[U-Boot] BSS footprint of FAT very high - SPL issues

[Aneesh V]

Dear Wolfgang,

On Tuesday 01 February 2011 01:25 PM, Wolfgang Denk wrote:
> Dear Aneesh V,
>
> In message<4D4798E2.3050500 at ti.com>  you wrote:
>>
>> I had been working on creating an MMC SPL for OMAP4. OMAP boards
>> typically support booting from the FAT partition of a removable SD/MMC
>> card. So, we need to have FAT support in the SPL. But I am having some
>> difficulties in adding FAT support to SPL.
>>
>> BSS footprint of fat.c is very high. It has three buffers each of size
>> 64KB. To workaround this problem I have done something like below(The
>> way x-loader works around this problem today).
>> CONFIG_SYS_SPL_FAT_BUFFER_BASE is in SDRAM.Is this ok?
>
> Why would that be necessary?  Just put the BSS segment in SDRAM, and
> everything is fine, isn't it?

SDRAM is initialized by the SPL. So, bss can not be initialized and
used until SDRAM initialization is complete. I would prefer to have
rest of the bss in internal RAM so that it's available as soon as we
enter C code.

>
>> Also, I was wondering why we need 3 such scratch buffers in this
>> implementation. I do not understand this code. But I was wondering if we
>> could work with just one 64K buffer?
>
> I have no idea.   I am not familiar with that code either.

Probably I will give it a try once I solve some other issues I am
facing in getting FAT to work.

Best regards,
Aneesh