From: Darren Etheridge <[email protected]>

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 <[email protected]>
Signed-off-by: Sebastian Hesselbarth <[email protected]>
---
Changelog:
for v1:
- reword comment

Cc: David Airlie <[email protected]>
Cc: Darren Etheridge <[email protected]>
Cc: Rob Clark <[email protected]>
Cc: Russell King <[email protected]>
Cc: Daniel Vetter <[email protected]>
Cc: [email protected]
Cc: [email protected]
---
 drivers/gpu/drm/i2c/tda998x_drv.c |    9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/i2c/tda998x_drv.c 
b/drivers/gpu/drm/i2c/tda998x_drv.c
index 7bf227a..7dc5650 100644
--- a/drivers/gpu/drm/i2c/tda998x_drv.c
+++ b/drivers/gpu/drm/i2c/tda998x_drv.c
@@ -784,6 +784,15 @@ tda998x_encoder_mode_set(struct drm_encoder *encoder,
        n_line       = mode->vtotal;
 
        ref_pix      = 3 + mode->hsync_start - mode->hdisplay;
+
+       /*
+        * 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;
+
        de_pix_s     = mode->htotal - mode->hdisplay;
        de_pix_e     = de_pix_s + mode->hdisplay;
        hs_pix_s     = mode->hsync_start - mode->hdisplay;
-- 
1.7.10.4

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