[PATCH 02/18] drm/i915: Check vblank delay validity

[Ville Syrjala]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

Make sure we have enough vblank for the computed vblank delay.
Supposedly we'd reject things anyway later if this gets violated,
but it seems niver to do some basic sanity checks early just
so we can't be sure the basic relationship vblank_end > vblank_start
always holds.

Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/display/intel_display.c | 31 +++++++++++++++++---
 1 file changed, 27 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
index ff907afa6451..22b5eacda0f0 100644
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -2633,17 +2633,40 @@ static int intel_crtc_vblank_delay(const struct intel_crtc_state *crtc_state)
 	return vblank_delay;
 }
 
-static int intel_crtc_compute_config(struct intel_atomic_state *state,
-				     struct intel_crtc *crtc)
+static int intel_crtc_compute_vblank_delay(struct intel_atomic_state *state,
+					   struct intel_crtc *crtc)
 {
+	struct intel_display *display = to_intel_display(state);
 	struct intel_crtc_state *crtc_state =
 		intel_atomic_get_new_crtc_state(state, crtc);
 	struct drm_display_mode *adjusted_mode =
 		&crtc_state->hw.adjusted_mode;
+	int vblank_delay, max_vblank_delay;
+
+	vblank_delay = intel_crtc_vblank_delay(crtc_state);
+	max_vblank_delay = adjusted_mode->crtc_vblank_end - adjusted_mode->crtc_vblank_start - 1;
+
+	if (vblank_delay > max_vblank_delay) {
+		drm_dbg_kms(display->drm, "[CRTC:%d:%s] vblank delay (%d) exceeds max (%d)\n",
+			    crtc->base.base.id, crtc->base.name, vblank_delay, max_vblank_delay);
+		return -EINVAL;
+	}
+
+	adjusted_mode->crtc_vblank_start += vblank_delay;
+
+	return 0;
+}
+
+static int intel_crtc_compute_config(struct intel_atomic_state *state,
+				     struct intel_crtc *crtc)
+{
+	struct intel_crtc_state *crtc_state =
+		intel_atomic_get_new_crtc_state(state, crtc);
 	int ret;
 
-	adjusted_mode->crtc_vblank_start +=
-		intel_crtc_vblank_delay(crtc_state);
+	ret = intel_crtc_compute_vblank_delay(state, crtc);
+	if (ret)
+		return ret;
 
 	ret = intel_dpll_crtc_compute_clock(state, crtc);
 	if (ret)
-- 
2.45.2