linux-kernel - Re: [PATCH v3 5/8] drm/msm/a6xx: Ensure CX collapse during gpu recovery

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Date:   Wed, 3 Aug 2022 14:09:16 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Akhil P Oommen <quic_akhilpo@...cinc.com>
Cc:     freedreno <freedreno@...ts.freedesktop.org>,
        dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
        Rob Clark <robdclark@...il.com>,
        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>,
        Chia-I Wu <olvaffe@...il.com>, Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Sean Paul <sean@...rly.run>,
        Stephen Boyd <swboyd@...omium.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 5/8] drm/msm/a6xx: Ensure CX collapse during gpu recovery

On Wed, 3 Aug 2022 at 13:15, Akhil P Oommen <quic_akhilpo@...cinc.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@...cinc.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@...aro.org>


-- 
With best wishes
Dmitry