drm/radeon: Set DESKTOP_HEIGHT register to the framebuffer (not mode) height.

The value of this register is transferred to the V_COUNTER register at the
beginning of vertical blank. V_COUNTER is the reference for VLINE waits and
goes from VIEWPORT_Y_START to VIEWPORT_Y_START+VIEWPORT_HEIGHT during scanout,
so if VIEWPORT_Y_START is not 0, V_COUNTER actually went backwards at the
beginning of vertical blank, and VLINE waits excluding the whole scanout area
could never finish (possibly only if VIEWPORT_Y_START is larger than the length
of vertical blank in scanlines). Setting DESKTOP_HEIGHT to the framebuffer
height should prevent this for any kind of VLINE wait.

Fixes https://bugs.freedesktop.org/show_bug.cgi?id=45329 .

CC: stable@vger.kernel.org
Signed-off-by: Michel Dänzer <michel.daenzer@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/atombios_crtc.c

@@ -1184,7 +1184,7 @@ static int dce4_crtc_do_set_base(struct drm_crtc *crtc,
 	WREG32(EVERGREEN_GRPH_ENABLE + radeon_crtc->crtc_offset, 1);
 
 	WREG32(EVERGREEN_DESKTOP_HEIGHT + radeon_crtc->crtc_offset,
-	       crtc->mode.vdisplay);
+	       target_fb->height);
 	x &= ~3;
 	y &= ~1;
 	WREG32(EVERGREEN_VIEWPORT_START + radeon_crtc->crtc_offset,
@@ -1353,7 +1353,7 @@ static int avivo_crtc_do_set_base(struct drm_crtc *crtc,
 	WREG32(AVIVO_D1GRPH_ENABLE + radeon_crtc->crtc_offset, 1);
 
 	WREG32(AVIVO_D1MODE_DESKTOP_HEIGHT + radeon_crtc->crtc_offset,
-	       crtc->mode.vdisplay);
+	       target_fb->height);
 	x &= ~3;
 	y &= ~1;
 	WREG32(AVIVO_D1MODE_VIEWPORT_START + radeon_crtc->crtc_offset,