[U-Boot] [Patch v3] driver/ddr/fsl: Fix MRC_CYC calculation for DDR3

[York Sun]

For DDR controller version 4.7 or newer, MRC_CYC (mode register set
cycle time) is max(tMRD, tMOD). tMRD is 4nCK, or 8nCK (RDIMM). tMOD
is max(12nCK, 15ns) according to JEDEC spec.

DDR4 is not affected by this change.

Signed-off-by: York Sun <yorksun at freescale.com>
---
Change log
 v3: Add cast for using max()
 v2: Apply the change only to DDR controller newer than v4.7
     Older DDRC needs to take into account of RDIMM for tMRD

 drivers/ddr/fsl/ctrl_regs.c |   21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/drivers/ddr/fsl/ctrl_regs.c b/drivers/ddr/fsl/ctrl_regs.c
index fe8aa98..03d7ff1 100644
--- a/drivers/ddr/fsl/ctrl_regs.c
+++ b/drivers/ddr/fsl/ctrl_regs.c
@@ -324,6 +324,7 @@ static void set_timing_cfg_0(fsl_ddr_cfg_regs_t *ddr,
 #elif defined(CONFIG_SYS_FSL_DDR3)
 	unsigned int data_rate = get_ddr_freq(0);
 	int txp;
+	unsigned int ip_rev;
 	int odt_overlap;
 	/*
 	 * (tXARD and tXARDS). Empirical?
@@ -336,7 +337,25 @@ static void set_timing_cfg_0(fsl_ddr_cfg_regs_t *ddr,
 	 */
 	txp = max((int)mclk_ps * 3, (mclk_ps > 1540 ? 7500 : 6000));
 
-	tmrd_mclk = 4;
+	ip_rev = fsl_ddr_get_version();
+	if (ip_rev >= 0x40700) {
+		/*
+		 * MRS_CYC = max(tMRD, tMOD)
+		 * tMRD = 4nCK (8nCK for RDIMM)
+		 * tMOD = max(12nCK, 15ns)
+		 */
+		tmrd_mclk = max((unsigned int)12, picos_to_mclk(15000));
+	} else {
+		/*
+		 * MRS_CYC = tMRD
+		 * tMRD = 4nCK (8nCK for RDIMM)
+		 */
+		if (popts->registered_dimm_en)
+			tmrd_mclk = 8;
+		else
+			tmrd_mclk = 4;
+	}
+
 	/* set the turnaround time */
 
 	/*
-- 
1.7.9.5