The current DDR write level calibration routine always overwrite the ralat/walat fields to their maximum value, just save the existing values at the beginning of the calibration routine and restore it at the end.
In case the delay is estimated by the user to be more than one cycle the walat should be configured according to that, this is not automatically done. From the i.MX6 RM:
The user should read the results of the associated delay-line at MPWLDECTRL#[WL_DL_ABS_OFFSET#] and in case the user estimates that the reasonable delay may be above 1 cycle then the user should indicate it at MPWLDECTRL#[WL_CYC_DEL#]. Moreover the user should indicate it in MDMISC[WALAT] field. For example, if the result of the write leveling calibration is 100/256 parts of a cycle, but the user estimates that the delay is above 2 cycles then MPWLDECTRL#[WL_CYC_DEL#] should be configured to 2, so the total delay will be 2 and 100/256 parts of a cycle
Probably it would just possible to not overwrite the mdmisc register in the first place, since this is not present in the write_level_calib() example in NXP AN4467 [1] nor in the i.MX6 RM (44.11.6.1 Hardware Write Leveling Calibration).
Fixes: d339f16911c7 ("arm: imx6: Add DDR3 calibration code for MX6 Q/D/DL") Signed-off-by: Francesco Dolcini francesco.dolcini@toradex.com --- arch/arm/mach-imx/mx6/ddr.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/arch/arm/mach-imx/mx6/ddr.c b/arch/arm/mach-imx/mx6/ddr.c index f872bfdab315..08e2f0f130a6 100644 --- a/arch/arm/mach-imx/mx6/ddr.c +++ b/arch/arm/mach-imx/mx6/ddr.c @@ -108,7 +108,7 @@ int mmdc_do_write_level_calibration(struct mx6_ddr_sysinfo const *sysinfo) { struct mmdc_p_regs *mmdc0 = (struct mmdc_p_regs *)MMDC_P0_BASE_ADDR; struct mmdc_p_regs *mmdc1 = (struct mmdc_p_regs *)MMDC_P1_BASE_ADDR; - u32 esdmisc_val, zq_val; + u32 esdmisc_val, zq_val, mdmisc_val; u32 errors = 0; u32 ldectrl[4] = {0}; u32 ddr_mr1 = 0x4; @@ -131,6 +131,9 @@ int mmdc_do_write_level_calibration(struct mx6_ddr_sysinfo const *sysinfo) /* disable Adopt power down timer */ setbits_le32(&mmdc0->mapsr, 0x1);
+ /* Save old RALAT and WALAT values */ + mdmisc_val = readl(&mmdc0->mdmisc); + debug("Starting write leveling calibration.\n");
/* @@ -217,6 +220,9 @@ int mmdc_do_write_level_calibration(struct mx6_ddr_sysinfo const *sysinfo) writel(esdmisc_val, &mmdc0->mdref); writel(zq_val, &mmdc0->mpzqhwctrl);
+ /* restore walat/ralat */ + writel(mdmisc_val, &mmdc0->mdmisc); + debug("\tMMDC_MPWLDECTRL0 after write level cal: 0x%08x\n", readl(&mmdc0->mpwldectrl0)); debug("\tMMDC_MPWLDECTRL1 after write level cal: 0x%08x\n",