[Intel-gfx] [PATCH] drm/i915/dsi: let HW maintain HS-TRAIL and CLK_POST

[William Tseng]

This change is to adjust TEOT timing and TCLK-POST timing so DSI
signaling can meet CTS specification.

For clock lane, the measured TEOT may be changed from 142.64 ns to
107.36 ns, which is less than (105 ns+12*UI) and is conformed to
mipi D-PHY v1.2 CTS v1.0.

As to TCLK-POST, it may be changed from 133.44 ns to 178.72 ns, which
is greater than (60 ns+52*UI) and is conformed to the CTS standard.

The computed UI is around 1.47 ns.

Cc: Ville Syrjala <ville.syrjala at linux.intel.com>
Cc: Jani Nikula <jani.nikula at linux.intel.com>
Cc: Vandita Kulkarni <vandita.kulkarni at intel.com>
Cc: Suraj Kandpal <suraj.kandpal at intel.com>
Cc: Lee Shawn C <shawn.c.lee at intel.com>
Signed-off-by: William Tseng <william.tseng at intel.com>
---
 drivers/gpu/drm/i915/display/icl_dsi.c | 31 ++++----------------------
 1 file changed, 4 insertions(+), 27 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/icl_dsi.c b/drivers/gpu/drm/i915/display/icl_dsi.c
index ad6488e9c2b2..4a13f467ca46 100644
--- a/drivers/gpu/drm/i915/display/icl_dsi.c
+++ b/drivers/gpu/drm/i915/display/icl_dsi.c
@@ -1819,10 +1819,10 @@ static void icl_dphy_param_init(struct intel_dsi *intel_dsi)
 	struct intel_connector *connector = intel_dsi->attached_connector;
 	struct mipi_config *mipi_config = connector->panel.vbt.dsi.config;
 	u32 tlpx_ns;
-	u32 prepare_cnt, exit_zero_cnt, clk_zero_cnt, trail_cnt;
-	u32 ths_prepare_ns, tclk_trail_ns;
+	u32 prepare_cnt, exit_zero_cnt, clk_zero_cnt;
+	u32 ths_prepare_ns;
 	u32 hs_zero_cnt;
-	u32 tclk_pre_cnt, tclk_post_cnt;
+	u32 tclk_pre_cnt;
 
 	tlpx_ns = intel_dsi_tlpx_ns(intel_dsi);
 
@@ -1853,14 +1853,6 @@ static void icl_dphy_param_init(struct intel_dsi *intel_dsi)
 		clk_zero_cnt = ICL_CLK_ZERO_CNT_MAX;
 	}
 
-	/* trail cnt in escape clocks*/
-	trail_cnt = DIV_ROUND_UP(tclk_trail_ns, tlpx_ns);
-	if (trail_cnt > ICL_TRAIL_CNT_MAX) {
-		drm_dbg_kms(&dev_priv->drm, "trail_cnt out of range (%d)\n",
-			    trail_cnt);
-		trail_cnt = ICL_TRAIL_CNT_MAX;
-	}
-
 	/* tclk pre count in escape clocks */
 	tclk_pre_cnt = DIV_ROUND_UP(mipi_config->tclk_pre, tlpx_ns);
 	if (tclk_pre_cnt > ICL_TCLK_PRE_CNT_MAX) {
@@ -1869,15 +1861,6 @@ static void icl_dphy_param_init(struct intel_dsi *intel_dsi)
 		tclk_pre_cnt = ICL_TCLK_PRE_CNT_MAX;
 	}
 
-	/* tclk post count in escape clocks */
-	tclk_post_cnt = DIV_ROUND_UP(mipi_config->tclk_post, tlpx_ns);
-	if (tclk_post_cnt > ICL_TCLK_POST_CNT_MAX) {
-		drm_dbg_kms(&dev_priv->drm,
-			    "tclk_post_cnt out of range (%d)\n",
-			    tclk_post_cnt);
-		tclk_post_cnt = ICL_TCLK_POST_CNT_MAX;
-	}
-
 	/* hs zero cnt in escape clocks */
 	hs_zero_cnt = DIV_ROUND_UP(mipi_config->ths_prepare_hszero -
 				   ths_prepare_ns, tlpx_ns);
@@ -1902,19 +1885,13 @@ static void icl_dphy_param_init(struct intel_dsi *intel_dsi)
 			       CLK_ZERO_OVERRIDE |
 			       CLK_ZERO(clk_zero_cnt) |
 			       CLK_PRE_OVERRIDE |
-			       CLK_PRE(tclk_pre_cnt) |
-			       CLK_POST_OVERRIDE |
-			       CLK_POST(tclk_post_cnt) |
-			       CLK_TRAIL_OVERRIDE |
-			       CLK_TRAIL(trail_cnt));
+			       CLK_PRE(tclk_pre_cnt));
 
 	/* data lanes dphy timings */
 	intel_dsi->dphy_data_lane_reg = (HS_PREPARE_OVERRIDE |
 					 HS_PREPARE(prepare_cnt) |
 					 HS_ZERO_OVERRIDE |
 					 HS_ZERO(hs_zero_cnt) |
-					 HS_TRAIL_OVERRIDE |
-					 HS_TRAIL(trail_cnt) |
 					 HS_EXIT_OVERRIDE |
 					 HS_EXIT(exit_zero_cnt));
 
-- 
2.34.1