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

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Message-ID: <CAD=FV=WcFahUm8jK+QTwx7BkCb3GTgKqFLP_pdqWBqN-zawrbw@mail.gmail.com>
Date:   Mon, 30 Mar 2020 11:55:25 -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 Mon, Mar 30, 2020 at 2:04 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 manage 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).
>
> Signed-off-by: Kalyan Thota <kalyan_t@...eaurora.org>
> ---
>  drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c | 33 +++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/msm/msm_drv.c           |  4 ++++
>  drivers/gpu/drm/msm/msm_kms.h           |  2 ++
>  3 files changed, 39 insertions(+)

I am still 100% baffled by your patch and I never did quite understand
your response to my previous comments [1].  I think you're saying that
the problem you were facing is that if you call "suspend" but never
called "runtime_suspend" that the device stays active.  Is that right?
 If that's true, did you try something like this suggestion I made?

SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend, pm_runtime_force_resume)


> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> index ce19f1d..2343cbd 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> @@ -26,6 +26,7 @@
>  #include "dpu_encoder.h"
>  #include "dpu_plane.h"
>  #include "dpu_crtc.h"
> +#include "dsi.h"
>
>  #define CREATE_TRACE_POINTS
>  #include "dpu_trace.h"
> @@ -325,6 +326,37 @@ static void dpu_kms_disable_commit(struct msm_kms *kms)
>         pm_runtime_put_sync(&dpu_kms->pdev->dev);
>  }
>
> +static void _dpu_kms_disable_dpu(struct msm_kms *kms)
> +{
> +       struct dpu_kms *dpu_kms = to_dpu_kms(kms);
> +       struct drm_device *dev = dpu_kms->dev;
> +       struct msm_drm_private *priv = dev->dev_private;
> +       struct msm_dsi *dsi;
> +       int i;
> +
> +       dpu_kms_disable_commit(kms);
> +
> +       for (i = 0; i < ARRAY_SIZE(priv->dsi); i++) {
> +               if (!priv->dsi[i])
> +                       continue;
> +               dsi = priv->dsi[i];
> +               pm_runtime_put_sync(&dsi->pdev->dev);
> +       }
> +       pm_runtime_put_sync(dev->dev);
> +
> +       /* Increment the usagecount without triggering a resume */
> +       pm_runtime_get_noresume(dev->dev);
> +
> +       pm_runtime_get_noresume(&dpu_kms->pdev->dev);
> +
> +       for (i = 0; i < ARRAY_SIZE(priv->dsi); i++) {
> +               if (!priv->dsi[i])
> +                       continue;
> +               dsi = priv->dsi[i];
> +               pm_runtime_get_noresume(&dsi->pdev->dev);
> +       }
> +}

My pm_runtime knowledge is pretty weak sometimes, but the above
function looks crazy.  Maybe it's just me not understanding, but can
you please summarize what you're trying to accomplish?

-Doug

[1] https://lore.kernel.org/r/114130f68c494f83303c51157e2c5bfa@codeaurora.org