linux-kernel - Re: [PATCH v2 2/2] drm/msm/adreno: Setup SMMU aparture for per-process page table

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Message-ID: <CADLxj5SvwUxgkXOrayyuJo-Jw7LQnV4vOoFW93unPwxfoMpMNQ@mail.gmail.com>
Date: Tue, 19 Nov 2024 10:31:30 -0600
From: Bjorn Andersson <bjorn.andersson@....qualcomm.com>
To: Akhil P Oommen <quic_akhilpo@...cinc.com>
Cc: Rob Clark <robdclark@...il.com>, Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>, Sean Paul <sean@...rly.run>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>,
        Jessica Zhang <quic_jesszhan@...cinc.com>,
        Simona Vetter <simona@...ll.ch>, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org
Subject: Re: [PATCH v2 2/2] drm/msm/adreno: Setup SMMU aparture for
 per-process page table

On Tue, Nov 12, 2024 at 3:15 PM Akhil P Oommen <quic_akhilpo@...cinc.com> wrote:
>
> On 11/11/2024 8:38 PM, Rob Clark wrote:
> > On Sun, Nov 10, 2024 at 9:31 AM Bjorn Andersson
> > <bjorn.andersson@....qualcomm.com> wrote:
> >>
> >> Support for per-process page tables requires the SMMU aparture to be
> >> setup such that the GPU can make updates with the SMMU. On some targets
> >> this is done statically in firmware, on others it's expected to be
> >> requested in runtime by the driver, through a SCM call.
> >>
> >> One place where configuration is expected to be done dynamically is the
> >> QCS6490 rb3gen2.
> >>
> >> The downstream driver does this unconditioanlly on any A6xx and newer,
> >
> > nit, s/unconditioanlly/unconditionally/
> >
> >> so follow suite and make the call.
> >>
> >> Signed-off-by: Bjorn Andersson <bjorn.andersson@....qualcomm.com>
> >
> > Reviewed-by: Rob Clark <robdclark@...il.com>
> >
> >
> >> ---
> >>  drivers/gpu/drm/msm/adreno/adreno_gpu.c | 11 +++++++++++
> >>  1 file changed, 11 insertions(+)
> >>
> >> diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.c b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> >> index 076be0473eb5..75f5367e73ca 100644
> >> --- a/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> >> +++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.c
> >> @@ -572,8 +572,19 @@ struct drm_gem_object *adreno_fw_create_bo(struct msm_gpu *gpu,
> >>
> >>  int adreno_hw_init(struct msm_gpu *gpu)
> >>  {
>
> SCM calls into TZ can block for a very long time (seconds). It depends
> on concurrent activities from other drivers like crypto for eg:. So we
> should not do this in the gpu wake up path.
>
> Practically, gpu probe is the better place to do this.
>

Thanks for your feedback, Akhil!

I've yet to see SCM calls take that long, but we don't want that in
the wakeup path, so I have no concerns about moving this call to probe
time if that works.
Based on conversation with Rob I merged the two patches through the
qcom-soc tree, so they are expected to show up in v6.13-rc1.

Let's follow up with a patch that moves the call, once -rc1 is out.
That said, I don't have any means currently to test the retention part...

Thanks,
Bjorn