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-rw-r--r--drivers/gpu/drm/i915/intel_display.c9
-rw-r--r--drivers/gpu/drm/i915/intel_sprite.c21
2 files changed, 30 insertions, 0 deletions
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 3cabe52a4e3b..569717a12723 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -12203,6 +12203,15 @@ static void update_scanline_offset(struct intel_crtc *crtc)
* type. For DP ports it behaves like most other platforms, but on HDMI
* there's an extra 1 line difference. So we need to add two instead of
* one to the value.
+ *
+ * On VLV/CHV DSI the scanline counter would appear to increment
+ * approx. 1/3 of a scanline before start of vblank. Unfortunately
+ * that means we can't tell whether we're in vblank or not while
+ * we're on that particular line. We must still set scanline_offset
+ * to 1 so that the vblank timestamps come out correct when we query
+ * the scanline counter from within the vblank interrupt handler.
+ * However if queried just before the start of vblank we'll get an
+ * answer that's slightly in the future.
*/
if (IS_GEN2(dev_priv)) {
const struct drm_display_mode *adjusted_mode = &crtc->config->base.adjusted_mode;
diff --git a/drivers/gpu/drm/i915/intel_sprite.c b/drivers/gpu/drm/i915/intel_sprite.c
index 8c87c717c7cd..e6517edcd16b 100644
--- a/drivers/gpu/drm/i915/intel_sprite.c
+++ b/drivers/gpu/drm/i915/intel_sprite.c
@@ -83,10 +83,13 @@ int intel_usecs_to_scanlines(const struct drm_display_mode *adjusted_mode,
*/
void intel_pipe_update_start(struct intel_crtc *crtc)
{
+ struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
const struct drm_display_mode *adjusted_mode = &crtc->config->base.adjusted_mode;
long timeout = msecs_to_jiffies_timeout(1);
int scanline, min, max, vblank_start;
wait_queue_head_t *wq = drm_crtc_vblank_waitqueue(&crtc->base);
+ bool need_vlv_dsi_wa = (IS_VALLEYVIEW(dev_priv) || IS_CHERRYVIEW(dev_priv)) &&
+ intel_crtc_has_type(crtc->config, INTEL_OUTPUT_DSI);
DEFINE_WAIT(wait);
vblank_start = adjusted_mode->crtc_vblank_start;
@@ -139,6 +142,24 @@ void intel_pipe_update_start(struct intel_crtc *crtc)
drm_crtc_vblank_put(&crtc->base);
+ /*
+ * On VLV/CHV DSI the scanline counter would appear to
+ * increment approx. 1/3 of a scanline before start of vblank.
+ * The registers still get latched at start of vblank however.
+ * This means we must not write any registers on the first
+ * line of vblank (since not the whole line is actually in
+ * vblank). And unfortunately we can't use the interrupt to
+ * wait here since it will fire too soon. We could use the
+ * frame start interrupt instead since it will fire after the
+ * critical scanline, but that would require more changes
+ * in the interrupt code. So for now we'll just do the nasty
+ * thing and poll for the bad scanline to pass us by.
+ *
+ * FIXME figure out if BXT+ DSI suffers from this as well
+ */
+ while (need_vlv_dsi_wa && scanline == vblank_start)
+ scanline = intel_get_crtc_scanline(crtc);
+
crtc->debug.scanline_start = scanline;
crtc->debug.start_vbl_time = ktime_get();
crtc->debug.start_vbl_count = intel_crtc_get_vblank_counter(crtc);