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From:   Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Date:   Wed, 3 Aug 2022 14:09:16 +0300
Message-ID: <CAA8EJppAprzF5S-zvYYo53QenosUkXU49kiWWzWndVwhWZgS7Q@mail.gmail.com>
Subject: Re: [PATCH v3 5/8] drm/msm/a6xx: Ensure CX collapse during gpu recovery
To:     Akhil P Oommen <quic_akhilpo@quicinc.com>
Cc:     freedreno <freedreno@lists.freedesktop.org>,
        dri-devel@lists.freedesktop.org, linux-arm-msm@vger.kernel.org,
        Rob Clark <robdclark@gmail.com>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Jordan Crouse <jordan@cosmicpenguin.net>,
        Jonathan Marek <jonathan@marek.ca>,
        Douglas Anderson <dianders@chromium.org>,
        Matthias Kaehlcke <mka@chromium.org>,
        Abhinav Kumar <quic_abhinavk@quicinc.com>,
        Chia-I Wu <olvaffe@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
        David Airlie <airlied@linux.ie>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        Sean Paul <sean@poorly.run>,
        Stephen Boyd <swboyd@chromium.org>,
        linux-kernel@vger.kernel.org
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On Wed, 3 Aug 2022 at 13:15, Akhil P Oommen <quic_akhilpo@quicinc.com> wrote:
>
> On 8/2/2022 12:44 PM, Dmitry Baryshkov wrote:
> > On 30/07/2022 12:40, Akhil P Oommen wrote:
> >> Because there could be transient votes from other drivers/tz/hyp which
> >> may keep the cx gdsc enabled, we should poll until cx gdsc collapses.
> >> We can use the reset framework to poll for cx gdsc collapse from gpucc
> >> clk driver.
> >>
> >> This feature requires support from the platform's gpucc driver.
> >>
> >> Signed-off-by: Akhil P Oommen <quic_akhilpo@quicinc.com>
> >> ---
> >>
> >> Changes in v3:
> >> - Use reset interface from gpucc driver to poll for cx gdsc collapse
> >>    https://patchwork.freedesktop.org/series/106860/
> >>
> >>   drivers/gpu/drm/msm/adreno/a6xx_gpu.c | 4 ++++
> >>   drivers/gpu/drm/msm/msm_gpu.c         | 4 ++++
> >>   drivers/gpu/drm/msm/msm_gpu.h         | 4 ++++
> >>   3 files changed, 12 insertions(+)
> >>
> >> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> >> b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> >> index 1b049c5..721d5e6 100644
> >> --- a/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> >> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gpu.c
> >> @@ -10,6 +10,7 @@
> >>     #include <linux/bitfield.h>
> >>   #include <linux/devfreq.h>
> >> +#include <linux/reset.h>
> >>   #include <linux/soc/qcom/llcc-qcom.h>
> >>     #define GPU_PAS_ID 13
> >> @@ -1224,6 +1225,9 @@ static void a6xx_recover(struct msm_gpu *gpu)
> >>       /* And the final one from recover worker */
> >>       pm_runtime_put_sync(&gpu->pdev->dev);
> >>   +    /* Call into gpucc driver to poll for cx gdsc collapse */
> >> +    reset_control_reset(gpu->cx_collapse);
> >
> > Do we have a race between the last pm_runtime_put_sync(), this polling
> > and other voters removing their votes beforehand?
> I can't see any issue with a race here. reset_control_reset() will
> return immediately in that case.

Ack, ok then.

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>


-- 
With best wishes
Dmitry