Re: [PATCH 2/6] drm/i915/gen9: Only copy WM results for changed pipes to skl_hw

[Matt Roper <matthew.d.roper@intel.com>]

On Wed, Jul 20, 2016 at 04:59:58PM -0400, Lyude wrote:
> From: Matt Roper <matthew.d.roper@intel.com>
> 
> When we write watermark values to the hardware, those values are stored
> in dev_priv->wm.skl_hw.  However with recent watermark changes, the
> results structure we're copying from only contains valid watermark and
> DDB values for the pipes that are actually changing; the values for
> other pipes remain 0.  Thus a blind copy of the entire skl_wm_values
> structure will clobber the values for unchanged pipes...we need to be
> more selective and only copy over the values for the changing pipes.
> 
> This mistake was hidden until recently due to another bug that caused us
> to erroneously re-calculate watermarks for all active pipes rather than
> changing pipes.  Only when that bug was fixed was the impact of this bug
> discovered (e.g., modesets failing with "Requested display configuration
> exceeds system watermark limitations" messages and leaving watermarks
> non-functional, even ones initiated by intel_fbdev_restore_mode).
> 
> Changes since v1:
>  - Add a function for copying a pipe's wm values
>    (skl_copy_wm_for_pipe()) so we can reuse this later

Your changes look good to me.

Reviewed-by: Matt Roper <matthew.d.roper@intel.com>

> 
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Fixes: 734fa01f3a17 ("drm/i915/gen9: Calculate watermarks during atomic 'check' (v2)")
> Fixes: 9b6130227495 ("drm/i915/gen9: Re-allocate DDB only for changed pipes")
> Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
> Signed-off-by: Lyude <cpaul@redhat.com>
> ---
>  drivers/gpu/drm/i915/intel_pm.c | 28 ++++++++++++++++++++++++++--
>  1 file changed, 26 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index fa86bea..b7d4af1 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -3966,6 +3966,24 @@ skl_compute_ddb(struct drm_atomic_state *state)
>  	return 0;
>  }
>  
> +static void
> +skl_copy_wm_for_pipe(struct skl_wm_values *dst,
> +		     struct skl_wm_values *src,
> +		     enum pipe pipe)
> +{
> +	dst->wm_linetime[pipe] = src->wm_linetime[pipe];
> +	memcpy(dst->plane[pipe], src->plane[pipe],
> +	       sizeof(dst->plane[pipe]));
> +	memcpy(dst->plane_trans[pipe], src->plane_trans[pipe],
> +	       sizeof(dst->plane_trans[pipe]));
> +
> +	dst->ddb.pipe[pipe] = src->ddb.pipe[pipe];
> +	memcpy(dst->ddb.y_plane[pipe], src->ddb.y_plane[pipe],
> +	       sizeof(dst->ddb.y_plane[pipe]));
> +	memcpy(dst->ddb.plane[pipe], src->ddb.plane[pipe],
> +	       sizeof(dst->ddb.plane[pipe]));
> +}
> +
>  static int
>  skl_compute_wm(struct drm_atomic_state *state)
>  {
> @@ -4038,8 +4056,10 @@ static void skl_update_wm(struct drm_crtc *crtc)
>  	struct drm_device *dev = crtc->dev;
>  	struct drm_i915_private *dev_priv = to_i915(dev);
>  	struct skl_wm_values *results = &dev_priv->wm.skl_results;
> +	struct skl_wm_values *hw_vals = &dev_priv->wm.skl_hw;
>  	struct intel_crtc_state *cstate = to_intel_crtc_state(crtc->state);
>  	struct skl_pipe_wm *pipe_wm = &cstate->wm.skl.optimal;
> +	int pipe;
>  
>  	if ((results->dirty_pipes & drm_crtc_mask(crtc)) == 0)
>  		return;
> @@ -4051,8 +4071,12 @@ static void skl_update_wm(struct drm_crtc *crtc)
>  	skl_write_wm_values(dev_priv, results);
>  	skl_flush_wm_values(dev_priv, results);
>  
> -	/* store the new configuration */
> -	dev_priv->wm.skl_hw = *results;
> +	/*
> +	 * Store the new configuration (but only for the pipes that have
> +	 * changed; the other values weren't recomputed).
> +	 */
> +	for_each_pipe_masked(dev_priv, pipe, results->dirty_pipes)
> +		skl_copy_wm_for_pipe(hw_vals, results, pipe);
>  
>  	mutex_unlock(&dev_priv->wm.wm_mutex);
>  }
> -- 
> 2.7.4
> 

-- 
Matt Roper
Graphics Software Engineer
IoTG Platform Enabling & Development
Intel Corporation
(916) 356-2795
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