mx6sxsabresd: Update DDR initialization

Use the latest DDR initialization values suggested by the FSL hardware team.

While at it, add some comments for clarification.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>

board/freescale/mx6sxsabresd/imximage.cfg

@@ -30,6 +30,7 @@ BOOT_FROM	sd
  *	value	  value to be stored in the register
  */
 
+/* Enable all clocks */
 DATA 4 0x020c4068 0xffffffff
 DATA 4 0x020c406c 0xffffffff
 DATA 4 0x020c4070 0xffffffff
@@ -39,46 +40,69 @@ DATA 4 0x020c407c 0xffffffff
 DATA 4 0x020c4080 0xffffffff
 DATA 4 0x020c4084 0xffffffff
 
+/* IOMUX - DDR IO Type */
 DATA 4 0x020e0618 0x000c0000
 DATA 4 0x020e05fc 0x00000000
+
+/* Clock */
 DATA 4 0x020e032c 0x00000030
 
-DATA 4 0x020e0300 0x00000030
-DATA 4 0x020e02fc 0x00000030
-DATA 4 0x020e05f4 0x00000030
-DATA 4 0x020e0340 0x00000030
+/* Address */
+DATA 4 0x020e0300 0x00000020
+DATA 4 0x020e02fc 0x00000020
+DATA 4 0x020e05f4 0x00000020
+
+/* Control */
+DATA 4 0x020e0340 0x00000020
 
 DATA 4 0x020e0320 0x00000000
-DATA 4 0x020e0310 0x00000030
-DATA 4 0x020e0314 0x00000030
-DATA 4 0x020e0614 0x00000030
+DATA 4 0x020e0310 0x00000020
+DATA 4 0x020e0314 0x00000020
+DATA 4 0x020e0614 0x00000020
 
+/* Data Strobe */
 DATA 4 0x020e05f8 0x00020000
-DATA 4 0x020e0330 0x00000030
-DATA 4 0x020e0334 0x00000030
-DATA 4 0x020e0338 0x00000030
-DATA 4 0x020e033c 0x00000030
+DATA 4 0x020e0330 0x00000028
+DATA 4 0x020e0334 0x00000028
+DATA 4 0x020e0338 0x00000028
+DATA 4 0x020e033c 0x00000028
+
+/* Data */
 DATA 4 0x020e0608 0x00020000
-DATA 4 0x020e060c 0x00000030
-DATA 4 0x020e0610 0x00000030
-DATA 4 0x020e061c 0x00000030
-DATA 4 0x020e0620 0x00000030
-DATA 4 0x020e02ec 0x00000030
-DATA 4 0x020e02f0 0x00000030
-DATA 4 0x020e02f4 0x00000030
-DATA 4 0x020e02f8 0x00000030
+DATA 4 0x020e060c 0x00000028
+DATA 4 0x020e0610 0x00000028
+DATA 4 0x020e061c 0x00000028
+DATA 4 0x020e0620 0x00000028
+DATA 4 0x020e02ec 0x00000028
+DATA 4 0x020e02f0 0x00000028
+DATA 4 0x020e02f4 0x00000028
+DATA 4 0x020e02f8 0x00000028
+
+/* Calibrations - ZQ */
 DATA 4 0x021b0800 0xa1390003
-DATA 4 0x021b080c 0x00270025
-DATA 4 0x021b0810 0x001B001E
-DATA 4 0x021b083c 0x4144013C
-DATA 4 0x021b0840 0x01300128
-DATA 4 0x021b0848 0x4044464A
-DATA 4 0x021b0850 0x3A383C34
+
+/* Write leveling */
+DATA 4 0x021b080c 0x00290025
+DATA 4 0x021b0810 0x00220022
+
+/* DQS Read Gate */
+DATA 4 0x021b083c 0x41480144
+DATA 4 0x021b0840 0x01340130
+
+/* Read/Write Delay */
+DATA 4 0x021b0848 0x3C3E4244
+DATA 4 0x021b0850 0x34363638
+
+/* Read data bit delay */
 DATA 4 0x021b081c 0x33333333
 DATA 4 0x021b0820 0x33333333
 DATA 4 0x021b0824 0x33333333
 DATA 4 0x021b0828 0x33333333
+
+/* Complete calibration by forced measurement */
 DATA 4 0x021b08b8 0x00000800
+
+/* MMDC init - DDR3, 64-bit mode, only MMDC0 is initiated */
 DATA 4 0x021b0004 0x0002002d
 DATA 4 0x021b0008 0x00333030
 DATA 4 0x021b000c 0x676b52f3
@@ -90,16 +114,19 @@ DATA 4 0x021b002c 0x000026d2
 DATA 4 0x021b0030 0x006b1023
 DATA 4 0x021b0040 0x0000005f
 DATA 4 0x021b0000 0x84190000
+
+/* Initialize MT41K256M16HA-125 - MR2 */
 DATA 4 0x021b001c 0x04008032
+/* MR3 */
 DATA 4 0x021b001c 0x00008033
-DATA 4 0x021b001c 0x00068031
+/* MR1 */
+DATA 4 0x021b001c 0x00048031
+/* MR0 */
 DATA 4 0x021b001c 0x05208030
+/* DDR device ZQ calibration */
 DATA 4 0x021b001c 0x04008040
+
+/* Final DDR setup, before operation start */
 DATA 4 0x021b0020 0x00000800
 DATA 4 0x021b0818 0x00011117
 DATA 4 0x021b001c 0x00000000
-
-DATA 4 0x021b083c 0x41400138
-DATA 4 0x021b0840 0x012C011C
-DATA 4 0x021b0848 0x3C3C4044
-DATA 4 0x021b0850 0x34343638