linux-kernel - Re: [PATCH v2] drm/rockchip: Skip suspend/resume if no display is attached

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Message-ID: <20170809230543.GA109008@google.com>
Date:   Wed, 9 Aug 2017 16:05:43 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     zijun_hu <zijun_hu@....com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org,
        Doug Anderson <dianders@...omium.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Greg Hackmann <ghackmann@...gle.com>,
        Yury Norov <ynorov@...iumnetworks.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: Re: [PATCH v2] drm/rockchip: Skip suspend/resume if no display is
 attached

El Wed, Aug 09, 2017 at 04:03:02PM -0700 Matthias Kaehlcke ha dit:

> rockchip_drm_sys_suspend/resume() obains a struct drm_device pointer
> from drvdata, the pointer is then dereferenced to obtain private data.
> drvdata is set when a display is bound, on systems without a
> (successfully probed) display drvdata is NULL and the PM functions
> try to dereference a NULL pointer.
> 
> The suspend/resume code relies on a valid drm_device object, skip it if
> the pointer is NULL.

sorry for the noise, the recipient list was taken from the command
history in another tab, instead the one I intended :(

> ---
>  drivers/gpu/drm/rockchip/rockchip_drm_drv.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
> index c6b1b7f3a2a3..6228145d9496 100644
> --- a/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
> +++ b/drivers/gpu/drm/rockchip/rockchip_drm_drv.c
> @@ -275,11 +275,16 @@ static void rockchip_drm_fb_resume(struct drm_device *drm)
>  static int rockchip_drm_sys_suspend(struct device *dev)
>  {
>  	struct drm_device *drm = dev_get_drvdata(dev);
> -	struct rockchip_drm_private *priv = drm->dev_private;
> +	struct rockchip_drm_private *priv;
> +
> +	if (!drm)
> +		/* no display attached */
> +		return 0;
>  
>  	drm_kms_helper_poll_disable(drm);
>  	rockchip_drm_fb_suspend(drm);
>  
> +	priv = drm->dev_private;
>  	priv->state = drm_atomic_helper_suspend(drm);
>  	if (IS_ERR(priv->state)) {
>  		rockchip_drm_fb_resume(drm);
> @@ -293,8 +298,13 @@ static int rockchip_drm_sys_suspend(struct device *dev)
>  static int rockchip_drm_sys_resume(struct device *dev)
>  {
>  	struct drm_device *drm = dev_get_drvdata(dev);
> -	struct rockchip_drm_private *priv = drm->dev_private;
> +	struct rockchip_drm_private *priv;
> +
> +	if (!drm)
> +		/* no display attached */
> +		return 0;
>  
> +	priv = drm->dev_private;
>  	drm_atomic_helper_resume(drm, priv->state);
>  	rockchip_drm_fb_resume(drm);
>  	drm_kms_helper_poll_enable(drm);