[U-Boot] [PATCH v2 1/7] sunxi: H6: DRAM: avoid memcpy() on MMIO registers

Andre Przywara
2019-07-02T09:51:42Z

Using memcpy() 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.

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

Signed-off-by: Andre Przywara <andre.przywara@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,
--
2.17.1