Table of interleaving modes supported in cpu/8xxx/ddr/
======================================================
  +-------------+---------------------------------------------------------+
  |             |                   Rank Interleaving                     |
  |             +--------+-----------+-----------+------------+-----------+
  |Memory       |        |           |           |    2x2     |    4x1    |
  |Controller   |  None  | 2x1 lower | 2x1 upper | {CS0+CS1}, | {CS0+CS1+ |
  |Interleaving |        | {CS0+CS1} | {CS2+CS3} | {CS2+CS3}  |  CS2+CS3} |
  +-------------+--------+-----------+-----------+------------+-----------+
  |None         |  Yes   | Yes       | Yes       | Yes        | Yes       |
  +-------------+--------+-----------+-----------+------------+-----------+
  |Cacheline    |  Yes   | Yes       | No        | No, Only(*)| Yes       |
  |             |CS0 Only|           |           | {CS0+CS1}  |           |
  +-------------+--------+-----------+-----------+------------+-----------+
  |Page         |  Yes   | Yes       | No        | No, Only(*)| Yes       |
  |             |CS0 Only|           |           | {CS0+CS1}  |           |
  +-------------+--------+-----------+-----------+------------+-----------+
  |Bank         |  Yes   | Yes       | No        | No, Only(*)| Yes       |
  |             |CS0 Only|           |           | {CS0+CS1}  |           |
  +-------------+--------+-----------+-----------+------------+-----------+
  |Superbank    |  No    | Yes       | No        | No, Only(*)| Yes       |
  |             |        |           |           | {CS0+CS1}  |           |
  +-------------+--------+-----------+-----------+------------+-----------+
 (*) Although the hardware can be configured with memory controller
 interleaving using "2x2" rank interleaving, it only interleaves {CS0+CS1}
 from each controller. {CS2+CS3} on each controller are only rank
 interleaved on that controller.

 For memory controller interleaving, identical DIMMs are suggested. Software
 doesn't check the size or organization of interleaved DIMMs.

The ways to configure the ddr interleaving mode
==============================================
1. In board header file(e.g.MPC8572DS.h), add default interleaving setting
   under "CONFIG_EXTRA_ENV_SETTINGS", like:
	#define CONFIG_EXTRA_ENV_SETTINGS				\
	 "hwconfig=fsl_ddr:ctlr_intlv=bank"			\
	 ......

2. Run u-boot "setenv" command to configure the memory interleaving mode.
   Either numerical or string value is accepted.

  # disable memory controller interleaving
  setenv hwconfig "fsl_ddr:ctlr_intlv=null"

  # cacheline interleaving
  setenv hwconfig "fsl_ddr:ctlr_intlv=cacheline"

  # page interleaving
  setenv hwconfig "fsl_ddr:ctlr_intlv=page"

  # bank interleaving
  setenv hwconfig "fsl_ddr:ctlr_intlv=bank"

  # superbank
  setenv hwconfig "fsl_ddr:ctlr_intlv=superbank"

  # disable bank (chip-select) interleaving
  setenv hwconfig "fsl_ddr:bank_intlv=null"

  # bank(chip-select) interleaving cs0+cs1
  setenv hwconfig "fsl_ddr:bank_intlv=cs0_cs1"

  # bank(chip-select) interleaving cs2+cs3
  setenv hwconfig "fsl_ddr:bank_intlv=cs2_cs3"

  # bank(chip-select) interleaving (cs0+cs1) and (cs2+cs3)  (2x2)
  setenv hwconfig "fsl_ddr:bank_intlv=cs0_cs1_and_cs2_cs3"

  # bank(chip-select) interleaving (cs0+cs1+cs2+cs3) (4x1)
  setenv hwconfig "fsl_ddr:bank_intlv=cs0_cs1_cs2_cs3"

Memory controller address hashing
==================================
If the DDR controller supports address hashing, it can be enabled by hwconfig.

Syntax is:
hwconfig=fsl_ddr:addr_hash=true

Memory controller ECC on/off
============================
If ECC is enabled in board configuratoin file, i.e. #define CONFIG_DDR_ECC,
ECC can be turned on/off by hwconfig.

Syntax is
hwconfig=fsl_ddr:ecc=off

Memory testing options for mpc85xx
==================================
1. Memory test can be done once U-boot prompt comes up using mtest, or
2. Memory test can be done with Power-On-Self-Test function, activated at
   compile time.

   In order to enable the POST memory test, CONFIG_POST needs to be
   defined in board configuraiton header file. By default, POST memory test
   performs a fast test. A slow test can be enabled by changing the flag at
   compiling time. To test memory bigger than 2GB, 36BIT support is needed.
   Memory is tested within a 2GB window. TLBs are used to map the virtual 2GB
   window to physical address so that all physical memory can be tested.

Combination of hwconfig
=======================
Hwconfig can be combined with multiple parameters, for example, on a supported
platform

hwconfig=fsl_ddr:addr_hash=true,ctlr_intlv=cacheline,bank_intlv=cs0_cs1_cs2_cs3,ecc=on

Table for dynamic ODT for DDR3
==============================
For single-slot system with quad-rank DIMM and dual-slot system, dynamic ODT may
be needed, depending on the configuration. The numbers in the following tables are
in Ohms.

