[BUG] hdlcd gets confused about base address

[Liviu Dudau]

On Mon, Nov 21, 2016 at 06:16:16PM +0000, Russell King - ARM Linux wrote:
> On Mon, Nov 21, 2016 at 05:56:02PM +0000, Russell King - ARM Linux wrote:
> > For me, the image shift was 100% reproducable.  With the above patch
> > and a call to drm_crtc_vblank_on() in the enable path, it seems to
> > behave correctly - I can alternately switch between 1920x1080 and
> > 1280x1024 and it behaves correctly.  Indeed, my debug prints show that
> > the right thing is happening wrt disabling the controller:
> 
> Here's my version of your patch:

Thanks! I'll add it to my tree and see if David Airlie is happy to push it
this late into the release cycle. Otherwise it is going to end up in linux-next
quickly and then in drm-next before v4.10.

> 
> 8<=============
> From: Russell King <rmk+kernel at armlinux.org.uk>
> Subject: [PATCH] drm/arm: hdlcd: fix plane base address update
> 
> While testing HDMI with Xorg on the Juno board, I find that when Xorg
> starts up or shuts down, the display is shifted significantly to the
> right and wrapped in the active region.  (No sync bars are visible.)
> The timings are correct, it behaves as if the start address has been
> shifted many pixels _into_ the framebuffer.
> 
> This occurs whenever the display mode size is changed - using xrandr
> in Xorg shows that changing the resolution triggers the problem
> almost every time, but changing the refresh rate does not.
> 
> Using devmem2 to disable and re-enable the HDLCD resolves the issue,
> and repeated disable/enable cycles do not make the issue re-appear.
> Further debugging shows that we try to update the controller
> configuration while enabled.
> 
> Alwys ensure that the HDLCD is disabled prior to updating the
> controller timings, and use drm_crtc_vblank_off()/drm_crtc_vblank_on()
> so that DRM knows whether it can expect vblank interrupts.
> 
> Signed-off-by: Russell King <rmk+kernel at armlinux.org.uk>

Acked-by: Liviu Dudau <Liviu.Dudau at arm.com>

> ---
>  drivers/gpu/drm/arm/hdlcd_crtc.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/arm/hdlcd_crtc.c b/drivers/gpu/drm/arm/hdlcd_crtc.c
> index c239616f5334..9d683be2e5d3 100644
> --- a/drivers/gpu/drm/arm/hdlcd_crtc.c
> +++ b/drivers/gpu/drm/arm/hdlcd_crtc.c
> @@ -151,15 +151,14 @@ static void hdlcd_crtc_enable(struct drm_crtc *crtc)
>  	clk_prepare_enable(hdlcd->clk);
>  	hdlcd_crtc_mode_set_nofb(crtc);
>  	hdlcd_write(hdlcd, HDLCD_REG_COMMAND, 1);
> +	drm_crtc_vblank_on(crtc);
>  }
>  
>  static void hdlcd_crtc_disable(struct drm_crtc *crtc)
>  {
>  	struct hdlcd_drm_private *hdlcd = crtc_to_hdlcd_priv(crtc);
>  
> -	if (!crtc->state->active)
> -		return;
> -
> +	drm_crtc_vblank_off(crtc);
>  	hdlcd_write(hdlcd, HDLCD_REG_COMMAND, 0);
>  	clk_disable_unprepare(hdlcd->clk);
>  }
> -- 
> 2.7.4
> 
> -- 
> RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
> FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
> according to speedtest.net.

-- 
====================
| I would like to |
| fix the world,  |
| but they're not |
| giving me the   |
 \ source code!  /
  ---------------
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