[PATCH v3 6/9] drm/bridge: synopsys: dw-mipi-dsi: Set minimum lane byte clock cycles for HSA and HBP

[Liu Ying]

According to Synopsys support channel, each region of HSA, HBP and HFP must
have minimum number of 10 bytes where constant 4 bytes are for HSS or HSE
and 6 bytes are for blanking packet(header + CRC).  Hence, the below table
comes in.

+------------+----------+-------+
| data lanes | min lbcc | bytes |
+------------+----------+-------+
|     1      |    10    |  1*10 |
+------------+----------+-------+
|     2      |    5     |  2*5  |
+------------+----------+-------+
|     3      |    4     |  3*4  |
+------------+----------+-------+
|     4      |    3     |  4*3  |
+------------+----------+-------+

Implement the minimum lbcc numbers to make sure that the values programmed
into DSI_VID_HSA_TIME and DSI_VID_HBP_TIME registers meet the minimum
number requirement.  For DSI_VID_HLINE_TIME register, it seems that the
value programmed should be based on mode->htotal as-is, instead of sum up
HSA, HBP, HFP and HDISPLAY.

This helps the case where Raydium RM67191 DSI panel is connected, since
it's video timing for hsync length is only 2 pixels and without this patch
the programmed value for DSI_VID_HSA_TIME is only 2 with 4 data lanes.

Signed-off-by: Liu Ying <victor.liu at nxp.com>
Reviewed-by: Neil Armstrong <neil.armstrong at linaro.org>
---
v2->v3:
* Add Neil's R-b tag from v1.

v1->v2:
* No change.

 drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
index 332388fd86da..536306ccea5a 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
@@ -757,12 +757,19 @@ static void dw_mipi_dsi_command_mode_config(struct dw_mipi_dsi *dsi)
 	dsi_write(dsi, DSI_MODE_CFG, ENABLE_CMD_MODE);
 }
 
+static const u32 minimum_lbccs[] = {10, 5, 4, 3};
+
+static inline u32 dw_mipi_dsi_get_minimum_lbcc(struct dw_mipi_dsi *dsi)
+{
+	return minimum_lbccs[dsi->lanes - 1];
+}
+
 /* Get lane byte clock cycles. */
 static u32 dw_mipi_dsi_get_hcomponent_lbcc(struct dw_mipi_dsi *dsi,
 					   const struct drm_display_mode *mode,
 					   u32 hcomponent)
 {
-	u32 frac, lbcc;
+	u32 frac, lbcc, minimum_lbcc;
 	int bpp;
 
 	bpp = mipi_dsi_pixel_format_to_bpp(dsi->format);
@@ -778,6 +785,11 @@ static u32 dw_mipi_dsi_get_hcomponent_lbcc(struct dw_mipi_dsi *dsi,
 	if (frac)
 		lbcc++;
 
+	minimum_lbcc = dw_mipi_dsi_get_minimum_lbcc(dsi);
+
+	if (lbcc < minimum_lbcc)
+		lbcc = minimum_lbcc;
+
 	return lbcc;
 }
 
-- 
2.37.1