[U-Boot] [PATCH v3 0/9] Add a pre-relocation malloc() implementation

[Simon Glass]

Hi Tom,


On 23 July 2014 14:41, Tom Rini <trini at ti.com> wrote:
> On Wed, Jul 23, 2014 at 06:24:08AM -0600, Simon Glass wrote:
>> Hi,
>>
>> On 14 July 2014 18:16, Simon Glass <sjg at chromium.org> wrote:
>> > Hi Tom,
>> >
>> > On 14 July 2014 16:28, Tom Rini <trini at ti.com> wrote:
>> >>
>> >> On Thu, Jul 10, 2014 at 10:23:24PM -0600, Simon Glass wrote:
>> >>
>> >> > There has been talk on and off of a pre-relocation malloc() implementation.
>> >> > Driver model needs this so that it can work before relocation.
>> >> >
>> >> > A previous implementation was sent in a v1 series.
>> >> >
>> >> > This implementation works by allocating space on the stack. The benefit is
>> >> > that boards do not need to specify the address of the malloc() area, only
>> >> > the size. The down-side is that due to the way board_init_f() is called,
>> >> > architecture-specific code needs to be used to allocate the space.
>> >> >
>> >> > No clever algorithms are used to allocate space, free() is a nop and
>> >> > realloc() is not supported. This fits well with the desire to avoid wasting
>> >> > space on bucket tables and the hassle of supporting BSS data before
>> >> > relocation. We don't expect 'churn' in the pre-relocation case - we just
>> >> > want to allocate small amounts of memory temporarily.
>> >> >
>> >> > After relocation a new malloc() pool is created and the old one is lost,
>> >> > although pointers into it will survive the immediate process of relocation.
>> >> >
>> >> > Implementations are provided for sandbox and arm (32-bit only).
>> >> >
>> >> > A related change is made to the early init for each arch to make this work.
>> >>
>> >> My concern without a fix right now is how to make use of this in SPL,
>> >> when we're able to move SPL over to using still more generic code rather
>> >> than re-inventing the board_init_{f,r} wheels, in the case where we init
>> >> DRAM.
>> >
>> > One option would be to split this new code out into a separate file,
>> > and have two malloc() implementations:
>> >
>> > - big one - falls back to small one pre-relocation
>> > - small one - used for SPL
>>
>> I'm thinking of applying this to the dm repo now, except for the arm
>> patches where I would like to get Albert's ack (so I'll wait a few
>> more days).
>>
>> Any objections?
>
> I think we'll be OK.  I checked over the callpath again on OMAP parts
> and we setup DDR prior to _main (in SPL) so we'll be fine.

OK, I'll prepare a pull request for the ARM-related malloc() patches
soon, along with the GPIO things (sandbox only at this stage as we
need to make progress on applying exynos patches first).

Regards,
Simon