drm/radeon: Move the early vblank IRQ fixup to radeon_get_crtc_scanoutpos()

i915 doesn't need this kludge for most platforms. Although we do
appear to need something similar on certain platforms, but we can
be more accurate when we apply the adjustment since we know exactly
why the scanline counter doesn't always quite match the vblank
status.

Also the current code doesn't handle interlaced modes correctly,
and we already deal with interlaced modes in i915 code.

So let's just move the current code to radeon_get_crtc_scanoutpos()
since that's why it was added. For i915 we'll add a more finely
targeted variant.

v2: Fix vpos vs. *vpos bug (Mario)

Reviewed-by: mario.kleiner.de@gmail.com
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

1 files changed, 22 insertions, 0 deletions

diff --git a/drivers/gpu/drm/radeon/radeon_display.c b/drivers/gpu/drm/radeon/radeon_display.c
index 567215b..d680608 100644
--- a/drivers/gpu/drm/radeon/radeon_display.c
+++ b/drivers/gpu/drm/radeon/radeon_display.c
@@ -1775,5 +1775,27 @@ int radeon_get_crtc_scanoutpos(struct drm_device *dev, int crtc, unsigned int fl
 	if (in_vbl)
 		ret |= DRM_SCANOUTPOS_INVBL;
 
+	/* Is vpos outside nominal vblank area, but less than
+	 * 1/100 of a frame height away from start of vblank?
+	 * If so, assume this isn't a massively delayed vblank
+	 * interrupt, but a vblank interrupt that fired a few
+	 * microseconds before true start of vblank. Compensate
+	 * by adding a full frame duration to the final timestamp.
+	 * Happens, e.g., on ATI R500, R600.
+	 *
+	 * We only do this if DRM_CALLED_FROM_VBLIRQ.
+	 */
+	if ((flags & DRM_CALLED_FROM_VBLIRQ) && !in_vbl) {
+		vbl_start = rdev->mode_info.crtcs[crtc]->base.hwmode.crtc_vdisplay;
+		vtotal = rdev->mode_info.crtcs[crtc]->base.hwmode.crtc_vtotal;
+
+		if (vbl_start - *vpos < vtotal / 100) {
+			*vpos -= vtotal;
+
+			/* Signal this correction as "applied". */
+			ret |= 0x8;
+		}
+	}
+
 	return ret;
 }