[U-Boot] Pine64 problems with GPT partitions

[Alexander Graf]

On 06/26/2018 04:39 PM, Andre Przywara wrote:
> 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.

Yes, we decrease the size of the GPT in our image creation already.

>
>> 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?

Yes, we used multiple SD cards. This also seems to be a regression - a 
few months back Andreas' Pine64 worked just fine.

It's very easy to reproduce. Grab a random SD card with an FS on it and 
just do

   U-Boot # ls mmc 0:1

a few times. I wasn't able to run it more than 10 or 20 times without at 
least one invocation that errored 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...

I just used a random power plug I had lying around, but given that this 
is reported as a regression, I'm much more inclined to believe that it's 
a problem in the clock tree. Unfortunately I don't have anything at hand 
to properly analyze the SD clock coming in.


Alex