linux-kernel - Re: [PATCH v6] drm/msm/dpu: ensure device suspend happens during PM sleep

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Date:   Thu, 4 Jun 2020 13:34:05 -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 v6] drm/msm/dpu: ensure device suspend happens during PM sleep

Hi,

On Thu, Jun 4, 2020 at 6:20 AM Kalyan Thota <kalyan_t@...eaurora.org> wrote:
>
> -#ifdef CONFIG_PM
> -static int msm_runtime_suspend(struct device *dev)
> +#ifdef CONFIG_PM_SLEEP
> +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;
>

nit: remove blank line at the start of this function

>  static const struct dev_pm_ops msm_pm_ops = {
>         SET_SYSTEM_SLEEP_PM_OPS(msm_pm_suspend, msm_pm_resume)
>         SET_RUNTIME_PM_OPS(msm_runtime_suspend, msm_runtime_resume, NULL)
> +       .prepare = msm_pm_prepare,
> +       .complete = msm_pm_complete,

Presumably you will get a compile failure if someone compiles without
CONFIG_PM_SLEEP since msm_pm_prepare() and msm_pm_complete() won't be
defined but you refer to them unconditionally.  Probably the best
solution is to just add "__maybe_unused" to your prepare/complete
function and then always define them.

I can't say I've thought through every corner case but at least this
change no longer raises alarm bells in my mind when I look at it.  ;-)
 If it works for you and nobody else has objections then it seems good
enough and we can always make more improvements later.  Feel free to
add my Reviewed-by tag when my nit is fixed and you make sure it
compiles even if CONFIG_PM_SLEEP isn't defined.

-Doug