linux-kernel - Re: [PATCH v2 3/7] drm/msm: Fix cx collapse issue during recovery

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Message-ID: <CAD=FV=U=J+yf6Qu0VgJ8A5Lhs_s8Fszw=Oa0XUny5XT-5z56xQ@mail.gmail.com>
Date:   Mon, 11 Jul 2022 16:22:25 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Akhil P Oommen <quic_akhilpo@...cinc.com>
Cc:     freedreno <freedreno@...ts.freedesktop.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Rob Clark <robdclark@...il.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Jonathan Marek <jonathan@...ek.ca>,
        Jordan Crouse <jordan@...micpenguin.net>,
        Matthias Kaehlcke <mka@...omium.org>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Chia-I Wu <olvaffe@...il.com>, Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Sean Paul <sean@...rly.run>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/7] drm/msm: Fix cx collapse issue during recovery

Hi,

On Fri, Jul 8, 2022 at 11:00 PM Akhil P Oommen <quic_akhilpo@...cinc.com> wrote:
>
> There are some hardware logic under CX domain. For a successful
> recovery, we should ensure cx headswitch collapses to ensure all the
> stale states are cleard out. This is especially true to for a6xx family
> where we can GMU co-processor.
>
> Currently, cx doesn't collapse due to a devlink between gpu and its
> smmu. So the *struct gpu device* needs to be runtime suspended to ensure
> that the iommu driver removes its vote on cx gdsc.
>
> Signed-off-by: Akhil P Oommen <quic_akhilpo@...cinc.com>
> ---
>
> (no changes since v1)
>
>  drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 16 ++++++++++++++--
>  drivers/gpu/drm/msm/msm_gpu.c         |  2 --
>  2 files changed, 14 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> index 4d50110..7ed347c 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> @@ -1278,8 +1278,20 @@ static void a6xx_recover(struct msm_gpu *gpu)
>          */
>         gmu_write(&a6xx_gpu->gmu, REG_A6XX_GMU_GMU_PWR_COL_KEEPALIVE, 0);
>
> -       gpu->funcs->pm_suspend(gpu);
> -       gpu->funcs->pm_resume(gpu);
> +       /*
> +        * Now drop all the pm_runtime usage count to allow cx gdsc to collapse.
> +        * First drop the usage count from all active submits
> +        */
> +       for (i = gpu->active_submits; i > 0; i--)
> +               pm_runtime_put(&gpu->pdev->dev);
> +
> +       /* And the final one from recover worker */
> +       pm_runtime_put_sync(&gpu->pdev->dev);
> +
> +       for (i = gpu->active_submits; i > 0; i--)
> +               pm_runtime_get(&gpu->pdev->dev);
> +
> +       pm_runtime_get_sync(&gpu->pdev->dev);

In response to v1, Rob suggested pm_runtime_force_suspend/resume().
Those seem like they would work to me, too. Why not use them?