[Intel-gfx] [PATCH] drm/i915: More cautious with pch fifo underruns

[Daniel Vetter]

On Mon, Nov 24, 2014 at 05:02:45PM +0100, Daniel Vetter wrote:
> Apparently PCH fifo underruns are tricky, we have plenty reports that
> we see the occasional underrun (especially at boot-up).
> 
> So for a change let's see what happens when we don't re-enable pch
> fifo underrun reporting when the pipe is disabled. This means that the
> kernel can't catch pch fifo underruns when they happen (except when
> all pipes are on on the pch). But we'll still catch underruns when
> disabling the pipe again. So not a terrible reduction in test
> coverage.
> 
> References: https://bugs.freedesktop.org/show_bug.cgi?id=85898
> References: https://bugs.freedesktop.org/show_bug.cgi?id=86233
> References: https://bugs.freedesktop.org/show_bug.cgi?id=86478
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=85898
Tested-by: lu hua <huax.lu at intel.com>

> ---
>  drivers/gpu/drm/i915/intel_display.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 320bf4c78c8c..a4106049e158 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -4501,7 +4501,6 @@ static void ironlake_crtc_disable(struct drm_crtc *crtc)
>  		ironlake_fdi_disable(crtc);
>  
>  		ironlake_disable_pch_transcoder(dev_priv, pipe);
> -		intel_set_pch_fifo_underrun_reporting(dev_priv, pipe, true);
>  
>  		if (HAS_PCH_CPT(dev)) {
>  			/* disable TRANS_DP_CTL */
> @@ -4572,8 +4571,6 @@ static void haswell_crtc_disable(struct drm_crtc *crtc)
>  
>  	if (intel_crtc->config.has_pch_encoder) {
>  		lpt_disable_pch_transcoder(dev_priv);
> -		intel_set_pch_fifo_underrun_reporting(dev_priv, TRANSCODER_A,
> -						      true);
>  		intel_ddi_fdi_disable(crtc);
>  	}
>  
> -- 
> 2.1.1
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch