[PATCH 1/2] drm/amd: Disallow s0ix without BIOS support again

[Limonciello, Mario]

[AMD Official Use Only - General]

> -----Original Message-----
> From: Alex Deucher <alexdeucher at gmail.com>
> Sent: Tuesday, May 30, 2023 1:16 PM
> 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 1/2] drm/amd: Disallow s0ix without BIOS support again
>
> On Tue, May 30, 2023 at 1:53 PM Mario Limonciello
> <mario.limonciello at amd.com> wrote:
> >
> > commit cf488dcd0ab7 ("drm/amd: Allow s0ix without BIOS support")
> showed
> > improvements to power consumption over suspend when s0ix wasn't
> enabled in
> > BIOS and the system didn't support S3.
> >
> > This patch however was misguided because the reason the system didn't
> > support S3 was because SMT was disabled in OEM BIOS setup.
> > This prevented the BIOS from allowing S3.
> >
> > Also allowing GPUs to use the s2idle path actually causes problems if
> > they're invoked on systems that may not support s2idle in the platform
> > firmware. `systemd` has a tendency to try to use `s2idle` if `deep` fails
> > for any reason, which could lead to unexpected flows.
> >
> > To make this the behavior discoverable and expected, revert commit
> > cf488dcd0ab7 ("drm/amd: Allow s0ix without BIOS support") and offer
> > a message if SMT appears to be disabled.
> >
> > Cc: Rafael Ávila de Espíndola <rafael at espindo.la>
> > Link:
> https://github.com/torvalds/linux/blob/v6.1/drivers/gpu/drm/amd/amdgpu
> /amdgpu_acpi.c#L1060
> > Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/2599
> > Signed-off-by: Mario Limonciello <mario.limonciello at amd.com>
> > ---
> >  drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c | 16 ++++++++++++++--
> >  1 file changed, 14 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> > index 3a6b2e2089f6..a3523d03d769 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> > @@ -28,6 +28,7 @@
> >  #include <linux/xarray.h>
> >  #include <linux/power_supply.h>
> >  #include <linux/pm_runtime.h>
> > +#include <linux/sched/smt.h>
> >  #include <linux/suspend.h>
> >  #include <acpi/video.h>
> >  #include <acpi/actbl.h>
> > @@ -1473,6 +1474,13 @@ void amdgpu_acpi_release(void)
> >   */
> >  bool amdgpu_acpi_is_s3_active(struct amdgpu_device *adev)
> >  {
> > +#ifdef CONFIG_X86
> > +       if (!sched_smt_active()) {
> > +               dev_warn_once(adev->dev,
> > +                             "SMT is disabled by the BIOS.\n"
> > +                             "To use suspend-to-ram enable SMT in BIOS setup.\n");
> > +       }
> > +#endif
>
> Will this generate a spurious warning on platforms that are natively non-SMT?

Yeah; it could.  I'm not sure how we can reliably detect this.  I thought about looking for
the 'ht' flag, but that probably wouldn't work for this case.

Are there AMD Zen CPUs or APUs that are non-SMT?  Could gate the sched_smt_active()
check to only run when it's an AMD x86 Zen SoC.

>
> Alex
>
> >         return !(adev->flags & AMD_IS_APU) ||
> >                 (pm_suspend_target_state == PM_SUSPEND_MEM);
> >  }
> > @@ -1499,16 +1507,20 @@ 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;
> > +       }
> >
> >  #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");
> > -#endif /* CONFIG_AMD_PMC */
> > +       return false;
> > +#else
> >         return true;
> > +#endif /* CONFIG_AMD_PMC */
> >  }
> >
> >  #endif /* CONFIG_SUSPEND */
> > --
> > 2.34.1
> >