drm/bridge: synopsys: dw-mipi-dsi: Set minimum lane byte clock cycles for HSA and HBP

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@nxp.com>
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Robert Foss <rfoss@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230821034008.3876938-7-victor.liu@nxp.com

1 files changed, 13 insertions, 1 deletions

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
index b21ad4ea9dca..2fd01b299f73 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
@@ -759,12 +759,19 @@ 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);
@@ -780,6 +787,11 @@ 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;
 }