Some LCD controller cannot provide valid VESA style sync, i.e. coincident
HS/VS edges. First, this patch adds hskew passed from the adjusted_mode to
reference pixel calculation to allow those controllers to add an offset
relative to the expected reference pixel.
Signed-off-by: Darren Etheridge <detheridge@xxxxxx>
Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@xxxxxxxxx>
---
Changelog:
for v1:
- reword comment
Cc: David Airlie <airlied@xxxxxxxx>
Cc: Darren Etheridge <detheridge@xxxxxx>
Cc: Rob Clark <robdclark@xxxxxxxxx>
Cc: Russell King <rmk+kernel@xxxxxxxxxxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
drivers/gpu/drm/i2c/tda998x_drv.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/drivers/gpu/drm/i2c/tda998x_drv.c b/drivers/gpu/drm/i2c/tda998x_drv.c
index 92fcb3d..c2bd711 100644
--- a/drivers/gpu/drm/i2c/tda998x_drv.c
+++ b/drivers/gpu/drm/i2c/tda998x_drv.c
@@ -782,6 +782,14 @@ tda998x_encoder_mode_set(struct drm_encoder *encoder,
de_pix_s = mode->htotal - mode->hdisplay;
ref_pix = 3 + hs_pix_s;
+ /*
+ * Attached LCD controllers may generate broken sync. Allow
+ * those to adjust the position of the rising VS edge by adding
+ * HSKEW to ref_pix.
+ */
+ if (adjusted_mode->flags & DRM_MODE_FLAG_HSKEW)
+ ref_pix += adjusted_mode->hskew;
+
if ((mode->flags & DRM_MODE_FLAG_INTERLACE) == 0) {
ref_line = 1 + mode->vsync_start - mode->vdisplay;
vwin1_line_s = mode->vtotal - mode->vdisplay - 1;
--
1.7.10.4
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