Re: [PATCH v2 2/2] drm/i915: Ignore transcoder B/C on LPT/WPT FIFO underrun handling

[Daniel Vetter <daniel@ffwll.ch>]

On Thu, Nov 26, 2015 at 10:55:53PM +0200, ville.syrjala@linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> LPT/WPT only have transcoder A, so we shouldn't look at FIFO underruns
> for transocoder B/C. And more importnatnly we should not consider
> the state of underrun reporting for transcoders B/C when checking
> whether we can enable the south error interrupt.
> 
> The whole thing is a bit of mess since we store the underrun reporting
> state for transcoder A under intel_crtc for pipe A, irrespective of
> which pipe may actually be driving the transcoder. But I figured trying
> to change that would result in more churn.
> 
> Caveat: Still untested
> 
> v2: Use HAS_PCH_LPT_H instead of HAS_DDI
>     Use cpt_check_pch_fifo_underruns() on LPT-H/WPT-H too
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

I've battled hsw lpt fifo underrun issues last week and never seen a fifo
underrun on pipe B/C. Have you seen them anywhere really?

If not I think we can skip this patch here, since I think I tracked it all
down.
-Daniel

> ---
>  drivers/gpu/drm/i915/intel_fifo_underrun.c | 27 ++++++++++++++++++++++-----
>  1 file changed, 22 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_fifo_underrun.c b/drivers/gpu/drm/i915/intel_fifo_underrun.c
> index bda526660e20..3d3acc8b8367 100644
> --- a/drivers/gpu/drm/i915/intel_fifo_underrun.c
> +++ b/drivers/gpu/drm/i915/intel_fifo_underrun.c
> @@ -48,6 +48,14 @@
>   * The code also supports underrun detection on the PCH transcoder.
>   */
>  
> +static bool cpt_transcoder_exists(struct drm_i915_private *dev_priv,
> +				  enum transcoder pch_transcoder)
> +{
> +	/* LPT-H/WPT-H have only transcoder A */
> +	return HAS_PCH_CPT(dev_priv) ||
> +		(HAS_PCH_LPT_H(dev_priv) && pch_transcoder == TRANSCODER_A);
> +}
> +
>  static bool ivb_can_enable_err_int(struct drm_device *dev)
>  {
>  	struct drm_i915_private *dev_priv = dev->dev_private;
> @@ -69,13 +77,16 @@ static bool ivb_can_enable_err_int(struct drm_device *dev)
>  static bool cpt_can_enable_serr_int(struct drm_device *dev)
>  {
>  	struct drm_i915_private *dev_priv = dev->dev_private;
> -	enum pipe pipe;
> -	struct intel_crtc *crtc;
> +	enum transcoder pch_transcoder;
>  
>  	assert_spin_locked(&dev_priv->irq_lock);
>  
> -	for_each_pipe(dev_priv, pipe) {
> -		crtc = to_intel_crtc(dev_priv->pipe_to_crtc_mapping[pipe]);
> +	for_each_pipe(dev_priv, pch_transcoder) {
> +		struct intel_crtc *crtc =
> +			to_intel_crtc(dev_priv->pipe_to_crtc_mapping[pch_transcoder]);
> +
> +		if (!cpt_transcoder_exists(dev_priv, pch_transcoder))
> +			continue;
>  
>  		if (crtc->pch_fifo_underrun_disabled)
>  			return false;
> @@ -206,6 +217,9 @@ static void cpt_check_pch_fifo_underruns(struct intel_crtc *crtc)
>  
>  	assert_spin_locked(&dev_priv->irq_lock);
>  
> +	if (!cpt_transcoder_exists(dev_priv, pch_transcoder))
> +		return;
> +
>  	if ((serr_int & SERR_INT_TRANS_FIFO_UNDERRUN(pch_transcoder)) == 0)
>  		return;
>  
> @@ -222,6 +236,9 @@ static void cpt_set_fifo_underrun_reporting(struct drm_device *dev,
>  {
>  	struct drm_i915_private *dev_priv = dev->dev_private;
>  
> +	if (!cpt_transcoder_exists(dev_priv, pch_transcoder))
> +		return;
> +
>  	if (enable) {
>  		I915_WRITE(SERR_INT,
>  			   SERR_INT_TRANS_FIFO_UNDERRUN(pch_transcoder));
> @@ -436,7 +453,7 @@ void intel_check_pch_fifo_underruns(struct drm_i915_private *dev_priv)
>  		if (crtc->pch_fifo_underrun_disabled)
>  			continue;
>  
> -		if (HAS_PCH_CPT(dev_priv))
> +		if (HAS_PCH_CPT(dev_priv) || HAS_PCH_LPT_H(dev_priv))
>  			cpt_check_pch_fifo_underruns(crtc);
>  	}
>  
> -- 
> 2.4.10
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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