[U-Boot] [PATCH] sunxi: H6: DRAM: avoid memcpy() on MMIO registers

[Andre Przywara]

Using memcpy() for MMIO operations is, however tempting, not a good idea:
It depends on the specific implementation of memcpy, also lacks barriers.
In this particular case the first registers were written using 64-bit
writes, and the last register using four separate single-byte writes.
Neither is what we actually want.
We get away with it in this case because of the particular details of
the bus implementation, the DRAM controller IP and the values that we
actually write, but we should not leave a bad example around.

Replace the memcpy with a proper loop using the writel() accessor.

Signed-off-by: Andre Przywara <andre.przywara at arm.com>
---
 arch/arm/mach-sunxi/dram_sun50i_h6.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/arm/mach-sunxi/dram_sun50i_h6.c b/arch/arm/mach-sunxi/dram_sun50i_h6.c
index 5da90a2835..e2f141eb9b 100644
--- a/arch/arm/mach-sunxi/dram_sun50i_h6.c
+++ b/arch/arm/mach-sunxi/dram_sun50i_h6.c
@@ -182,6 +182,7 @@ static void mctl_set_timing_lpddr3(struct dram_para *para)
 			(struct sunxi_mctl_ctl_reg *)SUNXI_DRAM_CTL0_BASE;
 	struct sunxi_mctl_phy_reg * const mctl_phy =
 			(struct sunxi_mctl_phy_reg *)SUNXI_DRAM_PHY0_BASE;
+	int i;
 
 	u8 tccd		= 2;
 	u8 tfaw		= max(ns_to_t(50), 4);
@@ -237,8 +238,9 @@ static void mctl_set_timing_lpddr3(struct dram_para *para)
 	u8 twr2rd	= tcwl + 4 + 1 + twtr;
 	u8 trd2wr	= tcl + 4 + (tcksrea >> 1) - tcwl + 1;
 
-	/* set mode register */
-	memcpy(mctl_phy->mr, mr_lpddr3, sizeof(mr_lpddr3));
+	/* set mode registers */
+	for (i = 0; i < ARRAY_SIZE(mr_lpddr3); i++)
+		writel(mr_lpddr3[i], &mctl_phy->mr[i]);
 
 	/* set DRAM timing */
 	writel((twtp << 24) | (tfaw << 16) | (trasmax << 8) | tras,
-- 
2.14.5