drm/tegra: dsi: Use proper back-porch for non-sync video mode

In video modes without sync pulses, the horizontal back-porch needs to
include the horizontal sync width.

Signed-off-by: Thierry Reding <treding@nvidia.com>

1 files changed, 7 insertions, 2 deletions

diff --git a/drivers/gpu/drm/tegra/dsi.c b/drivers/gpu/drm/tegra/dsi.c
index ed970f622903..5c489c257555 100644
--- a/drivers/gpu/drm/tegra/dsi.c
+++ b/drivers/gpu/drm/tegra/dsi.c
@@ -548,14 +548,19 @@ static void tegra_dsi_configure(struct tegra_dsi *dsi, unsigned int pipe,
 
                 /* horizontal sync width */
                 hsw = (mode->hsync_end - mode->hsync_start) * mul / div;
-                hsw -= 10;
 
                 /* horizontal back porch */
                 hbp = (mode->htotal - mode->hsync_end) * mul / div;
-                hbp -= 14;
+
+                if ((dsi->flags & MIPI_DSI_MODE_VIDEO_SYNC_PULSE) == 0)
+                        hbp += hsw;
 
                 /* horizontal front porch */
                 hfp = (mode->hsync_start - mode->hdisplay) * mul / div;
+
+                /* subtract packet overhead */
+                hsw -= 10;
+                hbp -= 14;
                 hfp -= 8;
 
                 tegra_dsi_writel(dsi, hsw << 16 | 0, DSI_PKT_LEN_0_1);