drm/i915/gen9: Only copy WM results for changed pipes to skl_hw

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

Fixes: 734fa01f ("drm/i915/gen9: Calculate watermarks during atomic 'check' (v2)")
Fixes: 9b613022 ("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>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Cc: stable@vger.kernel.org
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Cc: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1471463761-26796-4-git-send-email-cpaul@redhat.com

drivers/gpu/drm/i915/intel_pm.c

@@ -4117,6 +4117,24 @@ 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)
 {
@@ -4189,8 +4207,10 @@ 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;
@@ -4202,8 +4222,12 @@ 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);
 }