[Intel-gfx] [PATCH v2 15/16] drm/i915/gen9: Reject display updates that exceed wm limitations

[Matt Roper]

If we can't find any valid level 0 watermark values for the requested
atomic transaction, reject the configuration before we try to start
programming the hardware.

Signed-off-by: Matt Roper <matthew.d.roper at intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
---
 drivers/gpu/drm/i915/intel_pm.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 59d4574..96ffd54 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3309,7 +3309,17 @@ static int skl_compute_plane_wm(const struct drm_i915_private *dev_priv,
 
 	if (res_blocks >= ddb_allocation || res_lines > 31) {
 		*enabled = false;
-		return 0;
+
+		/*
+		 * If there are no valid level 0 watermarks, then we can't
+		 * support this display configuration.
+		 */
+		if (level) {
+			return 0;
+		} else {
+			DRM_DEBUG_KMS("Requested display configuration exceeds system watermark limitations\n");
+			return -EINVAL;
+		}
 	}
 
 	*out_blocks = res_blocks;
-- 
2.1.4