soc/mediatek: dsi: Increase pcw precision

When configuring MIPI DSI Tx, the value of pcw was calculated from data
rate in MHz, leading to loss of precision. This patch changes to use
data rate in Hz for the calculation so that the resulting value should
be consistent with the one in kernel (CL:1786327).

In addition, change the type of data rate to u32, and calculation of
data rate from pixel clock is changed to use DIV_ROUND_UP for
consistency with kernel (CL:1761843).

Also remove unused variable txdiv.

BRANCH=kukui
BUG=b:149051882
TEST=emerge-jacuzzi coreboot
TEST=No scrolling issue on Juniper AUO and InnoLux panels

Change-Id: I23220d446833b956431006027bbc8cb20fc696a5
Signed-off-by: Yu-Ping Wu <yupingso@chromium.org>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/38827
Reviewed-by: Hung-Te Lin <hungte@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

2 files changed, 23 insertions, 18 deletions

diff --git a/src/soc/mediatek/common/dsi.c b/src/soc/mediatek/common/dsi.c
index 238b1eb47f..9222cb0c4b 100644
--- a/src/soc/mediatek/common/dsi.c
+++ b/src/soc/mediatek/common/dsi.c
@@ -39,29 +39,32 @@ static unsigned int mtk_dsi_get_bits_per_pixel(u32 format)
 	return 24;
 }
 
-static int mtk_dsi_get_data_rate(u32 bits_per_pixel, u32 lanes,
+static u32 mtk_dsi_get_data_rate(u32 bits_per_pixel, u32 lanes,
 				 const struct edid *edid)
 {
 	/* data_rate = pixel_clock * bits_per_pixel * mipi_ratio / lanes
-	 * Note pixel_clock comes in kHz and returned data_rate is in Mbps.
+	 * Note pixel_clock comes in kHz and returned data_rate is in bps.
 	 * mipi_ratio is the clk coefficient to balance the pixel clk in MIPI
 	 * for older platforms which do not have complete implementation in HFP.
 	 * Newer platforms should just set that to 1.0 (100 / 100).
 	 */
-	int data_rate = (u64)edid->mode.pixel_clock * bits_per_pixel *
-			MTK_DSI_MIPI_RATIO_NUMERATOR /
-			(1000 * lanes * MTK_DSI_MIPI_RATIO_DENOMINATOR);
-	printk(BIOS_INFO, "DSI data_rate: %d Mbps\n", data_rate);
-
-	if (data_rate < MTK_DSI_DATA_RATE_MIN_MHZ) {
-		printk(BIOS_ERR, "data rate (%dMbps) must be >=%dMbps. "
-		       "Please check the pixel clock (%u), bits per pixel(%u), "
+	u32 data_rate = DIV_ROUND_UP((u64)edid->mode.pixel_clock *
+				     bits_per_pixel * 1000 *
+				     MTK_DSI_MIPI_RATIO_NUMERATOR,
+				     (u64)lanes *
+				     MTK_DSI_MIPI_RATIO_DENOMINATOR);
+	printk(BIOS_INFO, "DSI data_rate: %u bps\n", data_rate);
+
+	if (data_rate < MTK_DSI_DATA_RATE_MIN_MHZ * MHz) {
+		printk(BIOS_ERR, "data rate (%ubps) must be >= %ubps. "
+		       "Please check the pixel clock (%u), "
+		       "bits per pixel (%u), "
 		       "mipi_ratio (%d%%) and number of lanes (%d)\n",
-		       data_rate, MTK_DSI_DATA_RATE_MIN_MHZ,
+		       data_rate, MTK_DSI_DATA_RATE_MIN_MHZ * MHz,
 		       edid->mode.pixel_clock, bits_per_pixel,
 		       (100 * MTK_DSI_MIPI_RATIO_NUMERATOR /
 			MTK_DSI_MIPI_RATIO_DENOMINATOR), lanes);
-		return -1;
+		return 0;
 	}
 	return data_rate;
 }
@@ -71,12 +74,13 @@ __weak void mtk_dsi_override_phy_timing(struct mtk_phy_timing *timing)
 	/* Do nothing. */
 }
 
-static void mtk_dsi_phy_timing(int data_rate, struct mtk_phy_timing *phy_timing)
+static void mtk_dsi_phy_timing(u32 data_rate, struct mtk_phy_timing *phy_timing)
 {
 	u32 cycle_time, ui;
+	u32 data_rate_mhz = DIV_ROUND_UP(data_rate, MHz);
 
-	ui = 1000 / data_rate + 0x01;
-	cycle_time = 8000 / data_rate + 0x01;
+	ui = 1000 / data_rate_mhz + 0x01;
+	cycle_time = 8000 / data_rate_mhz + 0x01;
 
 	memset(phy_timing, 0, sizeof(*phy_timing));
 
@@ -401,11 +405,11 @@ static void mtk_dsi_reset_dphy(void)
 int mtk_dsi_init(u32 mode_flags, u32 format, u32 lanes, const struct edid *edid,
 		 const u8 *init_commands)
 {
-	int data_rate;
+	u32 data_rate;
 	u32 bits_per_pixel = mtk_dsi_get_bits_per_pixel(format);
 
 	data_rate = mtk_dsi_get_data_rate(bits_per_pixel, lanes, edid);
-	if (data_rate < 0)
+	if (!data_rate)
 		return -1;
 
 	mtk_dsi_configure_mipi_tx(data_rate, lanes);
diff --git a/src/soc/mediatek/common/include/soc/dsi_common.h b/src/soc/mediatek/common/include/soc/dsi_common.h
index 3052689c90..25727b8398 100644
--- a/src/soc/mediatek/common/include/soc/dsi_common.h
+++ b/src/soc/mediatek/common/include/soc/dsi_common.h
@@ -16,6 +16,7 @@
 #ifndef SOC_MEDIATEK_DSI_COMMON_H
 #define SOC_MEDIATEK_DSI_COMMON_H
 
+#include <commonlib/helpers.h>
 #include <edid.h>
 #include <types.h>
 #include <soc/addressmap.h>
@@ -358,7 +359,7 @@ struct lcm_init_command {
 
 /* Functions that each SOC should provide. */
 void mtk_dsi_reset(void);
-void mtk_dsi_configure_mipi_tx(int data_rate, u32 lanes);
+void mtk_dsi_configure_mipi_tx(u32 data_rate, u32 lanes);
 
 /* Functions as weak no-ops that can be overridden. */
 void mtk_dsi_override_phy_timing(struct mtk_phy_timing *timing);