linux-kernel - Re: [v1] drm/msm: Remove clock and bandwidth votes in mdss pm suspend

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Date:   Sun, 17 Feb 2019 12:40:27 -0500
From:   Rob Clark <robdclark@...il.com>
To:     Jayant Shekhar <jshekhar@...eaurora.org>
Cc:     dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        freedreno <freedreno@...ts.freedesktop.org>,
        devicetree@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Sean Paul <seanpaul@...omium.org>,
        "Kristian H. Kristensen" <hoegsberg@...omium.org>,
        Abhinav Kumar <abhinavk@...eaurora.org>,
        Jeykumar Sankaran <jsanka@...eaurora.org>,
        chandanu@...eaurora.org, nganji@...eaurora.org
Subject: Re: [v1] drm/msm: Remove clock and bandwidth votes in mdss pm suspend

On Wed, Jan 23, 2019 at 6:12 AM Jayant Shekhar <jshekhar@...eaurora.org> wrote:
>
> MDSS PM suspend is dependent on runtime suspend for disabling
> clocks and removing bandwidth votes. In case of pm_suspend
> triggered, dpm_prepare hold a refcount on power usage of device
> and hence runtime suspend is never triggered during pm_suspend.
> As runtime suspend is not triggered, clocks and bandwidth votes
> remain. Hence explicitly trigger mdss disable in msm_pm_suspend
> to disable clocks and remove the votes.
>
> Signed-off-by: Jayant Shekhar <jshekhar@...eaurora.org>
> ---
>  drivers/gpu/drm/msm/msm_drv.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c
> index 5c60bb3..ffe3a25 100644
> --- a/drivers/gpu/drm/msm/msm_drv.c
> +++ b/drivers/gpu/drm/msm/msm_drv.c
> @@ -1068,12 +1068,16 @@ static int msm_pm_suspend(struct device *dev)
>  {
>         struct drm_device *ddev = dev_get_drvdata(dev);
>         struct msm_drm_private *priv = ddev->dev_private;
> +       struct msm_mdss *mdss = priv->mdss;
>
>         if (!IS_ERR_OR_NULL(priv->pm_state))
>                 return 0;
>
>         priv->pm_state = drm_atomic_helper_suspend(ddev);
>
> +       if (mdss && mdss->funcs)
> +               mdss->funcs->disable(mdss);
> +

This patch doesn't actually seem to apply, I guess it has a dependency
on some other missing patch?

That said, shouldn't the refcount aquired in _prepare() be dropped
somewhere?  It seems like if all planes/crtcs/etc are disabled, we
should also disable power (or at least as much as we can while still
having hotplug work), so ideally drm_atomic_helper_suspend() should be
enough.

BR.
-R

>         return IS_ERR(priv->pm_state) ? PTR_ERR(priv->pm_state) : 0;
>  }
>
> @@ -1081,11 +1085,15 @@ static int msm_pm_resume(struct device *dev)
>  {
>         struct drm_device *ddev = dev_get_drvdata(dev);
>         struct msm_drm_private *priv = ddev->dev_private;
> +       struct msm_mdss *mdss = priv->mdss;
>         int ret;
>
>         if (IS_ERR_OR_NULL(priv->pm_state))
>                 return 0;
>
> +       if (mdss && mdss->funcs)
> +               mdss->funcs->enable(mdss);
> +
>         ret = drm_atomic_helper_resume(ddev, priv->pm_state);
>         if (ret == 0)
>                 priv->pm_state = NULL;
> --
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> a Linux Foundation Collaborative Project
>