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

[Tom Rini <trini@konsulko.com>]

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@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).

> This sounds like there could be some boards using nand that rely on
> malloc (that's where I got the inspiration from for this) and others
> using mmc that rely on a decent size stack. I wonder if there is a
> #define that we can base off of to provide the best of both? Its not
> that great having two env drivers that have opposite requirements but
> I certainly don't want to change one to make them consistent it it
> will break boards.

My first guess is that NAND should also be converted to DDR not stack (I
too found the NAND example, switched MMC to it, and then Wolfgang/others
pointed out that really stack is where this kind of allocation should
be, iirc, but then didn't get a chance to dig back at NAND).

-- 
Tom
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