Overview
  ========
  
  The overall usage pattern for ECC diagnostic commands is the following:
  
    * (injecting errors is initially disabled)
  
    * define inject mask (which tells the DDR controller what type of errors
      we'll be injecting: single/multiple bit etc.)
  
    * enable injecting errors - from now on the controller injects errors as
      indicated in the inject mask
  
  IMPORTANT NOTICE: enabling injecting multiple-bit errors is potentially
  dangerous as such errors are NOT corrected by the controller. Therefore caution
  should be taken when enabling the injection of multiple-bit errors: it is only
  safe when used on a carefully selected memory area and used under control of

  the 'ecc testdw' 'ecc testword' command (see example 'Injecting Multiple-Bit
  Errors' below). In particular, when you simply set the multiple-bit errors in
  inject mask and enable injection, U-Boot is very likely to hang quickly as the
  errors will be injected when it accesses its code, data etc.

  
  
  Use cases for DDR 'ecc' command:
  ================================
  
  Before executing particular tests reset target board or clear status registers:
  
  => ecc captureclear
  => ecc errdetectclr all
  => ecc sbecnt 0
  
  
  Injecting Single-Bit Errors
  ---------------------------
  
  1. Set 1 bit in Data Path Error Inject Mask
  
  => ecc injectdatahi 1
  
  2. Run test over some memory region

  => ecc testdw 200000 10

  
  3. Check ECC status
  
  => ecc status
  ...
  Memory Data Path Error Injection Mask High/Low: 00000001 00000000
  ...
  Memory Single-Bit Error Management (0..255):
    Single-Bit Error Threshold: 255
    Single Bit Error Counter: 16
  ...
  Memory Error Detect:
    Multiple Memory Errors: 0
    Multiple-Bit Error: 0
    Single-Bit Error: 0
  ...
  
  16 errors were generated, Single-Bit Error flag was not set as Single Bit Error
  Counter did not reach  Single-Bit Error Threshold.

  4. Make sure used memory region got re-initialized with 0x0123456789abcdef

  
  => md 200000

  00200000: 01234567 89abcdef 01234567 89abcdef    .#Eg.....#Eg....
  00200010: 01234567 89abcdef 01234567 89abcdef    .#Eg.....#Eg....
  00200020: 01234567 89abcdef 01234567 89abcdef    .#Eg.....#Eg....
  00200030: 01234567 89abcdef 01234567 89abcdef    .#Eg.....#Eg....
  00200040: 01234567 89abcdef 01234567 89abcdef    .#Eg.....#Eg....
  00200050: 01234567 89abcdef 01234567 89abcdef    .#Eg.....#Eg....
  00200060: 01234567 89abcdef 01234567 89abcdef    .#Eg.....#Eg....
  00200070: 01234567 89abcdef 01234567 89abcdef    .#Eg.....#Eg....

  00200080: deadbeef deadbeef deadbeef deadbeef    ................
  00200090: deadbeef deadbeef deadbeef deadbeef    ................

  Injecting Multiple-Bit Errors
  -----------------------------
  
  1. Set more than 1 bit in Data Path Error Inject Mask

  => ecc injectdatahi 1
  => ecc injectdatalo 1

  
  2. Run test over some memory region

  => ecc testword 200000 1

  
  3. Check ECC status
  
  => ecc status
  ...

  Memory Data Path Error Injection Mask High/Low: 00000001 00000001

  ...
  Memory Error Detect:

    Multiple Memory Errors: 0

    Multiple-Bit Error: 1
    Single-Bit Error: 0
  ...

  The Multiple Memory Errors flags not set and Multiple-Bit Error flags are set.

  4. Make sure used memory region got re-initialized with 0x0123456789abcdef

  
  => md 200000

  00200000: 01234567 89abcdef 01234567 89abcdef    .#Eg.....#Eg....
  00200010: 01234567 89abcdef 01234567 89abcdef    .#Eg.....#Eg....
  00200020: 01234567 89abcdef 01234567 89abcdef    .#Eg.....#Eg....
  00200030: 01234567 89abcdef 01234567 89abcdef    .#Eg.....#Eg....
  00200040: 01234567 89abcdef 01234567 89abcdef    .#Eg.....#Eg....
  00200050: 01234567 89abcdef 01234567 89abcdef    .#Eg.....#Eg....
  00200060: 01234567 89abcdef 01234567 89abcdef    .#Eg.....#Eg....
  00200070: 01234567 89abcdef 01234567 89abcdef    .#Eg.....#Eg....

  00200080: deadbeef deadbeef deadbeef deadbeef    ................
  00200090: deadbeef deadbeef deadbeef deadbeef    ................
  
  
  Test Single-Bit Error Counter and Threshold
  -------------------------------------------
  
  1. Set 1 bit in Data Path Error Inject Mask
  
  => ecc injectdatahi 1
  
  2. Enable error injection
  
  => ecc inject en
  
  3. Let u-boot run for a with Single-Bit error injection enabled
  
  4. Disable error injection
  
  => ecc inject dis
  
  4. Check status
  
  => ecc status
  
  ...
  Memory Single-Bit Error Management (0..255):
    Single-Bit Error Threshold: 255

    Single Bit Error Counter: 199

  
  Memory Error Detect:
    Multiple Memory Errors: 1
    Multiple-Bit Error: 0
    Single-Bit Error: 1
  ...
  
  Observe that Single-Bit Error is 'on' which means that Single-Bit Error Counter
  reached Single-Bit Error Threshold. Multiple Memory Errors bit is also 'on', that
  is Counter reached Threshold more than one time (it wraps back after reaching
  Threshold).