* denotes dynamic ODT

Two slots system
+-----------------------+----------+---------------+-----------------------------+-----------------------------+
|     Configuration     |          |DRAM controller|           Slot 1            |            Slot 2           |
+-----------+-----------+----------+-------+-------+--------------+--------------+--------------+--------------+
|           |           |          |       |       |     Rank 1   |     Rank 2   |   Rank 1     |    Rank 2    |
+  Slot 1   |   Slot 2  |Write/Read| Write | Read  |-------+------+-------+------+-------+------+-------+------+
|           |           |          |       |       | Write | Read | Write | Read | Write | Read | Write | Read |
+-----------+-----------+----------+-------+-------+-------+------+-------+------+-------+------+-------+------+
|           |           |  Slot 1  |  off  | 75    | 120   | off  | off   | off  | off   | off  | 30    | 30   |
| Dual Rank | Dual Rank |----------+-------+-------+-------+------+-------+------+-------+------+-------+------+
|           |           |  Slot 2  |  off  | 75    | off   | off  | 30    | 30   | 120   | off  | off   | off  |
+-----------+-----------+----------+-------+-------+-------+------+-------+------+-------+------+-------+------+
|           |           |  Slot 1  |  off  | 75    | 120   | off  | off   | off  | 20    | 20   |       |      |
| Dual Rank |Single Rank|----------+-------+-------+-------+------+-------+------+-------+------+-------+------+
|           |           |  Slot 2  |  off  | 75    | off   | off  | 20    | 20   | 120  *| off  |       |      |
+-----------+-----------+----------+-------+-------+-------+------+-------+------+-------+------+-------+------+
|           |           |  Slot 1  |  off  | 75    | 120  *| off  |       |      | off   | off  | 20    | 20   |
|Single Rank| Dual Rank |----------+-------+-------+-------+------+-------+------+-------+------+-------+------+
|           |           |  Slot 2  |  off  | 75    | 20    | 20   |       |      | 120   | off  | off   | off  |
+-----------+-----------+----------+-------+-------+-------+------+-------+------+-------+------+-------+------+
|           |           |  Slot 1  |  off  | 75    | 120  *| off  |       |      | 30    | 30   |       |      |
|Single Rank|Single Rank|----------+-------+-------+-------+------+-------+------+-------+------+-------+------+
|           |           |  Slot 2  |  off  | 75    | 30    | 30   |       |      | 120  *| off  |       |      |
+-----------+-----------+----------+-------+-------+-------+------+-------+------+-------+------+-------+------+
| Dual Rank |   Empty   |  Slot 1  |  off  | 75    | 40    | off  | off   | off  |       |      |       |      |
+-----------+-----------+----------+-------+-------+-------+------+-------+------+-------+------+-------+------+
|   Empty   | Dual Rank |  Slot 2  |  off  | 75    |       |      |       |      | 40    | off  | off   | off  |
+-----------+-----------+----------+-------+-------+-------+------+-------+------+-------+------+-------+------+
|Single Rank|   Empty   |  Slot 1  |  off  | 75    | 40    | off  |       |      |       |      |       |      |
+-----------+-----------+----------+-------+-------+-------+------+-------+------+-------+------+-------+------+
|   Empty   |Single Rank|  Slot 2  |  off  | 75    |       |      |       |      | 40    | off  |       |      |
+-----------+-----------+----------+-------+-------+-------+------+-------+------+-------+------+-------+------+

Single slot system
+-------------+------------+---------------+-----------------------------+-----------------------------+
|             |            |DRAM controller|     Rank 1   |    Rank 2    |    Rank 3    |    Rank 4    |
|Configuration| Write/Read |-------+-------+-------+------+-------+------+-------+------+-------+------+
|             |            | Write | Read  | Write | Read | Write | Read | Write | Read | Write | Read |
+-------------+------------+-------+-------+-------+------+-------+------+-------+------+-------+------+
|             |   R1       | off   | 75    | 120  *| off  | off   | off  | 20    | 20   | off   | off  |
|             |------------+-------+-------+-------+------+-------+------+-------+------+-------+------+
|             |   R2       | off   | 75    | off   | 20   | 120   | off  | 20    | 20   | off   | off  |
|  Quad Rank  |------------+-------+-------+-------+------+-------+------+-------+------+-------+------+
|             |   R3       | off   | 75    | 20    | 20   | off   | off  | 120  *| off  | off   | off  |
|             |------------+-------+-------+-------+------+-------+------+-------+------+-------+------+
|             |   R4       | off   | 75    | 20    | 20   | off   | off  | off   | 20   | 120   | off  |
+-------------+------------+-------+-------+-------+------+-------+------+-------+------+-------+------+
|             |   R1       | off   | 75    | 40    | off  | off   | off  |
|  Dual Rank  |------------+-------+-------+-------+------+-------+------+
|             |   R2       | off   | 75    | 40    | off  | off   | off  |
+-------------+------------+-------+-------+-------+------+-------+------+
| Single Rank |   R1       | off   | 75    | 40    | off  |
+-------------+------------+-------+-------+-------+------+

Reference http://www.xrosstalkmag.com/mag_issues/xrosstalk_oct08_final.pdf
          http://download.micron.com/pdf/technotes/ddr3/tn4108_ddr3_design_guide.pdf