[PATCH] sunxi: support asymmetric dual rank DRAM on A64/R40

[Nicolas Boulenguez <nicolas@debian.org>]

From: Icenowy Zheng <icenowy@aosc.io>

Previously we have known that R40 has a configuration register for its
rank 1, which allows different configuration than rank 0. Reverse
engineering of newest libdram of A64 from Allwinner shows that A64 has
this register too. It's bit 0 (which enables dual rank in rank 0
configuration register) means a dedicated rank size setup is used for
rank 1.

Now, Pine64 scheduled to use a 3GiB LPDDR3 DRAM chip (which has 2GiB
rank 0 and 1GiB rank 1) on PinePhone, that makes asymmetric dual rank
DRAM support necessary.

Add this support. As we have gained knowledge of asymmetric dual rank,
we can now allow R40 dual rank memory setup to work too.

Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
---
 .../include/asm/arch-sunxi/dram_sunxi_dw.h    |  11 +-
 arch/arm/mach-sunxi/dram_sunxi_dw.c           | 100 +++++++++++++-----
 2 files changed, 84 insertions(+), 27 deletions(-)

diff --git a/arch/arm/include/asm/arch-sunxi/dram_sunxi_dw.h b/arch/arm/include/asm/arch-sunxi/dram_sunxi_dw.h
index a5a7ebde44..e843c14202 100644
--- a/arch/arm/include/asm/arch-sunxi/dram_sunxi_dw.h
+++ b/arch/arm/include/asm/arch-sunxi/dram_sunxi_dw.h
@@ -215,12 +215,17 @@ struct sunxi_mctl_ctl_reg {
 #define NR_OF_BYTE_LANES	(32 / BITS_PER_BYTE)
 /* The eight data lines (DQn) plus DM, DQS and DQSN */
 #define LINES_PER_BYTE_LANE	(BITS_PER_BYTE + 3)
-struct dram_para {
+
+struct rank_para {
 	u16 page_size;
-	u8 bus_full_width;
-	u8 dual_rank;
 	u8 row_bits;
 	u8 bank_bits;
+};
+
+struct dram_para {
+	u8 dual_rank;
+	u8 bus_full_width;
+	struct rank_para ranks[2];
 	const u8 dx_read_delays[NR_OF_BYTE_LANES][LINES_PER_BYTE_LANE];
 	const u8 dx_write_delays[NR_OF_BYTE_LANES][LINES_PER_BYTE_LANE];
 	const u8 ac_delays[31];
diff --git a/arch/arm/mach-sunxi/dram_sunxi_dw.c b/arch/arm/mach-sunxi/dram_sunxi_dw.c
index 85e7a1874e..b679f92e70 100644
--- a/arch/arm/mach-sunxi/dram_sunxi_dw.c
+++ b/arch/arm/mach-sunxi/dram_sunxi_dw.c
@@ -346,18 +346,24 @@ static void mctl_set_cr(uint16_t socid, struct dram_para *para)
 #else
 #error Unsupported DRAM type!
 #endif
-	       (para->bank_bits == 3 ? MCTL_CR_EIGHT_BANKS : MCTL_CR_FOUR_BANKS) |
+	       (para->ranks[0].bank_bits == 3 ? MCTL_CR_EIGHT_BANKS : MCTL_CR_FOUR_BANKS) |
 	       MCTL_CR_BUS_FULL_WIDTH(para->bus_full_width) |
 	       (para->dual_rank ? MCTL_CR_DUAL_RANK : MCTL_CR_SINGLE_RANK) |
-	       MCTL_CR_PAGE_SIZE(para->page_size) |
-	       MCTL_CR_ROW_BITS(para->row_bits), &mctl_com->cr);
+	       MCTL_CR_PAGE_SIZE(para->ranks[0].page_size) |
+	       MCTL_CR_ROW_BITS(para->ranks[0].row_bits), &mctl_com->cr);
 
-	if (socid == SOCID_R40) {
-		if (para->dual_rank)
-			panic("Dual rank memory not supported\n");
+	if (socid == SOCID_A64 || socid == SOCID_R40) {
+		writel((para->ranks[1].bank_bits == 3 ? MCTL_CR_EIGHT_BANKS : MCTL_CR_FOUR_BANKS) |
+		       MCTL_CR_BUS_FULL_WIDTH(para->bus_full_width) |
+		       (para->dual_rank ? MCTL_CR_DUAL_RANK : MCTL_CR_SINGLE_RANK) |
+		       MCTL_CR_PAGE_SIZE(para->ranks[1].page_size) |
+		       MCTL_CR_ROW_BITS(para->ranks[1].row_bits), &mctl_com->cr_r1);
+	}
 
+	if (socid == SOCID_R40) {
 		/* Mux pin to A15 address line for single rank memory. */
-		setbits_le32(&mctl_com->cr_r1, MCTL_CR_R1_MUX_A15);
+		if (!para->dual_rank)
+			setbits_le32(&mctl_com->cr_r1, MCTL_CR_R1_MUX_A15);
 	}
 }
 
