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Diffstat (limited to 'drivers/gpu/drm/i915/intel_display.c')
| -rw-r--r-- | drivers/gpu/drm/i915/intel_display.c | 9 |
1 files changed, 9 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; |