From: Darren Etheridge <detheri...@ti.com>

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 <detheri...@ti.com>
Signed-off-by: Sebastian Hesselbarth <sebastian.hesselba...@gmail.com>
---
Changelog:
for v1:
- reword comment

Cc: David Airlie <airl...@linux.ie>
Cc: Darren Etheridge <detheri...@ti.com>
Cc: Rob Clark <robdcl...@gmail.com>
Cc: Russell King <rmk+ker...@arm.linux.org.uk>
Cc: Daniel Vetter <daniel.vet...@ffwll.ch>
Cc: dri-devel@lists.freedesktop.org
Cc: linux-ker...@vger.kernel.org
---
 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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