diff options
| author | Paul Gortmaker <paul.gortmaker@windriver.com> | 2011-12-30 23:53:12 -0500 |
|---|---|---|
| committer | Kumar Gala <galak@kernel.crashing.org> | 2012-01-11 13:59:14 -0600 |
| commit | 3e3262bd149e21d0f5a82648218c26f2aa0e15e7 (patch) | |
| tree | 954100513b29dbcea5804303864c74d75ba729b0 /doc | |
| parent | 2a6b3b74d85cff3f9a76edd09a7b2e8e25bb4eb4 (diff) | |
sbc8548: enable support for hardware SPD errata workaround
Existing boards by default have an issue where the LBC SDRAM
SPD EEPROM and the DDR2 SDRAM SPD EEPROM both land at 0x51.
After the hardware modification listed in the README is made,
then the DDR2 SPD EEPROM appears at 0x53. So this implements
a board specific get_spd() by taking advantage of the existing
weak linkage, that 1st tries reading at 0x53 and then if that
fails, it falls back to the old 0x51.
Since the old dependency issue of "SPD implies no LBC SDRAM"
gets removed with the hardware errata fix, remove that restriction
in the code, so both LBC SDRAM and SPD can be selected.
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Diffstat (limited to 'doc')
| -rw-r--r-- | doc/README.sbc8548 | 20 |
1 files changed, 18 insertions, 2 deletions
diff --git a/doc/README.sbc8548 b/doc/README.sbc8548 index f9e2dea57..0f3f5432f 100644 --- a/doc/README.sbc8548 +++ b/doc/README.sbc8548 @@ -71,7 +71,22 @@ EEPROM data to read what memory is installed. There is a hardware errata, which causes the older local bus SDRAM SPD EEPROM to land at the same address as the DDR2 SPD EEPROM, so -that the SPD data can not be read reliably. +that the SPD data can not be read reliably. You can test if your +board has the errata fix by running "i2c probe". If you see 0x53 +as a valid device, it has been fixed. If you only see 0x50, 0x51 +then your board does not have the fix. + +You can also visually inspect the board to see if this hardware +fix has been applied: + + 1) Remove R314 (RES-R0174-033, 1K, 0603). R314 is located on + the back of the PCB behind the DDR SDRAM SODIMM connector. + 2) Solder RES-R0174-033 (1K, 0603) resistor from R314 pin 2 pad + to R313 pin 2. Pin 2 for each resistor is the end of the + resistor closest to the CPU. + +Boards without the mod will have R314 and R313 in parallel, like "||". +After the mod, they will be touching and form an "L" shape. If you want to upgrade to larger RAM size, you can simply enable #define CONFIG_SPD_EEPROM @@ -79,7 +94,8 @@ If you want to upgrade to larger RAM size, you can simply enable in include/configs/sbc8548.h file. (The lines are already there but listed as #undef). -Note that you will have to physically remove the LBC 128MB DIMM +If you did the i2c test, and your board does not have the errata +fix, then you will have to physically remove the LBC 128MB DIMM from the board's socket to resolve the above i2c address overlap issue and allow SPD autodetection of RAM to work. |