[U-Boot-Users] [PATCH] ppc4xx: Don't use last 256 bytes of SDRAM, workaround for 440EPx CHIP 11 errata

[Dave Littell]

Stefan Roese wrote:
> Hi Wolfgang,
> 
> On Thursday 20 March 2008, Wolfgang Denk wrote:
>>> This patch adds this workaround for the following 440EPx boards:
>>> sequoia, lwmon5. Others should probably follow this example.
>> OK, the default configs for Sequoia doesn't use shared log buffer, and
>> the lwmon5 uses CONFIG_ALT_LB_ADDR (i. e. it puts the log buffer in
>> OCM), so these boards will work.
>>
>> But any changes to the configuration may easily break this again.
> 
> Understood.
> 
>> I don't like the idea that  each  affected  board  has  to  fix  this
>> (probably  differently)  in  it's board config file. I would prefer a
>> fix (common to all affected boards) in one central location.
> 
> I don't like this either. But I have not come up with a "generic" solution 
> till now. It's not so easy since the 440EPx SDRAM setup code is sometimes 
> common (cpu/ppc4xx/denali_spd_ddr2.c) and sometimes board specific. And it 
> gets even more complicated when ECC initialization is needed too. So 
> currently I have no "better" solution as to do it in a board specific way.
> 
> As always, patches implementing a "better" more generic solution are welcome.
> 

Hi all,

This may not be the "better, more generic solution", but I just added a
CONFIG_CHIP_11_ERRATA option and code in lib_ppc/board.c to trim off
only 256 bytes before the optional log buffer is carved out.

There's a kernel patch for this errata that trims the memory length.  If
that patch is applied, does the kernel still need to be made to
understand the changed logbuffer location?


Thanks,
Dave