It turns out that the hblk calculation actually follows a similar pattern
than the other packets. Rework a bit the calculation and add a comment.

Signed-off-by: Maxime Ripard <maxime.rip...@bootlin.com>
---
 drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c 
b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
index 8e6392831e9d..e0288e7dc64e 100644
--- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
+++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
@@ -488,9 +488,13 @@ static void sun6i_dsi_setup_timings(struct sun6i_dsi *dsi,
                  (mode->hsync_start - mode->hdisplay) * Bpp - 
HFP_PACKET_OVERHEAD);
 
        /*
-        * hblk seems to be the line + porches length.
+        * The blanking is set using a sync event (4 bytes) and a
+        * blanking packet (4 bytes + payload + 2 bytes). Its minimal
+        * size is therefore 10 bytes.
         */
-       hblk = mode->htotal * Bpp - hsa;
+#define HBLK_PACKET_OVERHEAD   10
+       hblk = max((unsigned int)HBLK_PACKET_OVERHEAD,
+                  (mode->htotal - (mode->hsync_end - mode->hsync_start)) * Bpp 
- HBLK_PACKET_OVERHEAD);
 
        /*
         * And I'm not entirely sure what vblk is about. The driver in
-- 
git-series 0.9.1
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