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

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Message-ID: <CAJZ5v0jc-tjs_a+RCzu6bvrbfhv5QHqsWx-zKjH0wpisiJciKA@mail.gmail.com>
Date: Thu, 3 Jul 2025 16:29:46 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Mario Limonciello <superm1@...nel.org>
Cc: "Rafael J . Wysocki" <rafael@...nel.org>, Alex Deucher <alexander.deucher@....com>, 
	Bjorn Helgaas <bhelgaas@...gle.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 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.

It also requires more work/review from other people.

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!

> 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
>