linux-kernel - Re: [PATCH 2/2] drm: hdlcd: Suspend/resume only active crtcs

Open Source and information security mailing list archives

Date:	Thu, 5 May 2016 19:06:02 +0200
From:	Daniel Vetter <daniel@...ll.ch>
To:	Robin Murphy <robin.murphy@....com>
Cc:	airlied@...ux.ie, liviu.dudau@....com,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/2] drm: hdlcd: Suspend/resume only active crtcs

On Thu, May 05, 2016 at 05:13:38PM +0100, Robin Murphy wrote:
> The current PM ops simply unconditionally enable/disable the HDLCD,
> which proves problematic when there is no display plugged in - since
> without a crtc the hardware itself is still in an uninitialised state,
> coming out of suspend results in it being enabled without a valid
> framebuffer address, which typically results in it trying to scan out
> from bus address 0 and flooding the system with error interrupts.
> 
> Fix this by checking the crtc state on resume, and only enabling the
> hardware if it's actually supposed to be. For the sake of consistency,
> do the same on the suspend path as well, although there it's merely a
> case of skipping unnecessary work.
> 
> CC: Liviu Dudau <liviu.dudau@....com>
> Signed-off-by: Robin Murphy <robin.murphy@....com>
> ---
>  drivers/gpu/drm/arm/hdlcd_crtc.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/arm/hdlcd_crtc.c b/drivers/gpu/drm/arm/hdlcd_crtc.c
> index fef1b04c2aab..bf6ff5e48adc 100644
> --- a/drivers/gpu/drm/arm/hdlcd_crtc.c
> +++ b/drivers/gpu/drm/arm/hdlcd_crtc.c
> @@ -296,12 +296,14 @@ static struct drm_plane *hdlcd_plane_init(struct drm_device *drm)
>  
>  void hdlcd_crtc_suspend(struct drm_crtc *crtc)
>  {
> -	hdlcd_crtc_disable(crtc);
> +	if (crtc->state->active)
> +		hdlcd_crtc_disable(crtc);
>  }
>  
>  void hdlcd_crtc_resume(struct drm_crtc *crtc)
>  {
> -	hdlcd_crtc_enable(crtc);
> +	if (crtc->state->active)
> +		hdlcd_crtc_enable(crtc);
>  }

If you use the atomic helpers to suspend/resume your entire display
pipeline these callbacks shouldn't even be needed at all. Tried just
removing them?
-Daniel

>  
>  int hdlcd_setup_crtc(struct drm_device *drm)
> -- 
> 2.8.1.dirty
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@...ts.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

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