[PATCH] drm/amd: Allow s0ix without BIOS support

[Limonciello, Mario]

[AMD Official Use Only - General]



> -----Original Message-----
> From: Alex Deucher <alexdeucher at gmail.com>
> Sent: Wednesday, February 1, 2023 21:49
> To: Limonciello, Mario <Mario.Limonciello at amd.com>
> Cc: amd-gfx at lists.freedesktop.org; Rafael Ávila de Espíndola
> <rafael at espindo.la>
> Subject: Re: [PATCH] drm/amd: Allow s0ix without BIOS support
> 
> On Wed, Jan 25, 2023 at 1:33 PM Mario Limonciello
> <mario.limonciello at amd.com> wrote:
> >
> > We guard the suspend entry code from running unless we have proper
> > BIOS support for either S3 mode or s0ix mode.
> >
> > If a user's system doesn't support either of these modes the kernel
> > still does offer s2idle in `/sys/power/mem_sleep` so there is an
> > expectation from users that it works even if the power consumption
> > remains very high.
> >
> > Rafael Ávila de Espíndola reports that a system of his has a
> > non-functional graphics stack after resuming.  That system doesn't
> > support S3 and the FADT doesn't indicate support for low power idle.
> >
> > Through some experimentation it was concluded that even without the
> > hardware s0i3 support provided by the amd_pmc driver the power
> > consumption over suspend is decreased by running amdgpu's s0ix
> > suspend routine.
> >
> > The numbers over suspend showed:
> > * No patch: 9.2W
> > * Skip amdgpu suspend entirely: 10.5W
> > * Run amdgpu s0ix routine: 7.7W
> >
> > As this does improve the power, remove some of the guard rails in
> > `amdgpu_acpi.c` for only running s0ix suspend routines in the right
> > circumstances.
> >
> > However if this turns out to cause regressions for anyone, we should
> > revert this change and instead opt for skipping suspend/resume routines
> > entirely or try to fix the underlying behavior that makes graphics fail
> > after resume without underlying platform support.
> >
> > Reported-by: Rafael Ávila de Espíndola <rafael at espindo.la>
> > Link: https://gitlab.freedesktop.org/drm/amd/-/issues/2364
> > Signed-off-by: Mario Limonciello <mario.limonciello at amd.com>
> > ---
> >  drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c | 8 ++------
> >  1 file changed, 2 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> > index 57b5e11446c65..fa7375b97fd47 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> > @@ -1079,20 +1079,16 @@ bool amdgpu_acpi_is_s0ix_active(struct
> amdgpu_device *adev)
> >          * S0ix even though the system is suspending to idle, so return false
> >          * in that case.
> >          */
> > -       if (!(acpi_gbl_FADT.flags & ACPI_FADT_LOW_POWER_S0)) {
> > +       if (!(acpi_gbl_FADT.flags & ACPI_FADT_LOW_POWER_S0))
> >                 dev_warn_once(adev->dev,
> >                               "Power consumption will be higher as BIOS has not been
> configured for suspend-to-idle.\n"
> >                               "To use suspend-to-idle change the sleep mode in BIOS
> setup.\n");
> > -               return false;
> 
> Thinking about this more, I think we may need to check the asic type
> here.  Pre-Raven APUs didn't support S0ix at all so this may break
> them if they have any checks that use amdgpu_acpi_is_s0ix_active() in
> their code paths.

For them what should we be doing when they try to do s2idle though?
S3 path?  Or nothing?

> 
> Alex
> 
> 
> > -       }
> >
> >  #if !IS_ENABLED(CONFIG_AMD_PMC)
> >         dev_warn_once(adev->dev,
> >                       "Power consumption will be higher as the kernel has not been
> compiled with CONFIG_AMD_PMC.\n");
> > -       return false;
> > -#else
> > -       return true;
> >  #endif /* CONFIG_AMD_PMC */
> > +       return true;
> >  }
> >
> >  #endif /* CONFIG_SUSPEND */
> > --
> > 2.25.1
> >