From: Bruce Boettjer [mailto:bruceb@momenco.com] Sent: Friday, December 12, 2003 6:51 PM To: 'Bill Hargen'; u-boot-users@lists.sourceforge.net Subject: RE: u-boot patches for BUBINGA
Just a quick note... The memory config on the 405EP Eval board is still incorrect. The Physical DIMM is 64-bit, but the memory bus is 32-bit... therefore, only half of the memory gets used...
In spd_sdram.c, I added a line after 354 that divided 'total_size' by two. This appears to do the init correctly.
My understanding of the Bubinga design is that the 64-bit wide memory DIMM gets used as two banks of 32-bits each. There is some discussion of this in the manual for the eval board. My board has a DIMM marked as 128MB and u-boot is reporting the same and using it as two 64MB banks. However, the manual is carefull to not promise exactly what memory DIMM is shipped with the board, so your system could be different. But still, the basic design is to use a 64-bit DIMM as two 32-bit banks. I'm assuming that the SDRAM SPD code is doing the proper math to make the sizing work. I didn't have to do a divide-by-two. My only problem was that the code was using banks 0 and 2 instead of 0 and 1. (Worked fine right up to the point where u-boot jumps to its RAM copy at the top of the second bank!)
BTW-Is anyone able to get a uImage built kernel to boot off a 405EP Eval board? I'd love to know what version... My kernel dies pretty early...
I'm using the MontaVista 3.0 package. They released a new LSP for the Bubinga during the summer. It didn't work because it was assuming that the board information structure passed from the boot loader was the format used by IBM's boot code. u-boot is different - similar stuff like memory size, but at different structure offsets. I had to change it to expect the u-boot structure. Everything mapped OK except for the "PLLOUTA" clock speed that used used to compute serial port baud rate clocks. I recomputed it based on another clock speed and some clock divisor register settings.
The only strange thing was that I didn't see any code in the MontaVista package to deal with the PPCBoot/u-boot structure. I would have expected some of the PPC Linux ports to use this structure. Perhaps MontaVista has stripped out such stuff from the LSP. This also may be addressed in Wolfgang's u-boot manual, and probably wouldn't have been an issue if I was using his ELDK.
--Bill