drm/i915: Fix scanoutpos calculations for interlaced modes
The scanline counter counts lines in the current field, not the entire
frame. But the crtc_ timings are the values for the entire frame. Divide
the vertical timings by 2 to make them match the scanline counter.
The rounding was carefully chosen to make it do the right thing wrt. the
observed scanline counter and ISR vblank bit behaviour.
Reviewed-by: mario.kleiner.de@gmail.com
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index b6e4a76..eacbb2f9 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -698,6 +698,12 @@
vbl_start = mode->crtc_vblank_start;
vbl_end = mode->crtc_vblank_end;
+ if (mode->flags & DRM_MODE_FLAG_INTERLACE) {
+ vbl_start = DIV_ROUND_UP(vbl_start, 2);
+ vbl_end /= 2;
+ vtotal /= 2;
+ }
+
ret |= DRM_SCANOUTPOS_VALID | DRM_SCANOUTPOS_ACCURATE;
/*