[U-Boot] disabling mmc in spl when booting using bootrom

[Simon Glass]

Hi Sandy,

On 12 August 2016 at 11:35, Sandy Patterson <apatterson at sightlogix.com> wrote:
>
>
> On Fri, Aug 12, 2016 at 1:20 PM, Simon Glass <sjg at chromium.org> wrote:
>>
>> Hi Ziyuan,
>>
>> On 11 August 2016 at 05:35, Ziyuan Xu <xzy.xu at rock-chips.com> wrote:
>> >
>> >
>> > On 2016年08月11日 19:31, Sandy Patterson wrote:
>> >>
>> >> Simon,
>> >>
>> >> I am trying to format a patch to disable MMC in the SPL if booting main
>> >> u-boot using BOOTROM, therefore the SPL MMC isn't needed.
>> >>
>> >> Is the best solution to wrap every header file (rock2.h
>> >> firefly-rk3288.h,
>> >> etc) with ifdefs on the BACK_TO_BROM define? Or would it be better to
>> >> move
>> >> the SPL MMC define into rk3288-common.h and just have chromebook_jerry
>> >> undef
>> >> it like it does the SPL GPIO code.
>> >>
>> >> With that change, enabling BOOT_TO_BROM shrinks the spl from 32K to
>> >> 23K.
>> >
>> > Note that, firefly-rk3288 use OF_PLATDATA, we will use
>> > u-boot-spl-no-dtb.bin
>> > instead of u-boot-spl-dtb.bin, and the size of u-boot-spl-no-dtb.bin is
>> > almost 23K.
>> >
>> > @Simon, I think we will update doc/README.rockchip if you insist on
>> > OF_PLATDATA for firefly-rk3288. we no longer use u-boot-spl-dtb.bin.:-)
>>
>> I don't insist :-)
>>
>> I really don't like OF_PLATDATA. But it cuts the size down a lot
>> (~6KB) and we are otherwise always running out of space on rk3288.
>>
>> If there is a better idea, let's have it. Otherwise, yes we can update the
>> docs.
>
>
> @Ziyuan, I did my testing on rock2 which doesn't use OF_PLATDATA, the
> firefly
> board should see the same final size which is roughly equivalent to the
> current
> firefly SPL size.
>
> We ran out of space in SPL. I too was afraid of using OF_PLATDATA mostly
> from
> Simon's commit message.
>
> I would propose moving to using the BOOTROM to load U-Boot proper. You
> shouldn't
> need any of the media drivers since the BOOTROM was already able to load the
> SPL
> it should be fine loading the full U-Boot.
>
> I get 9K from removing MMC from rock2. I'm happy to write a patch that
> applies this logic
> to the remainder of the rk3288 boards if that's the way you'd like to go.
> You could test it by
> enabling the BOOT_TO_BROM config.

My concern with the Rockchip back-to-brom feature is that then U-Boot
cannot load U-Boot normally as SPL likes to do. I think it is fine
when we are short on space, but OF_PLATDATA fixes that.

So I think the back-to-rom feature need to be optional on boards which
don't have to use it, since it uses a non-standard boot approach,

Regards,
Simon