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

[Rafael Ávila de Espíndola]

As far as I know the "no S3 if SMT off" is just an oddity of the
particular BIOS I got on the "B550I AORUS PRO AX".

Also, what has changed that would prevent the same issue I was hitting
before?:

https://gitlab.freedesktop.org/drm/amd/-/issues/2364#note_1735422

Cheers,
Rafael

"Limonciello, Mario" <Mario.Limonciello at amd.com> writes:

> [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
>> >