linux-kernel - Re: [PATCH] drm/msm: Grab the GPU runtime in a6xx routines, not the GMU one

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Date:   Thu, 9 Jun 2022 21:34:58 +0530
From:   Akhil P Oommen <quic_akhilpo@...cinc.com>
To:     Rob Clark <robdclark@...il.com>,
        Douglas Anderson <dianders@...omium.org>
CC:     Jordan Crouse <jordan@...micpenguin.net>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Chia-I Wu <olvaffe@...il.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        "Dmitry Baryshkov" <dmitry.baryshkov@...aro.org>,
        Eric Anholt <eric@...olt.net>,
        Jonathan Marek <jonathan@...ek.ca>,
        Sean Paul <sean@...rly.run>, Wang Qing <wangqing@...o.com>,
        Yangtao Li <tiny.windzz@...il.com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/msm: Grab the GPU runtime in a6xx routines, not the
 GMU one

On 6/9/2022 9:24 PM, Rob Clark wrote:
> On Thu, Jun 9, 2022 at 7:34 AM Douglas Anderson <dianders@...omium.org> wrote:
>>  From testing on sc7180-trogdor devices, reading the GMU registers
>> needs the GMU clocks to be enabled. Those clocks get turned on in
>> a6xx_gmu_resume(). Confusingly enough, that function is called as a
>> result of the runtime_pm of the GPU "struct device", not the GMU
>> "struct device".
>>
>> Let's grab a reference to the correct device. Incidentally, this makes
>> us match the a5xx routine more closely.
>>
>> This is easily shown to fix crashes that happen if we change the GPU's
>> pm_runtime usage to not use autosuspend. It's also believed to fix
>> some long tail GPU crashes even with autosuspend.
>>
>> NOTE: the crashes I've seen were fixed by _only_ fixing
>> a6xx_gpu_busy(). However, I believe that the same arguments should be
>> made to a6xx_gmu_set_freq() so I've changed that function too.
>>
>> Fixes: eadf79286a4b ("drm/msm: Check for powered down HW in the devfreq callbacks")
>> Signed-off-by: Douglas Anderson <dianders@...omium.org>
>> ---
>>
>>   drivers/gpu/drm/msm/adreno/a6xx_gmu.c | 6 +++---
>>   drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 4 ++--
>>   2 files changed, 5 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
>> index 9f76f5b15759..b79ad2e0649c 100644
>> --- a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
>> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
>> @@ -129,13 +129,13 @@ void a6xx_gmu_set_freq(struct msm_gpu *gpu, struct dev_pm_opp *opp)
>>           * This can get called from devfreq while the hardware is idle. Don't
>>           * bring up the power if it isn't already active
>>           */
>> -       if (pm_runtime_get_if_in_use(gmu->dev) == 0)
>> +       if (pm_runtime_get_if_in_use(&gpu->pdev->dev) == 0)
> IMHO, if we do end up using the GPU's runpm instead of the GMU's, we
> should probably just move this _get_if_in_use() into msm_gpu_devfreq,
+ 1 this.
> etc.  (And probably also this should be "<= 0".. I have that change
> locally but haven't sent a patch yet
.. and skip return here when CONFIG_PM is disabled.

-Akhil.
>
> BR,
> -R
>
>>                  return;
>>
>>          if (!gmu->legacy) {
>>                  a6xx_hfi_set_freq(gmu, perf_index);
>>                  dev_pm_opp_set_opp(&gpu->pdev->dev, opp);
>> -               pm_runtime_put(gmu->dev);
>> +               pm_runtime_put(&gpu->pdev->dev);
>>                  return;
>>          }
>>
>> @@ -159,7 +159,7 @@ void a6xx_gmu_set_freq(struct msm_gpu *gpu, struct dev_pm_opp *opp)
>>                  dev_err(gmu->dev, "GMU set GPU frequency error: %d\n", ret);
>>
>>          dev_pm_opp_set_opp(&gpu->pdev->dev, opp);
>> -       pm_runtime_put(gmu->dev);
>> +       pm_runtime_put(&gpu->pdev->dev);
>>   }
>>
>>   unsigned long a6xx_gmu_get_freq(struct msm_gpu *gpu)
>> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
>> index 841e47a0b06b..87568d0b6ef8 100644
>> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
>> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
>> @@ -1659,7 +1659,7 @@ static u64 a6xx_gpu_busy(struct msm_gpu *gpu, unsigned long *out_sample_rate)
>>          *out_sample_rate = 19200000;
>>
>>          /* Only read the gpu busy if the hardware is already active */
>> -       if (pm_runtime_get_if_in_use(a6xx_gpu->gmu.dev) == 0)
>> +       if (pm_runtime_get_if_in_use(&gpu->pdev->dev) == 0)
>>                  return 0;
>>
>>          busy_cycles = gmu_read64(&a6xx_gpu->gmu,
>> @@ -1667,7 +1667,7 @@ static u64 a6xx_gpu_busy(struct msm_gpu *gpu, unsigned long *out_sample_rate)
>>                          REG_A6XX_GMU_CX_GMU_POWER_COUNTER_XOCLK_0_H);
>>
>>
>> -       pm_runtime_put(a6xx_gpu->gmu.dev);
>> +       pm_runtime_put(&gpu->pdev->dev);
>>
>>          return busy_cycles;
>>   }
>> --
>> 2.36.1.255.ge46751e96f-goog
>>