[U-Boot] RFC: porting u-boot to sequoia based nand booting board

[Alex Waterman <awaterman@dawning.com>]

Stefan,

On 05/17/2011 09:41 AM, Stefan Roese wrote:
> What changes did you have to make? Some 8/16 bit related changes? Or something 
> else?

I changed the hard coded value of EBC0_CFG; I forced the chip->options field to have the 16 bit bus width flag set; in board_nand_select_device() I modified the value written to the NDFC_CCR register; I think that's primarily it. The hard coded registers could be made into CONFIG_SYS defines I think, but the bus width setting... Could we make a CONFIG_SYS define that specifies the width of the bus since during the spl we don't have access to the nand chip table?

> It should be the goal, to use *only* the common NDFC code. If you have found 
> some bugs, or you need some changes for 16bit devices, we should try to 
> integrate them into the common code.
I have seen issues with the nand_read_byte16() function in nand_base.c; it seems like the cpu_to_le16() should be the other way around: le16_to_cpu(). Other than that no bugs as far as I am aware.

> One idea behind the static declarations is to not pollute the namespace.
Ahh, understood.

>> Likewise much of our board specific support files are copies from the
>> sequoia code. Would it be better to symlink to the ones that are not
>> modified? Or is it OK to just copy the relevant source files into our own
>> board directory and make minor adjustments as needed?

> Usually we copy those files into a new board directly. When the similarities 
> are too big, then we should probably think about splitting to common parts 
> into some other directory (arch/powerpc/cpu/ppc4xx/ppc440epx.c ???).
OK, I see. Most of the code in board/amcc/sequoia is the same except for some of the sdram initialization and the sequoia.c file (which I renamed to tiger.c). Also the linker script differs slightly. How would we go about making those board files common (init.S, chip_config.c)?

Regards,
Alex

-- 
Alex Waterman
Computer Engineer
Phone: 215-896-4920
Email: awaterman at dawning.com