Setting up burst mode display would require to compute
- Horizontal timing edge values to fill burst drq register
- Line, sync values to fill burst line register

Since there is no direct documentation for these computations
the edge and line formulas are taken from BSP code
(in drivers/video/sunxi/disp2/disp/de/lowlevel_sun50iw1/de_dsi.c)
line_num = panel->lcd_ht*dsi_pixel_bits[panel->lcd_dsi_format]/
          (8*panel->lcd_dsi_lane);
edge1 = sync_point+(panel->lcd_x+panel->lcd_hbp+20)*
        dsi_pixel_bits[panel->lcd_dsi_format] /(8*panel->lcd_dsi_lane);
edge1 = (edge1>line_num)?line_num:edge1;
edge0 = edge1+(panel->lcd_x+40)*tcon_div/8;
edge0 = (edge0>line_num)?(edge0-line_num):1;

Signed-off-by: Jagan Teki <ja...@amarulasolutions.com>
---
 drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 48 +++++++++++++++++++++-----
 1 file changed, 40 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c 
b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
index 4965b2c71e4c..b6c01891df36 100644
--- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
+++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
@@ -375,20 +375,52 @@ static void sun6i_dsi_setup_burst(struct sun6i_dsi *dsi,
                                  struct drm_display_mode *mode)
 {
        struct mipi_dsi_device *device = dsi->device;
+       unsigned int Bpp = mipi_dsi_pixel_format_to_bpp(device->format);
+       u32 line_num, edge0, edge1, hact_sync_bp;
+       u32 sync_point, tcon_div;
        u32 val = 0;
 
-       if ((mode->hsync_start - mode->hdisplay) > 20) {
-               /* Maaaaaagic */
-               u16 drq = (mode->hsync_start - mode->hdisplay) - 20;
+       if (device->mode_flags != MIPI_DSI_MODE_VIDEO_BURST) {
+               if ((mode->hsync_start - mode->hdisplay) > 20) {
+                       /* Maaaaaagic */
+                       u16 drq = (mode->hsync_start - mode->hdisplay) - 20;
 
-               drq *= mipi_dsi_pixel_format_to_bpp(device->format);
-               drq /= 32;
+                       drq *= Bpp;
+                       drq /= 32;
 
-               val = (SUN6I_DSI_TCON_DRQ_ENABLE_MODE |
-                      SUN6I_DSI_TCON_DRQ_SET(drq));
+                       val = (SUN6I_DSI_TCON_DRQ_ENABLE_MODE |
+                              SUN6I_DSI_TCON_DRQ_SET(drq));
+               }
+
+               regmap_write(dsi->regs, SUN6I_DSI_TCON_DRQ_REG, val);
+
+               return;
        }
 
-       regmap_write(dsi->regs, SUN6I_DSI_TCON_DRQ_REG, val);
+       sync_point = 40;
+       tcon_div = 8;   /* FIXME need to retrive the divider from TCON */
+
+       line_num = mode->htotal * Bpp / (8 * device->lanes);
+       /* Horizental timings duration excluding front porch */
+       hact_sync_bp = (mode->hdisplay + mode->htotal - mode->hsync_start);
+       edge1 = sync_point + ((hact_sync_bp + 20) * Bpp / (8 * device->lanes));
+       if (edge1 > line_num)
+               edge1 = line_num;
+
+       edge0 = edge1 + (mode->hdisplay + 40) * tcon_div / 8;
+       if (edge0 > line_num)
+               edge0 -= line_num;
+       else
+               edge0 = 1;
+
+       regmap_write(dsi->regs, SUN6I_DSI_BURST_DRQ_REG,
+                    SUN6I_DSI_BURST_DRQ_EDGE1(edge1) |
+                    SUN6I_DSI_BURST_DRQ_EDGE0(edge0));
+       regmap_write(dsi->regs, SUN6I_DSI_TCON_DRQ_REG,
+                    SUN6I_DSI_TCON_DRQ_ENABLE_MODE);
+       regmap_write(dsi->regs, SUN6I_DSI_BURST_LINE_REG,
+                    SUN6I_DSI_BURST_LINE_NUM(line_num) |
+                    SUN6I_DSI_BURST_LINE_SYNC_POINT(sync_point));
 }
 
 static void sun6i_dsi_setup_inst_loop(struct sun6i_dsi *dsi,
-- 
2.18.0.321.gffc6fa0e3

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