[U-Boot] [linux-sunxi] [PATCH] Revert "sunxi: board: Print error after power initialization fails"

[André Przywara]

On 19/12/2018 00:51, André Przywara wrote:
> On 18/12/2018 12:06, Jagan Teki wrote:
>> On Tue, Dec 18, 2018 at 4:09 PM <karlp at tweak.net.au> wrote:
>>>
>>> From: Karl Palsson <karlp at tweak.net.au>
>>>
>>> This reverts commit a8011eb84dfac5187cebf00ed8bc981bdb5c1fa1
>>>
>>> This causes DRAM init failures on (at least)
>>> * allwinner h3 nanopi-duo2
>>> * allwinner h2+ orangepi zero v1.1
>>>
>>> Signed-off-by: Karl Palsson <karlp at tweak.net.au>
>>> ---
>>>
>>> Ideally, this should get into 2019.01, so that this release is not
>>> broken on those targets.
>>
>> Better to understand the issue here, since I have BPI-M2+ which boots
>> fine w/o this revert.
> 
> Could this be a .bss issue? This lies in DRAM and is thus only available
> *after* DRAM init. IIRC we silently rely on not accessing anything in
> .bss before the DRAM is up, see 59d07ee08e85 for instance.
> I don't immediately spot any .bss usage in clock_set_pll1(), though.
> 
> Or is the 1GHz CPU clock speed too fast for the DRAM init? If I am not
> mistaken, we run with 24MHz before, so there might be some "natural"
> delay in some setup routines. Some DRAM chips or board layout might be
> more susceptible to this than others, which might explain why it only
> fails on some boards.

Just did some testing on my OrangePi Zero: if I force the CPU frequency
to 408 MHz, it works, but fails with the standard 1008 MHz.
So this smells that we indeed miss some delays in the DRAM setup code,
which sounds tedious to find. There are a number of delays, but those
are fine as they are timer controlled, so independent from the CPU
frequency.

For now I think that reverting would be the easiest solution. Somewhat
in contrast to what the commit message says, we don't really change
anything in terms of error *checking*, as the code carries on anyways
(just without increasing the CPU frequency). The only real difference is
the order of CPU clock setup and DRAM init.

Karl, can you please amend the commit message to mention the CPU
frequency issue?

> So if the original patch is about bailing out on error early, can't we
> just do *that* before the DRAM init, keeping the CPU clock setup still
> after DRAM?

Just checked, this works as well, but is a bit pointless. Just reverting
this and meanwhile checking the DRAM init code seems the easier solution.

Cheers,
Andre