[PATCH v8 08/10] drm/sun4i: sun6i_mipi_dsi: Setup burst mode

[Jagan Teki]

Burst mode in DSI would require separate setup initialization
with respect to conventional video mode.

Allwinner DSI controller would need below sequence to setup the
burst mode.
1) configure the burst drq.
2) configure the burst line.
3) finally enable mode.

- To configure burst drq, controller would require to compute the
  edge0, edge1 and fill into burst mode register.

- To configure burst line, controller would require to compute the
  line, sync values and fill into burst line register.

- Enable burst mode, would require to enable burst mode bit in DSI
  control register.

Since there is no direct documentation for these computations
the edge and line formulas are taken from BSP code (from linux-sunxi/
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;

Note: edge0 computation would require tcon0 divider and it's value is
always 4 in Allwinner BSP. This patch find out the divider value at
runtime by reading tcon clocks.

Signed-off-by: Jagan Teki <jagan@xxxxxxxxxxxxxxxxxxxx>
Tested-by: Merlijn Wajer <merlijn@xxxxxxxxxx>
---
 drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 70 ++++++++++++++++++++++++--
 1 file changed, 67 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
index 62b4c822bf18..63b83b47cf0d 100644
--- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
+++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
@@ -356,6 +356,41 @@ static void sun6i_dsi_inst_init(struct sun6i_dsi *dsi,
 		     SUN6I_DSI_INST_JUMP_CFG_NUM(1));
 };
 
+static u32 sun6i_dsi_get_edge1(struct sun6i_dsi *dsi,
+			       struct drm_display_mode *mode, u32 sync_point)
+{
+	struct mipi_dsi_device *device = dsi->device;
+	unsigned int bpp = mipi_dsi_pixel_format_to_bpp(device->format);
+	u32 hact_sync_bp;
+
+	/* Horizontal timings duration excluding front porch */
+	hact_sync_bp = (mode->hdisplay + mode->htotal - mode->hsync_start);
+
+	return (sync_point + ((hact_sync_bp + 20) * bpp / (8 * device->lanes)));
+}
+
+static u32 sun6i_dsi_get_edge0(struct sun6i_dsi *dsi,
+			       struct drm_display_mode *mode, u32 edge1)
+{
+	struct sun4i_tcon *tcon = dsi->tcon;
+	unsigned long dclk_rate, dclk_parent_rate, tcon0_div;
+
+	dclk_rate = clk_get_rate(tcon->dclk);
+	dclk_parent_rate = clk_get_rate(clk_get_parent(tcon->dclk));
+	tcon0_div = dclk_parent_rate / dclk_rate;
+
+	return (edge1 + (mode->hdisplay + 40) * tcon0_div / 8);
+}
+
+static u32 sun6i_dsi_get_line_num(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);
+
+	return (mode->htotal * bpp / (8 * device->lanes));
+}
+
 static int sun6i_dsi_get_drq(struct sun6i_dsi *dsi,
 			      struct drm_display_mode *mode)
 {
@@ -422,8 +457,32 @@ static u16 sun6i_dsi_get_video_start_delay(struct sun6i_dsi *dsi,
 static void sun6i_dsi_setup_burst(struct sun6i_dsi *dsi,
 				  struct drm_display_mode *mode)
 {
-	regmap_write(dsi->regs, SUN6I_DSI_TCON_DRQ_REG,
-		     sun6i_dsi_get_drq(dsi, mode));
+	struct mipi_dsi_device *device = dsi->device;
+	u32 sync_point = 40;
+	u32 line_num = sun6i_dsi_get_line_num(dsi, mode);
+	u32 edge1 = sun6i_dsi_get_edge1(dsi, mode, sync_point);
+	u32 edge0 = sun6i_dsi_get_edge0(dsi, mode, edge1);
+	u32 val;
+
+	if (edge1 > line_num)
+		edge1 = line_num;
+
+	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_BURST_LINE_REG,
+		     SUN6I_DSI_BURST_LINE_NUM(line_num) |
+		     SUN6I_DSI_BURST_LINE_SYNC_POINT(sync_point));
+
+	/* enable burst mode */
+	regmap_read(dsi->regs, SUN6I_DSI_BASIC_CTL_REG, &val);
+	val |= SUN6I_DSI_BASIC_CTL_VIDEO_BURST;
+	regmap_write(dsi->regs, SUN6I_DSI_BASIC_CTL_REG, val);
 }
 
 static void sun6i_dsi_setup_inst_loop(struct sun6i_dsi *dsi,
@@ -708,7 +767,12 @@ static void sun6i_dsi_encoder_enable(struct drm_encoder *encoder)
 		     SUN6I_DSI_BASIC_CTL1_VIDEO_PRECISION |
 		     SUN6I_DSI_BASIC_CTL1_VIDEO_MODE);
 
-	sun6i_dsi_setup_burst(dsi, mode);
+	regmap_write(dsi->regs, SUN6I_DSI_TCON_DRQ_REG,
+		     sun6i_dsi_get_drq(dsi, mode));
+
+	if (device->mode_flags & MIPI_DSI_MODE_VIDEO_BURST)
+		sun6i_dsi_setup_burst(dsi, mode);
+
 	sun6i_dsi_setup_inst_loop(dsi, mode);
 	sun6i_dsi_setup_format(dsi, mode);
 	sun6i_dsi_setup_timings(dsi, mode);
-- 
2.18.0.321.gffc6fa0e3