From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
The hardware never sees the uv_wm values (apart from
uv_wm.min_ddb_alloc affecting the ddb allocation). Thus there
is no point in comparing uv_wm to determine if we need to
reprogram the watermark registers. So let's check only the
rgb/y watermark in skl_plane_wm_equals(). But let's leave
a comment behind so that the next person reading this doesn't
get as confused as I did when I added this check.
If the ddb allocation ends up changing due to uv_wm
skl_ddb_add_affected_planes() takes care of adding the plane
to the state.
TODO: we should perhaps just eliminate uv_wm from the state
and simply track the min_ddb_alloc for uv instead.
Cc: Matt Roper <matthew.d.roper@xxxxxxxxx>
Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/intel_pm.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 345429e5ad45..39299811b650 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -5400,8 +5400,12 @@ static bool skl_plane_wm_equals(struct drm_i915_private *dev_priv,
int level, max_level = ilk_wm_max_level(dev_priv);
for (level = 0; level <= max_level; level++) {
- if (!skl_wm_level_equals(&wm1->wm[level], &wm2->wm[level]) ||
- !skl_wm_level_equals(&wm1->uv_wm[level], &wm2->uv_wm[level]))
+ /*
+ * We don't check uv_wm as the hardware doesn't actually
+ * use it. It only gets used for calculating the required
+ * ddb allocation.
+ */
+ if (!skl_wm_level_equals(&wm1->wm[level], &wm2->wm[level]))
return false;
}
--
2.24.1
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