diff options
| author | Paul Gortmaker <paul.gortmaker@windriver.com> | 2011-12-30 23:53:10 -0500 |
|---|---|---|
| committer | Kumar Gala <galak@kernel.crashing.org> | 2012-01-11 13:59:07 -0600 |
| commit | 7e44f2b710db09a1b02e55246e0915732cc4775e (patch) | |
| tree | e94b2b4fa41c941841bcb5b61214e3b9b82f12d3 /doc | |
| parent | 5f4c6f0db930646e9ca3b479b5fe9b8d2691fa77 (diff) | |
sbc8548: Make enabling SPD RAM configuration work
Previously, SPD configuration of RAM was non functional on
this board. Now that the root cause is known (an i2c address
conflict), there is a simple end-user workaround - remove the
old slower local bus 128MB module and then SPD detection on the
main DDR2 memory module works fine.
We make the enablement of the LBC SDRAM support conditional on
being not SPD enabled. We can revisit this dependency as the
hardware workaround becomes available.
Turning off LBC SDRAM support revealed a couple implict dependencies
in the tlb/law code that always expected an LBC SDRAM address.
This has been tested with the default 256MB module, a 512MB
a 1GB and a 2GB, of varying speeds, and the SPD autoconfiguration
worked fine in all cases.
The default configuration remains to go with the hard coded
DDR config, so the default build will continue to work on boards
where people don't bother to read the docs. But the advantage
of going to the SPD config is that even the small default module
gets configured for CL3 instead of CL4.
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 | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/doc/README.sbc8548 b/doc/README.sbc8548 index e6b8abe2b36..f9e2dea573c 100644 --- a/doc/README.sbc8548 +++ b/doc/README.sbc8548 @@ -62,6 +62,27 @@ a 33MHz PCI configuration is currently untested.) 02.00.00 0x1148 0x9e00 Network controller 0x00 => +Memory Size and using SPD: +========================== + +The default configuration uses hard coded memory configuration settings +for 256MB of DDR2 @400MHz. It does not by default use the DDR2 SPD +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. + +If you want to upgrade to larger RAM size, you can simply enable + #define CONFIG_SPD_EEPROM + #define CONFIG_DDR_SPD +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 +from the board's socket to resolve the above i2c address overlap +issue and allow SPD autodetection of RAM to work. + Updating U-boot with U-boot: ============================ |