linux-kernel - Re: [PATCH] drm/msm/dpu: ensure device suspend happens during PM sleep

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Date:   Fri, 17 Apr 2020 13:56:34 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Kalyan Thota <kalyan_t@...eaurora.org>
Cc:     dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
        Rob Clark <robdclark@...il.com>,
        Sean Paul <seanpaul@...omium.org>,
        "Kristian H. Kristensen" <hoegsberg@...omium.org>,
        Jeykumar Sankaran <jsanka@...eaurora.org>,
        mkrishn@...eaurora.org, travitej@...eaurora.org,
        nganji@...eaurora.org
Subject: Re: [PATCH] drm/msm/dpu: ensure device suspend happens during PM sleep

Hi,

On Fri, Apr 17, 2020 at 12:13 AM Kalyan Thota <kalyan_t@...eaurora.org> wrote:
>
> "The PM core always increments the runtime usage counter
> before calling the ->suspend() callback and decrements it
> after calling the ->resume() callback"
>
> DPU and DSI are managed as runtime devices. When
> suspend is triggered, PM core adds a refcount on all the
> devices and calls device suspend, since usage count is
> already incremented, runtime suspend was not getting called
> and it kept the clocks on which resulted in target not
> entering into XO shutdown.
>
> Add changes to force suspend on runtime devices during pm sleep.
>
> Changes in v1:
>  - Remove unnecessary checks in the function
>     _dpu_kms_disable_dpu (Rob Clark).
>
> Changes in v2:
>  - Avoid using suspend_late to reset the usagecount
>    as suspend_late might not be called during suspend
>    call failures (Doug).
>
> Changes in v3:
>  - Use force suspend instead of managing device usage_count
>    via runtime put and get API's to trigger callbacks (Doug).
>
> Changes in v4:
>  - Check the return values of pm_runtime_force_suspend and
>    pm_runtime_force_resume API's and pass appropriately (Doug).
>
> Signed-off-by: Kalyan Thota <kalyan_t@...eaurora.org>
> ---
>  drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c |  2 ++
>  drivers/gpu/drm/msm/dsi/dsi.c           |  2 ++
>  drivers/gpu/drm/msm/msm_drv.c           | 14 +++++++++++++-
>  3 files changed, 17 insertions(+), 1 deletion(-)

I am most certainly not an expert in this code, but as far as I can
tell it looks sane.  Thus:

Reviewed-by: Douglas Anderson <dianders@...omium.org>

-Doug