[U-Boot] [PATCH] env_mmc: avoid stack allocation for env

[Simon Glass]

Hi,

On 13 May 2015 at 16:40, Tim Harvey <tharvey at gateworks.com> wrote:
> On Wed, May 13, 2015 at 12:58 PM, Tim Harvey <tharvey at gateworks.com> wrote:
>> On Tue, May 12, 2015 at 8:14 AM, Tom Rini <trini at konsulko.com> wrote:
>>> On Mon, May 11, 2015 at 12:08:25PM -0700, Tim Harvey wrote:
>>>> On Fri, May 8, 2015 at 4:14 PM, Tom Rini <trini at konsulko.com> wrote:
>>>> > On Sat, May 09, 2015 at 12:15:37AM +0200, Marek Vasut wrote:
>>>> >> On Friday, May 08, 2015 at 11:51:36 PM, Tim Harvey wrote:
>>>> >> > Allocating space for temporary env on the stack makes env_relocate_spec()
>>>> >> > unsuitable for SPL environments which have very little stack.
>>>> >>
>>>> >> Well yeah, but what if you don't have malloc area ? I'd expect that
>>>> >> the be the case in SPL quite often.
>>>> >
>>>> > OK, hold up.  We went through this a while back which is why things are
>>>> > how they are today.  First, we have things setup today such that you can
>>>> > throw stack (at the point we do env in SPL) into DDR.  This means we can
>>>> > keep doing things the way they are.  You can take a look at
>>>> > include/configs/am335x_evm.h and where CONFIG_EMMC_BOOT is set, that's
>>>> > how we do what it looks like you're trying to do on imx6 but on TI
>>>> > am335x.
>>>>
>>>> Yes, I'm doing this on Gateworks Ventana (board/gateworks/gw_ventana)
>>>> based on IMX6 which has a limmited stack size during SPL. I don't see
>>>> anything magic in include/configs/am335x_evm.h that catches my
>>>> attention. Do you know where the code is that lets you point the stack
>>>> to DDR? It sounds like that's what I need.
>>>
>>> Ah oops.  Kconfig, we use Kconfig now :)
>>> configs/am335x_evm_defconfig:CONFIG_SPL_STACK_R=y
>>> configs/am335x_evm_defconfig:CONFIG_SPL_STACK_R_ADDR=0x82000000
>>>
>>> That's moving stack to DDR and then grabbing 0x82000000 for stack (base
>>> + 0x02000000 which is not too high, not too low, not likely to stomp on
>>> the kernel).
>>
>> thats strange... common/spl/spl.c uses CONFIG_SPL_STACK_R as the
>> address not CONFIG_SPL_STACK_R_ADDR - how can that even compile?
>>
>> http://git.denx.de/?p=u-boot.git;a=blob;f=common/spl/spl.c;#l324
>
> Tom,
>
> I don't really understand the CONFIG_SPL_STACK_R usage at all. The
> only thing that uses CONFIG_SPL_STACK_R is spl_relocate_stack_gd which
> is called from arch/arm/lib/crt0.S 'after' board_init_f() is called,
> which will never return for SPL because we loaded and jumped to
> u-boot.img.
>
> How is this working for the am335x stuff?

Tom just forwarded me this thread. There is definitely something
missing upstream compared to my local branch. I'll take a look and see
what I missed.

Regards,
Simon