[U-Boot] [PATCH 1/2] bouncebuf: Add static buffer allocation method for SPL.

[Simon Goldschmidt]

On Tue, May 7, 2019 at 4:11 PM Christoph Müllner
<christoph.muellner at theobroma-systems.com> wrote:
>
>
>
> On 07.05.19 15:55, Marek Vasut wrote:
> > On 5/7/19 3:55 PM, Christoph Müllner wrote:
> >>
> >>
> >> On 07.05.19 15:52, Marek Vasut wrote:
> >>> On 5/7/19 3:45 PM, Christoph Müllner wrote:
> >>>>
> >>>>
> >>>> On 07.05.19 15:06, Marek Vasut wrote:
> >>>>> On 5/7/19 11:09 AM, Christoph Muellner wrote:
> >>>>>> If we are using malloc-simple, we get into the problem, that
> >>>>>> calls to free() won't free any memory. When using bouncebuf
> >>>>>> in SPL with malloc-simple this means, that every allocated buffer
> >>>>>> is lost. This can quickly consume the whole heap.
> >>>>>
> >>>>> When does such a scenario happen ?
> >>>>
> >>>> RK3399 with mainline U-Boot and mainline ATF.
> >>>> We have 0x4000 bytes heap in SPL.
> >>>> For the SRAM part of ATF we need to allocate 0x2000-0x2200 bytes.
> >>>> For the PMUSRAM part about the same again.
> >>>>
> >>>> I tried to increase the heap size to 0x10000, but that seems
> >>>> to break some unchecked assumptions about the memory layout,
> >>>> because then SPL resets very early.
> >>>
> >>> So what calls this malloc-free pair so often to spend all the simple
> >>> malloc area ?
> >>
> >> The bouncebuf code (bounce_buffer_start(), which does memalign().
> >> It is called twice (once for SRAM and once for PMUSRAM) as mentioned above.
> >>
> >> That's all part of loading the ATF parts (on RK3399 we have normal ATF code,
> >> SRAM code and PMUSRAM code).
> >
> > Can you switch to full malloc ?
>
> Tested that as well, but that did not work either (again SPL crashes quite early).
>
> I think the reason is the following:
> Full malloc needs the data section to be working for the global variables
> (besides gd fields). I think that's not possible in very early SPL stages,
> where the first pages are going to be mapped (and malloc is used for allocating
> the page table entries).

Exactly. I think you're at least the third person on this list stumbling
accross this in the last weeks :(

Regards,
Simon