From mboxrd@z Thu Jan 1 00:00:00 1970 From: Larry Johnson Date: Thu, 20 Mar 2008 11:06:27 -0500 Subject: [U-Boot-Users] [PATCH] ppc4xx: Don't use last 256 bytes of SDRAM, workaround for 440EPx CHIP 11 errata In-Reply-To: <200803201129.06602.sr@denx.de> References: <20080320100330.B00C624A87@gemini.denx.de> <200803201129.06602.sr@denx.de> Message-ID: <47E28B83.2080802@acm.org> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de 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. > > Thanks. > > Best regards, > Stefan Hi Stefan, Having multiple implementations of the 440EXp SDRAM setup code is, in itself, less than ideal. One alternative is to have a 440EPX board with on-board SDRAM chips fake an array of SPD bytes describing the chips, and pass it to the "denali_spd_ddr2.c" code. The SPD code then becomes the single location for the technology of how to configure the Denali SDRAM controller. The additional benefit (for me, anyway :-) ) is having more eyeballs on the SPD code, with more opportunities for testing, bug fixing, and enhancements. Best regards, Larry