driver/ddr/fsl: Adjust timing_cfg_0 to better support two DDR slots

Increase write-to-write and read-to-read turnaround time for two-slot DDR
configurations. Previously only quad-rank and two dual-rank configurations
have this additional turnaround time. A recent test on two single-rank
DIMMs shows the shorter additional turnaround time is also needed.

Signed-off-by: York Sun <yorksun@freescale.com>

drivers/ddr/fsl/ctrl_regs.c

@@ -253,22 +253,30 @@ static void set_csn_config_2(int i, fsl_ddr_cfg_regs_t *ddr)
 /* -3E = 667 CL5, -25 = CL6 800, -25E = CL5 800 */
 
 #if !defined(CONFIG_SYS_FSL_DDR1)
+/*
+ * Check DIMM configuration, return 2 if quad-rank or two dual-rank
+ * Return 1 if other two slots configuration. Return 0 if single slot.
+ */
 static inline int avoid_odt_overlap(const dimm_params_t *dimm_params)
 {
 #if CONFIG_DIMM_SLOTS_PER_CTLR == 1
 	if (dimm_params[0].n_ranks == 4)
-		return 1;
+		return 2;
 #endif
 
 #if CONFIG_DIMM_SLOTS_PER_CTLR == 2
 	if ((dimm_params[0].n_ranks == 2) &&
 		(dimm_params[1].n_ranks == 2))
-		return 1;
+		return 2;
 
 #ifdef CONFIG_FSL_DDR_FIRST_SLOT_QUAD_CAPABLE
 	if (dimm_params[0].n_ranks == 4)
-		return 1;
+		return 2;
 #endif
+
+	if ((dimm_params[0].n_ranks != 0) &&
+	    (dimm_params[2].n_ranks != 0))
+		return 1;
 #endif
 	return 0;
 }
@@ -316,6 +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;
+	int odt_overlap;
 	/*
 	 * (tXARD and tXARDS). Empirical?
 	 * The DDR3 spec has not tXARD,
@@ -331,13 +340,23 @@ static void set_timing_cfg_0(fsl_ddr_cfg_regs_t *ddr,
 	/* set the turnaround time */
 
 	/*
-	 * for single quad-rank DIMM and two dual-rank DIMMs
+	 * for single quad-rank DIMM and two-slot DIMMs
 	 * to avoid ODT overlap
 	 */
-	if (avoid_odt_overlap(dimm_params)) {
+	odt_overlap = avoid_odt_overlap(dimm_params);
+	switch (odt_overlap) {
+	case 2:
 		twwt_mclk = 2;
 		trrt_mclk = 1;
+		break;
+	case 1:
+		twwt_mclk = 1;
+		trrt_mclk = 0;
+		break;
+	default:
+		break;
 	}
+
 	/* for faster clock, need more time for data setup */
 	trwt_mclk = (data_rate/1000000 > 1800) ? 2 : 1;
 
@@ -383,7 +402,7 @@ static void set_timing_cfg_0(fsl_ddr_cfg_regs_t *ddr,
 		);
 	debug("FSLDDR: timing_cfg_0 = 0x%08x\n", ddr->timing_cfg_0);
 }
-#endif	/* defined(CONFIG_SYS_FSL_DDR2) */
+#endif	/* !defined(CONFIG_SYS_FSL_DDR1) */
 
 /* DDR SDRAM Timing Configuration 3 (TIMING_CFG_3) */
 static void set_timing_cfg_3(fsl_ddr_cfg_regs_t *ddr,