[U-Boot] [PATCH] sunxi: video: HDMI: Fix clock setup

[Jernej Skrabec]

Currently, HDMI driver doesn't consider minimum and maximum allowed rate
of pll3 (video PLL). It works most of the time, but not always.

Consider monitor with resolution 1920x1200, which has pixel clock rate
of 154 MHz. Current code would determine that pll3 rate has to be set to
154 MHz. However, minimum supported rate is 192 MHz. In this case video
output just won't work.

The reason why the driver is written in the way it is, is that at the
time HDMI PHY and clock configuration wasn't fully understood. But now
we have needed knowledge, so the issue can be fixed.

With this fix, clock configuration routine uses full range (1-16) for
clock divider instead of limited one (1, 2, 4, 11). It also considers
minimum and maximum allowed rate for pll3.

Fixes: 56009451d843 ("sunxi: video: Add A64/H3/H5 HDMI driver")
Signed-off-by: Jernej Skrabec <jernej.skrabec at siol.net>
---
Hi!

Unfortunately, issue fixed with patch here has influence on Linux too.
In Linux, minimum and maximum rate is considered only when changing rate.
But because U-Boot already set PLL to "correct" value, Linux clock driver
doesn't see the need to change it. I know that this is Linux driver issue
but let's start at the source of the issue and fix it.

It would be very nice if this can go in 2019.04 release.

Best regards,
Jernej

 drivers/video/sunxi/sunxi_dw_hdmi.c | 62 +++++++++++++++++------------
 1 file changed, 37 insertions(+), 25 deletions(-)

diff --git a/drivers/video/sunxi/sunxi_dw_hdmi.c b/drivers/video/sunxi/sunxi_dw_hdmi.c
index 9dbea649a0..6fe1aa7ee4 100644
--- a/drivers/video/sunxi/sunxi_dw_hdmi.c
+++ b/drivers/video/sunxi/sunxi_dw_hdmi.c
@@ -132,7 +132,7 @@ static int sunxi_dw_hdmi_wait_for_hpd(void)
 	return -1;
 }
 
-static void sunxi_dw_hdmi_phy_set(uint clock)
+static void sunxi_dw_hdmi_phy_set(uint clock, int phy_div)
 {
 	struct sunxi_hdmi_phy * const phy =
 		(struct sunxi_hdmi_phy *)(SUNXI_HDMI_BASE + HDMI_PHY_OFFS);
@@ -146,7 +146,7 @@ static void sunxi_dw_hdmi_phy_set(uint clock)
 	switch (div) {
 	case 1:
 		writel(0x30dc5fc0, &phy->pll);
-		writel(0x800863C0, &phy->clk);
+		writel(0x800863C0 | (phy_div - 1), &phy->clk);
 		mdelay(10);
 		writel(0x00000001, &phy->unk3);
 		setbits_le32(&phy->pll, BIT(25));
@@ -164,7 +164,7 @@ static void sunxi_dw_hdmi_phy_set(uint clock)
 		break;
 	case 2:
 		writel(0x39dc5040, &phy->pll);
-		writel(0x80084381, &phy->clk);
+		writel(0x80084380 | (phy_div - 1), &phy->clk);
 		mdelay(10);
 		writel(0x00000001, &phy->unk3);
 		setbits_le32(&phy->pll, BIT(25));
@@ -178,7 +178,7 @@ static void sunxi_dw_hdmi_phy_set(uint clock)
 		break;
 	case 4:
 		writel(0x39dc5040, &phy->pll);
-		writel(0x80084343, &phy->clk);
+		writel(0x80084340 | (phy_div - 1), &phy->clk);
 		mdelay(10);
 		writel(0x00000001, &phy->unk3);
 		setbits_le32(&phy->pll, BIT(25));
@@ -192,7 +192,7 @@ static void sunxi_dw_hdmi_phy_set(uint clock)
 		break;
 	case 11:
 		writel(0x39dc5040, &phy->pll);
-		writel(0x8008430a, &phy->clk);
+		writel(0x80084300 | (phy_div - 1), &phy->clk);
 		mdelay(10);
 		writel(0x00000001, &phy->unk3);
 		setbits_le32(&phy->pll, BIT(25));
@@ -207,36 +207,46 @@ static void sunxi_dw_hdmi_phy_set(uint clock)
 	}
 }
 
-static void sunxi_dw_hdmi_pll_set(uint clk_khz)
+static void sunxi_dw_hdmi_pll_set(uint clk_khz, int *phy_div)
 {
-	int value, n, m, div = 0, diff;
-	int best_n = 0, best_m = 0, best_diff = 0x0FFFFFFF;
-
-	div = sunxi_dw_hdmi_get_divider(clk_khz * 1000);
+	int value, n, m, div, diff;
+	int best_n = 0, best_m = 0, best_div = 0, best_diff = 0x0FFFFFFF;
 
 	/*
 	 * Find the lowest divider resulting in a matching clock. If there
 	 * is no match, pick the closest lower clock, as monitors tend to
 	 * not sync to higher frequencies.
 	 */
-	for (m = 1; m <= 16; m++) {
-		n = (m * div * clk_khz) / 24000;
-
-		if ((n >= 1) && (n <= 128)) {
-			value = (24000 * n) / m / div;
-			diff = clk_khz - value;
-			if (diff < best_diff) {
-				best_diff = diff;
-				best_m = m;
-				best_n = n;
+	for (div = 1; div <= 16; div++) {
+		int target = clk_khz * div;
+
+		if (target < 192000)
+			continue;
+		if (target > 912000)
+			continue;
+
+		for (m = 1; m <= 16; m++) {
+			n = (m * target) / 24000;
+
+			if (n >= 1 && n <= 128) {
+				value = (24000 * n) / m / div;
+				diff = clk_khz - value;
+				if (diff < best_diff) {
+					best_diff = diff;
+					best_m = m;
+					best_n = n;
+					best_div = div;
+				}
 			}
 		}
 	}
 
+	*phy_div = best_div;
+
 	clock_set_pll3_factors(best_m, best_n);
 	debug("dotclock: %dkHz = %dkHz: (24MHz * %d) / %d / %d\n",
-	      clk_khz, (clock_get_pll3() / 1000) / div,
-	      best_n, best_m, div);
+	      clk_khz, (clock_get_pll3() / 1000) / best_div,
+	      best_n, best_m, best_div);
 }
 
 static void sunxi_dw_hdmi_lcdc_init(int mux, const struct display_timing *edid,
@@ -244,7 +254,7 @@ static void sunxi_dw_hdmi_lcdc_init(int mux, const struct display_timing *edid,
 {
 	struct sunxi_ccm_reg * const ccm =
 		(struct sunxi_ccm_reg *)SUNXI_CCM_BASE;
-	int div = sunxi_dw_hdmi_get_divider(edid->pixelclock.typ);
+	int div = clock_get_pll3() / edid->pixelclock.typ;
 	struct sunxi_lcdc_reg *lcdc;
 
 	if (mux == 0) {
@@ -276,8 +286,10 @@ static void sunxi_dw_hdmi_lcdc_init(int mux, const struct display_timing *edid,
 
 static int sunxi_dw_hdmi_phy_cfg(struct dw_hdmi *hdmi, uint mpixelclock)
 {
-	sunxi_dw_hdmi_pll_set(mpixelclock/1000);
-	sunxi_dw_hdmi_phy_set(mpixelclock);
+	int phy_div;
+
+	sunxi_dw_hdmi_pll_set(mpixelclock / 1000, &phy_div);
+	sunxi_dw_hdmi_phy_set(mpixelclock, phy_div);
 
 	return 0;
 }
-- 
2.21.0