linux-kernel - Re: [PATCH v3 2/8] drm/msm: Take single rpm refcount on behalf of all submits

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Date:   Sun, 31 Jul 2022 22:02:32 +0530
From:   Akhil P Oommen <quic_akhilpo@...cinc.com>
To:     Rob Clark <robdclark@...il.com>
CC:     freedreno <freedreno@...ts.freedesktop.org>,
        <dri-devel@...ts.freedesktop.org>, <linux-arm-msm@...r.kernel.org>,
        "Bjorn Andersson" <bjorn.andersson@...aro.org>,
        Jordan Crouse <jordan@...micpenguin.net>,
        Jonathan Marek <jonathan@...ek.ca>,
        "Douglas Anderson" <dianders@...omium.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Sean Paul <sean@...rly.run>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 2/8] drm/msm: Take single rpm refcount on behalf of all
 submits

On 7/31/2022 9:26 PM, Rob Clark wrote:
> On Sat, Jul 30, 2022 at 2:41 AM Akhil P Oommen <quic_akhilpo@...cinc.com> wrote:
>> Instead of separate refcount for each submit, take single rpm refcount
>> on behalf of all the submits. This makes it easier to drop the rpm
>> refcount during recovery in an upcoming patch.
>>
>> Signed-off-by: Akhil P Oommen <quic_akhilpo@...cinc.com>
>> ---
>>
>> (no changes since v1)
> I see no earlier version of this patch?
>
>>   drivers/gpu/drm/msm/msm_gpu.c | 12 ++++++++----
>>   1 file changed, 8 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/msm/msm_gpu.c b/drivers/gpu/drm/msm/msm_gpu.c
>> index c8cd9bf..e1dd3cc 100644
>> --- a/drivers/gpu/drm/msm/msm_gpu.c
>> +++ b/drivers/gpu/drm/msm/msm_gpu.c
>> @@ -663,11 +663,12 @@ static void retire_submit(struct msm_gpu *gpu, struct msm_ringbuffer *ring,
>>          mutex_lock(&gpu->active_lock);
>>          gpu->active_submits--;
>>          WARN_ON(gpu->active_submits < 0);
>> -       if (!gpu->active_submits)
>> +       if (!gpu->active_submits) {
>>                  msm_devfreq_idle(gpu);
>> -       mutex_unlock(&gpu->active_lock);
>> +               pm_runtime_put_autosuspend(&gpu->pdev->dev);
>> +       }
>>
>> -       pm_runtime_put_autosuspend(&gpu->pdev->dev);
>> +       mutex_unlock(&gpu->active_lock);
>>
>>          msm_gem_submit_put(submit);
>>   }
>> @@ -756,14 +757,17 @@ void msm_gpu_submit(struct msm_gpu *gpu, struct msm_gem_submit *submit)
>>
>>          /* Update devfreq on transition from idle->active: */
>>          mutex_lock(&gpu->active_lock);
>> -       if (!gpu->active_submits)
>> +       if (!gpu->active_submits) {
>> +               pm_runtime_get(&gpu->pdev->dev);
>>                  msm_devfreq_active(gpu);
>> +       }
>>          gpu->active_submits++;
>>          mutex_unlock(&gpu->active_lock);
>>
>>          gpu->funcs->submit(gpu, submit);
>>          gpu->cur_ctx_seqno = submit->queue->ctx->seqno;
>>
>> +       pm_runtime_put(&gpu->pdev->dev);
> this looks unbalanced?
There is another pm_runtime_get_sync at the top of this function. Just 
before hw_init().
https://elixir.bootlin.com/linux/v5.19-rc8/source/drivers/gpu/drm/msm/msm_gpu.c#L737

-Akhil.
>
> BR,
> -R
>
>>          hangcheck_timer_reset(gpu);
>>   }
>>
>> --
>> 2.7.4
>>