From aa42894471ae6a4e57692f6912690489a1587019 Mon Sep 17 00:00:00 2001 From: Francesco Dolcini Date: Wed, 6 Apr 2022 13:53:25 +0200 Subject: [PATCH] mx6: ddr: Wait before issuing the first MRS cmd Wait 1ms before issuing the first MRS command to write DDR3 Mode registers. There is a requirement to wait a minimum time before issuing command to the DDR3 device, according to the JEDEC standard this time is 500us (after RESET_n is de-asserted until CKE becomes active) + tXPR (Reset CKE Exit time, maximum value 360ns). It seems that for some reason this is not enforced by the MMDC controller. Without this change we experienced random memory initialization failures with about 2% boot failure rate on specific problematic boards, after this change we were able to do more than 10.000 power-cycle without a single failure. Fixes: fe0f7f7842e1 ("mx6: add mmdc configuration for MX6Q/MX6DL") Signed-off-by: Francesco Dolcini Reviewed-by: Marek Vasut Reviewed-by: Fabio Estevam --- arch/arm/mach-imx/mx6/ddr.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/arch/arm/mach-imx/mx6/ddr.c b/arch/arm/mach-imx/mx6/ddr.c index 181df941cf..73a637c42d 100644 --- a/arch/arm/mach-imx/mx6/ddr.c +++ b/arch/arm/mach-imx/mx6/ddr.c @@ -1526,6 +1526,11 @@ void mx6_ddr3_cfg(const struct mx6_ddr_sysinfo *sysinfo, ((sysinfo->ncs == 2) ? 1 : 0) << 30; /* SDE_1 for CS1 */ /* Step 8: Write Mode Registers to Init DDR3 devices */ + mdelay(1); /* Wait before issuing the first MRS command. + * Minimum wait time is (tXPR + 500us), + * with max tXPR value 360ns, and 500us wait required after + * RESET_n is de-asserted. + */ for (cs = 0; cs < sysinfo->ncs; cs++) { /* MR2 */ val = (sysinfo->rtt_wr & 3) << 9 | (ddr3_cfg->SRT & 1) << 7 | -- 2.39.5