[PATCH] sunxi: dram: h6: Improve DDR3 config detection

[Jernej Skrabec]

It turns out that in rare cases, current analytical approach to detect
correct DRAM bus width and rank on H6 doesn't work. On some TV boxes
with DDR3, incorrect DRAM configuration triggers write leveling error
which immediately stops initialization process. Exact reason why this
error appears isn't known. However, if correct configuration is used,
initalization works without problem.

In order to fix this issue, simply try another configuration when any
kind of error appears during initialization, not just those related to
rank and bus width.

Tested-by: Thomas Graichen <thomas.graichen at googlemail.com>
Signed-off-by: Jernej Skrabec <jernej.skrabec at siol.net>
---
 arch/arm/mach-sunxi/dram_sun50i_h6.c | 95 +++++++++++++++-------------
 1 file changed, 51 insertions(+), 44 deletions(-)

diff --git a/arch/arm/mach-sunxi/dram_sun50i_h6.c b/arch/arm/mach-sunxi/dram_sun50i_h6.c
index 9e34da474798..1cde6132be2c 100644
--- a/arch/arm/mach-sunxi/dram_sun50i_h6.c
+++ b/arch/arm/mach-sunxi/dram_sun50i_h6.c
@@ -37,9 +37,9 @@
 
 static void mctl_sys_init(struct dram_para *para);
 static void mctl_com_init(struct dram_para *para);
-static void mctl_channel_init(struct dram_para *para);
+static bool mctl_channel_init(struct dram_para *para);
 
-static void mctl_core_init(struct dram_para *para)
+static bool mctl_core_init(struct dram_para *para)
 {
 	mctl_sys_init(para);
 	mctl_com_init(para);
@@ -51,7 +51,7 @@ static void mctl_core_init(struct dram_para *para)
 	default:
 		panic("Unsupported DRAM type!");
 	};
-	mctl_channel_init(para);
+	return mctl_channel_init(para);
 }
 
 /* PHY initialisation */
@@ -411,7 +411,7 @@ static void mctl_bit_delay_set(struct dram_para *para)
 	}
 }
 
-static void mctl_channel_init(struct dram_para *para)
+static bool mctl_channel_init(struct dram_para *para)
 {
 	struct sunxi_mctl_com_reg * const mctl_com =
 			(struct sunxi_mctl_com_reg *)SUNXI_DRAM_COM_BASE;
@@ -528,46 +528,15 @@ static void mctl_channel_init(struct dram_para *para)
 		clrbits_le32(&mctl_phy->dx[i].gcr[3], ~0x3ffff);
 	udelay(10);
 
-	if (readl(&mctl_phy->pgsr[0]) & 0x400000)
-	{
-		/* Check for single rank and optionally half DQ. */
-		if ((readl(&mctl_phy->dx[0].rsr[0]) & 0x3) == 2 &&
-		    (readl(&mctl_phy->dx[1].rsr[0]) & 0x3) == 2) {
-			para->ranks = 1;
-
-			if ((readl(&mctl_phy->dx[2].rsr[0]) & 0x3) != 2 ||
-			    (readl(&mctl_phy->dx[3].rsr[0]) & 0x3) != 2)
-				para->bus_full_width = 0;
-
-			/* Restart DRAM initialization from scratch. */
-			mctl_core_init(para);
-			return;
-		}
-
-		/*
-		 * Check for dual rank and half DQ. NOTE: This combination
-		 * is highly unlikely and was not tested. Condition is the
-		 * same as in libdram, though.
-		 */
-		if ((readl(&mctl_phy->dx[0].rsr[0]) & 0x3) == 0 &&
-		    (readl(&mctl_phy->dx[1].rsr[0]) & 0x3) == 0) {
-			para->bus_full_width = 0;
-
-			/* Restart DRAM initialization from scratch. */
-			mctl_core_init(para);
-			return;
-		}
-
-		panic("This DRAM setup is currently not supported.\n");
-	}
-
 	if (readl(&mctl_phy->pgsr[0]) & 0xff00000) {
 		/* Oops! There's something wrong! */
 		debug("PLL = %x\n", readl(0x3001010));
 		debug("DRAM PHY PGSR0 = %x\n", readl(&mctl_phy->pgsr[0]));
 		for (i = 0; i < 4; i++)
 			debug("DRAM PHY DX%dRSR0 = %x\n", i, readl(&mctl_phy->dx[i].rsr[0]));
-		panic("Error while initializing DRAM PHY!\n");
+		debug("Error while initializing DRAM PHY!\n");
+
+		return false;
 	}
 
 	if (sunxi_dram_is_lpddr(para->type))
@@ -582,13 +551,54 @@ static void mctl_channel_init(struct dram_para *para)
 	writel(0xffffffff, &mctl_com->maer0);
 	writel(0x7ff, &mctl_com->maer1);
 	writel(0xffff, &mctl_com->maer2);
+
+	return true;
+}
+
+static void mctl_auto_detect_rank_width(struct dram_para *para)
+{
+	/* this is minimum size that it's supported */
+	para->cols = 8;
+	para->rows = 13;
+
+	/*
+	 * Strategy here is to test most demanding combination first and least
+	 * demanding last, otherwise HW might not be fully utilized. For
+	 * example, half bus width and rank = 1 combination would also work
+	 * on HW with full bus width and rank = 2, but only 1/4 RAM would be
+	 * visible.
+	 */
+
+	debug("testing 32-bit width, rank = 2\n");
+	para->bus_full_width = 1;
+	para->ranks = 2;
+	if (mctl_core_init(para))
+		return;
+
+	debug("testing 32-bit width, rank = 1\n");
+	para->bus_full_width = 1;
+	para->ranks = 1;
+	if (mctl_core_init(para))
+		return;
+
+	debug("testing 16-bit width, rank = 2\n");
+	para->bus_full_width = 0;
+	para->ranks = 2;
+	if (mctl_core_init(para))
+		return;
+
+	debug("testing 16-bit width, rank = 1\n");
+	para->bus_full_width = 0;
+	para->ranks = 1;
+	if (mctl_core_init(para))
+		return;
+
+	panic("This DRAM setup is currently not supported.\n");
 }
 
 static void mctl_auto_detect_dram_size(struct dram_para *para)
 {
 	/* TODO: non-(LP)DDR3 */
-	/* Detect rank number and half DQ by the code in mctl_channel_init. */
-	mctl_core_init(para);
 
 	/* detect row address bits */
 	para->cols = 8;
@@ -652,10 +662,6 @@ unsigned long sunxi_dram_init(void)
 			(struct sunxi_mctl_com_reg *)SUNXI_DRAM_COM_BASE;
 	struct dram_para para = {
 		.clk = CONFIG_DRAM_CLK,
-		.ranks = 2,
-		.cols = 11,
-		.rows = 14,
-		.bus_full_width = 1,
 #ifdef CONFIG_SUNXI_DRAM_H6_LPDDR3
 		.type = SUNXI_DRAM_TYPE_LPDDR3,
 		.dx_read_delays  = SUN50I_H6_LPDDR3_DX_READ_DELAYS,
@@ -673,6 +679,7 @@ unsigned long sunxi_dram_init(void)
 	setbits_le32(0x7010310, BIT(8));
 	clrbits_le32(0x7010318, 0x3f);
 
+	mctl_auto_detect_rank_width(&para);
 	mctl_auto_detect_dram_size(&para);
 
 	mctl_core_init(&para);
-- 
2.29.2