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

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Date:   Tue, 12 Jul 2022 10:34:54 +0530
From:   Akhil P Oommen <quic_akhilpo@...cinc.com>
To:     Doug Anderson <dianders@...omium.org>
CC:     Sean Paul <sean@...rly.run>, Jonathan Marek <jonathan@...ek.ca>,
        "David Airlie" <airlied@...ux.ie>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Rob Clark <robdclark@...il.com>,
        Matthias Kaehlcke <mka@...omium.org>,
        Daniel Vetter <daniel@...ll.ch>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        "Jordan Crouse" <jordan@...micpenguin.net>,
        freedreno <freedreno@...ts.freedesktop.org>,
        Chia-I Wu <olvaffe@...il.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [Freedreno] [PATCH v2 3/7] drm/msm: Fix cx collapse issue during
 recovery

On 7/12/2022 4:52 AM, Doug Anderson wrote:
> 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?
Quoting my previous response which I seem to have sent only to Freedreno 
list:

"I believe it is supposed to be used only during system sleep state 
transitions. Btw, we don't want pm_runtime_get() calls from elsewhere to 
fail by disabling RPM here."

-Akhil