[U-Boot] Pine64 problems with GPT partitions

[Andre Przywara]

Hi Guillaume,

On 26/06/18 15:18, guillaume.gardet at free.fr wrote:
> 
> Hi Andre,
> 
> You are the maintainer of Pine64 in U-Boot, so I want to let you know that Pine64 has problems to access GPT partitions, whereas MBR partitions seem to be OK.

Is that with the latest U-Boot?

In general GPT is problematic on any Allwinner board, since a standard
GPT (sectors 1-33) collides with the SPL location on the media (sectors
16-80). The latter is mandated by the BootROM and cannot be changed
(apart from wild hacks to make them coexist).
One workaround (apart from using MBR) is to restrict the number of GPT
partitions to 56, so that the GPT ends at sector 16. However this
is a bit fragile, since GPT mandates the first 34 sectors to be
available, so any valid partition tool could clobber the SPL at any time.
So can you check whether this is a problem here or did you take this
already into account?
Andreas and Alex should know about this.

> There is a bug report from openSUSE here with additional informations: https://bugzilla.opensuse.org/show_bug.cgi?id=1098550

But this reads more like a separate problem. I have heard reports in the
past that *some* MMC reads (from some sectors?) are very slow in U-Boot,
but that seemed to be a problem with the ext4 U-Boot driver, possibly in
conjunction with the Allwinner MMC driver. But I couldn't really
reproduce this yet reliably.

Another thing that triggered error reports in the past were unreliable
SD cards, which led to seemingly random errors, in some circumstances.
Has the SD card been changed to rule this out?
Also a Pine64 classic is an insufficient power supply, which happens to
work *most of the time*. Though I doubt that this is a problem here...

Cheers,
Andre.