |  3 +-
>>   kernel/reboot.c                            |  6 ++
>>   9 files changed, 86 insertions(+), 34 deletions(-)
>>
>> --
>> 2.43.0
>>