@@ -581,35 +587,63 @@ static int mctl_channel_init(uint16_t socid, struct dram_para *para)
 	return 0;
 }
 
-static void mctl_auto_detect_dram_size(uint16_t socid, struct dram_para *para)
+/*
+ * Test if memory at offset offset matches memory at a certain base
+ */
+static bool mctl_mem_matches_base(u32 offset, ulong base)
+{
+	/* Try to write different values to RAM at two addresses */
+	writel(0, base);
+	writel(0xaa55aa55, base + offset);
+	dsb();
+	/* Check if the same value is actually observed when reading back */
+	return readl(base) ==
+	       readl(base + offset);
+}
+
+static void mctl_auto_detect_dram_size_rank(uint16_t socid, struct dram_para *para, ulong base, struct rank_para *rank)
 {
 	/* detect row address bits */
-	para->page_size = 512;
-	para->row_bits = 16;
-	para->bank_bits = 2;
+	rank->page_size = 512;
+	rank->row_bits = 16;
+	rank->bank_bits = 2;
 	mctl_set_cr(socid, para);
 
-	for (para->row_bits = 11; para->row_bits < 16; para->row_bits++)
-		if (mctl_mem_matches((1 << (para->row_bits + para->bank_bits)) * para->page_size))
+	for (rank->row_bits = 11; rank->row_bits < 16; rank->row_bits++)
+		if (mctl_mem_matches_base((1 << (rank->row_bits + rank->bank_bits)) * rank->page_size, base))
 			break;
 
 	/* detect bank address bits */
-	para->bank_bits = 3;
+	rank->bank_bits = 3;
 	mctl_set_cr(socid, para);
 
-	for (para->bank_bits = 2; para->bank_bits < 3; para->bank_bits++)
-		if (mctl_mem_matches((1 << para->bank_bits) * para->page_size))
+	for (rank->bank_bits = 2; rank->bank_bits < 3; rank->bank_bits++)
+		if (mctl_mem_matches_base((1 << rank->bank_bits) * rank->page_size, base))
 			break;
 
 	/* detect page size */
-	para->page_size = 8192;
+	rank->page_size = 8192;
 	mctl_set_cr(socid, para);
 
-	for (para->page_size = 512; para->page_size < 8192; para->page_size *= 2)
-		if (mctl_mem_matches(para->page_size))
+	for (rank->page_size = 512; rank->page_size < 8192; rank->page_size *= 2)
+		if (mctl_mem_matches_base(rank->page_size, base))
 			break;
 }
 
+static unsigned long mctl_calc_rank_size(struct rank_para *rank)
+{
+	return (1UL << (rank->row_bits + rank->bank_bits)) * rank->page_size;
+}
+
+static void mctl_auto_detect_dram_size(uint16_t socid, struct dram_para *para)
+{
+	mctl_auto_detect_dram_size_rank(socid, para, (ulong)CONFIG_SYS_SDRAM_BASE, &para->ranks[0]);
+
+	if ((socid == SOCID_A64 || socid == SOCID_R40) && para->dual_rank) {
+		mctl_auto_detect_dram_size_rank(socid, para, (ulong)CONFIG_SYS_SDRAM_BASE + mctl_calc_rank_size(&para->ranks[0]), &para->ranks[1]);
+	}
+}
+
 /*
  * The actual values used here are taken from Allwinner provided boot0
  * binaries, though they are probably board specific, so would likely benefit
@@ -688,12 +722,23 @@ unsigned long sunxi_dram_init(void)
 	struct sunxi_mctl_ctl_reg * const mctl_ctl =
 			(struct sunxi_mctl_ctl_reg *)SUNXI_DRAM_CTL0_BASE;
 
+	unsigned long size;
+
 	struct dram_para para = {
 		.dual_rank = 1,
 		.bus_full_width = 1,
-		.row_bits = 15,
-		.bank_bits = 3,
-		.page_size = 4096,
+		.ranks = {
+			{
+				.row_bits = 15,
+				.bank_bits = 3,
+				.page_size = 4096,
+			},
+			{
+				.row_bits = 15,
+				.bank_bits = 3,
+				.page_size = 4096,
+			}
+		},
 
 #if defined(CONFIG_MACH_SUN8I_H3)
 		.dx_read_delays  = SUN8I_H3_DX_READ_DELAYS,
@@ -762,6 +807,13 @@ unsigned long sunxi_dram_init(void)
 	mctl_auto_detect_dram_size(socid, &para);
 	mctl_set_cr(socid, &para);
 
-	return (1UL << (para.row_bits + para.bank_bits)) * para.page_size *
-	       (para.dual_rank ? 2 : 1);
+	size = mctl_calc_rank_size(&para.ranks[0]);
+	if (socid == SOCID_A64 || socid == SOCID_R40) {
+		if (para.dual_rank)
+			size += mctl_calc_rank_size(&para.ranks[1]);
+	} else if (para.dual_rank) {
+		size *= 2;
+	}
+
+	return size;
 }
-- 
2.27.0