[PATCH 1/6] drm: bridge: samsung-dsim: Support multi-lane calculations

[Adam Ford]

If there is more than one lane, the HFP, HBP, and HSA is calculated in
bytes/pixel, then they are divided amongst the different lanes with some
additional overhead. This is necessary to achieve higher resolutions while
keeping the pixel clocks lower as the number of lanes increase.

Signed-off-by: Adam Ford <aford173 at gmail.com>
---
 drivers/gpu/drm/bridge/samsung-dsim.c | 40 +++++++++++++++++++++++----
 1 file changed, 34 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
index e0a402a85787..1ccbad4ea577 100644
--- a/drivers/gpu/drm/bridge/samsung-dsim.c
+++ b/drivers/gpu/drm/bridge/samsung-dsim.c
@@ -215,6 +215,7 @@
 #define DSI_RX_FIFO_SIZE		256
 #define DSI_XFER_TIMEOUT_MS		100
 #define DSI_RX_FIFO_EMPTY		0x30800002
+#define DSI_HSYNC_PKT_OVERHEAD	6
 
 #define OLD_SCLK_MIPI_CLK_NAME		"pll_clk"
 
@@ -879,13 +880,40 @@ static void samsung_dsim_set_display_mode(struct samsung_dsim *dsi)
 			| DSIM_MAIN_VBP(m->vtotal - m->vsync_end);
 		samsung_dsim_write(dsi, DSIM_MVPORCH_REG, reg);
 
-		reg = DSIM_MAIN_HFP(m->hsync_start - m->hdisplay)
-			| DSIM_MAIN_HBP(m->htotal - m->hsync_end);
-		samsung_dsim_write(dsi, DSIM_MHPORCH_REG, reg);
+		/*
+		 * If there is more than one lane, the HFP, HBP, and HSA
+		 * is calculated in bytes/pixel, then they are divided
+		 * amongst the different lanes with some additional
+		 * overhead correction
+		 */
+		if (dsi->lanes > 1) {
+			u32 hfp, hbp, hsa;
+			int bpp = mipi_dsi_pixel_format_to_bpp(dsi->format) / 8;
+
+			hfp = ((m->hsync_start - m->hdisplay) * bpp) / dsi->lanes;
+			hfp -= (hfp > DSI_HSYNC_PKT_OVERHEAD) ? DSI_HSYNC_PKT_OVERHEAD : 0;
+
+			hbp = ((m->htotal - m->hsync_end) * bpp) / dsi->lanes;
+			hbp -= (hbp > DSI_HSYNC_PKT_OVERHEAD) ? DSI_HSYNC_PKT_OVERHEAD : 0;
 
-		reg = DSIM_MAIN_VSA(m->vsync_end - m->vsync_start)
-			| DSIM_MAIN_HSA(m->hsync_end - m->hsync_start);
-		samsung_dsim_write(dsi, DSIM_MSYNC_REG, reg);
+			hsa = ((m->hsync_end - m->hsync_start) * bpp) / dsi->lanes;
+			hsa -= (hsa > DSI_HSYNC_PKT_OVERHEAD) ? DSI_HSYNC_PKT_OVERHEAD : 0;
+
+			reg = DSIM_MAIN_HFP(hfp) | DSIM_MAIN_HBP(hbp);
+			samsung_dsim_write(dsi, DSIM_MHPORCH_REG, reg);
+
+			reg = DSIM_MAIN_VSA(m->vsync_end - m->vsync_start)
+				| DSIM_MAIN_HSA(hsa);
+			samsung_dsim_write(dsi, DSIM_MSYNC_REG, reg);
+		} else {
+			reg = DSIM_MAIN_HFP(m->hsync_start - m->hdisplay)
+				| DSIM_MAIN_HBP(m->htotal - m->hsync_end);
+			samsung_dsim_write(dsi, DSIM_MHPORCH_REG, reg);
+
+			reg = DSIM_MAIN_VSA(m->vsync_end - m->vsync_start)
+				| DSIM_MAIN_HSA(m->hsync_end - m->hsync_start);
+			samsung_dsim_write(dsi, DSIM_MSYNC_REG, reg);
+		}
 	}
 	reg =  DSIM_MAIN_HRESOL(m->hdisplay, num_bits_resol) |
 		DSIM_MAIN_VRESOL(m->vdisplay, num_bits_resol);
-- 
2.39.2