[PATCH] drm/amdgpu: keep mmhub clock gating being enabled during s2idle suspend

[Liang, Prike]

[AMD Official Use Only - General]

> -----Original Message-----
> From: Lazar, Lijo <Lijo.Lazar at amd.com>
> Sent: Wednesday, April 27, 2022 2:33 PM
> To: Liang, Prike <Prike.Liang at amd.com>; amd-gfx at lists.freedesktop.org
> Cc: Deucher, Alexander <Alexander.Deucher at amd.com>; Huang, Ray
> <Ray.Huang at amd.com>
> Subject: Re: [PATCH] drm/amdgpu: keep mmhub clock gating being enabled
> during s2idle suspend
>
>
>
> On 4/27/2022 9:44 AM, Liang, Prike wrote:
> > [Public]
> >
> >> -----Original Message-----
> >> From: Lazar, Lijo <Lijo.Lazar at amd.com>
> >> Sent: Tuesday, April 26, 2022 7:19 PM
> >> To: Liang, Prike <Prike.Liang at amd.com>; amd-gfx at lists.freedesktop.org
> >> Cc: Deucher, Alexander <Alexander.Deucher at amd.com>; Huang, Ray
> >> <Ray.Huang at amd.com>
> >> Subject: Re: [PATCH] drm/amdgpu: keep mmhub clock gating being
> >> enabled during s2idle suspend
> >>
> >>
> >>
> >> On 4/25/2022 12:22 PM, Prike Liang wrote:
> >>> Without MMHUB clock gating being enabled then MMHUB will not
> >>> disconnect from DF and will result in DF C-state entry can't be
> >>> accessed during S2idle suspend, and eventually s0ix entry will be blocked.
> >>>
> >>> Signed-off-by: Prike Liang <Prike.Liang at amd.com>
> >>> ---
> >>>    drivers/gpu/drm/amd/amdgpu/gmc_v10_0.c | 10 ++++++++++
> >>>    1 file changed, 10 insertions(+)
> >>>
> >>> diff --git a/drivers/gpu/drm/amd/amdgpu/gmc_v10_0.c
> >>> b/drivers/gpu/drm/amd/amdgpu/gmc_v10_0.c
> >>> index a455e59f41f4..20946bc7fc93 100644
> >>> --- a/drivers/gpu/drm/amd/amdgpu/gmc_v10_0.c
> >>> +++ b/drivers/gpu/drm/amd/amdgpu/gmc_v10_0.c
> >>> @@ -1151,6 +1151,16 @@ static int
> >>> gmc_v10_0_set_clockgating_state(void
> >> *handle,
> >>>      int r;
> >>>      struct amdgpu_device *adev = (struct amdgpu_device *)handle;
> >>>
> >>> +   /*
> >>> +    * The issue mmhub can't disconnect from DF with MMHUB clock
> >> gating being disabled
> >>> +    * is a new problem observed at DF 3.0.3, however with the same
> >> suspend sequence not
> >>> +    * seen any issue on the DF 3.0.2 series platform.
> >>> +    */
> >>> +   if (adev->in_s0ix && adev->ip_versions[DF_HWIP][0] >
> >>> + IP_VERSION(3,
> >> 0, 2)) {
> >>> +           dev_dbg(adev->dev, "keep mmhub clock gating being
> >> enabled for s0ix\n");
> >>> +           return 0;
> >>> +   }
> >>> +
> >>
> >> This only ignores clock gating requests as long as s0ix flag is set.
> >> As far as I see, s0ix flag is set to true even during resume and set
> >> to false only after resume is completed. Is that intention and is
> >> this tested to be working fine? I suggest to keep this specifically for
> suspend calls.
> >>
> >> Thanks,
> >> Lijo
> >>
> > It reasonable for also not reenable the clock gating on the s2ilde
> > resume since clock gating not disabled on the s2idle suspend.
>
> Generally, the CG setting registers are not in always-on domain and the
> register settings will be lost once it goes down. Not sure about the state of
> this particular IP rail during S0i3 cycle.
>
> If the CG settings are driver-enabled, we reprogram CG settings during
> resume - amdgpu_device_resume->amdgpu_device_ip_late_init ->
> amdgpu_device_set_cg_state. This logic prevents this. Maybe, it works fine
> during your testing because it's done by FW. If the settings are programmed
> by FW components, usually reprogramming is taken care by FW.
>
> Thanks,
> Lijo
>
In the S0i3 entry the gfx power rail will be turn off but MEM_S3 power rail is keeping on and involved device/IP context will be saved in the memory and then each context restored by PM firmware during S0i3 resume.

> Have merged the fix for not blocking s0ix support for some
> > upcoming asic and meanwhile still need dig into whether the DF C-state,
> MMHUB DS or BIOS mmhub power gate request different on GC 10.3.7
> introduce this issue and then make a generic solution for such this issue.
> >
> >>>      r = adev->mmhub.funcs->set_clockgating(adev, state);
> >>>      if (r)
> >>>              return r;
> >>>