83xx: Fix some bugs in spd sdram code

1. RD_TO_PRE missed to add the AL, and need min 2 clocks for
  tRTP according to DDR2 JEDEC spec.
2. WRTORD - tWTR need min 2 clocks according to DDR2 JEDEC spec.
3. add the support of DDR2-533,667,800 DIMMs
4. cpo
5. make the AL to min to gain better performance.

The Micron MT9HTF6472CHY-667D1 DIMMs test passed on
MPC837xEMDS platform at 266MHz/333MHz/400MHz data rate.

items 1, 2 and 5:
Acked-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>

Reported-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
Signed-off-by: Dave Liu <daveliu@freescale.com>
Signed-off-by: Kim Phillips <kim.phillips@freescale.com>

cpu/mpc83xx/spd_sdram.c

@@ -319,7 +319,20 @@ long int spd_sdram()
 	ddrc_clk = gd->mem_clk / 1000000;
 	effective_data_rate = 0;
 
-	if (max_data_rate >= 390 && max_data_rate < 460) { /* it is DDR 400 */
+	if (max_data_rate >= 460) { /* it is DDR2-800, 667, 533 */
+		if (spd.cas_lat & 0x08)
+			caslat = 3;
+		else
+			caslat = 4;
+		if (ddrc_clk <= 460 && ddrc_clk > 350)
+			effective_data_rate = 400;
+		else if (ddrc_clk <=350 && ddrc_clk > 280)
+			effective_data_rate = 333;
+		else if (ddrc_clk <= 280 && ddrc_clk > 230)
+			effective_data_rate = 266;
+		else
+			effective_data_rate = 200;
+	} else if (max_data_rate >= 390 && max_data_rate < 460) { /* it is DDR 400 */
 		if (ddrc_clk <= 460 && ddrc_clk > 350) {
 			/* DDR controller clk at 350~460 */
 			effective_data_rate = 400; /* 5ns */
@@ -466,6 +479,8 @@ long int spd_sdram()
 	} else {
 		twr_clk = picos_to_clk(spd.twr * 250);
 		twtr_clk = picos_to_clk(spd.twtr * 250);
+		if (twtr_clk < 2)
+			twtr_clk = 2;
 	}
 
 	/*
@@ -529,7 +544,7 @@ long int spd_sdram()
 	if (spd.mem_type == SPD_MEMTYPE_DDR2
 	    && (odt_wr_cfg || odt_rd_cfg)
 	    && (caslat < 4)) {
-		add_lat = trcd_clk - 1;
+		add_lat = 4 - caslat;
 		if ((add_lat + caslat) < 4) {
 			add_lat = 0;
 		}
@@ -566,6 +581,9 @@ long int spd_sdram()
 
 		/* Convert SPD value from quarter nanos to picos. */
 		trtp_clk = picos_to_clk(spd.trtp * 250);
+		if (trtp_clk < 2)
+			trtp_clk = 2;
+		trtp_clk += add_lat;
 
 		cke_min_clk = 3;	/* By the book. */
 		four_act = picos_to_clk(37500);	/* By the book. 1k pages? */
@@ -579,7 +597,9 @@ long int spd_sdram()
 	if (spd.mem_type == SPD_MEMTYPE_DDR2) {
 		if (effective_data_rate == 266) {
 			cpo = 0x4;		/* READ_LAT + 1/2 */
-		} else if (effective_data_rate == 333 || effective_data_rate == 400) {
+		} else if (effective_data_rate == 333) {
+			cpo = 0x6;		/* READ_LAT + 1 */
+		} else if (effective_data_rate == 400) {
 			cpo = 0x7;		/* READ_LAT + 5/4 */
 		} else {
 			/* Automatic calibration */