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

[André Przywara]

On 29/12/2018 22:10, Olliver Schinagl wrote:

Hi Olliver,

> Luckily we have had no problem with this on our boards, but its sad to
> see this patch reverted due to the buggy ddr implementation ...

This whole SPL is quite a sensitive construct, so moving things around
can have interesting effects. For instance try to use any .bss variables
(global variables initialised to 0) before the DRAM init.
Also especially the DRAM controller driver was written basically without
any single line of documentation. So bear with us if we didn't get
everything 100% correct.

I actually wanted to ask you: what was your patch meaning to fix in the
first place? All the patch did was to move the DRAM init after the CPU
clock setting, which was the exact reason for the breakage.
What that power_failed check does is to avoid increasing the CPU
frequency, before and after that patch. There are no other consequences.
So the effect would be just a mere change in the order of reporting,
since we continue execution in any case.

So was that the only purpose of the patch? I believe that could be
better done this way, without any side effects:
....
#endif
#endif

	if (power_failed)
		printf("Error setting up the power controller.\n"
		       "CPU frequency not set.\n");
 <... DRAM init ...>
	
	if (!power_failed)
		clock_set_pll1(CONFIG_SYS_CLK_FREQ);

....

> 
> Curiosity is getting the better of me and I cant seem to be able to
> reproduce the problem. So could you be a little bit more specific on the
> bug please?

As I wrote in the commit message, the OrangePi Zero breaks straight away
with this patch, all of the time: 0 MB DRAM. I don't have any other
affected board to test on, but there were reports of more boards not
working as well.

Since we shouldn't allow such drastic regressions, I believe it's best
to just revert the patch, given the short time to the release. Since I
consider the original patch more cosmetic than anything else, I believe
this is justified.

Cheers,
Andre

> On December 29, 2018 7:53:49 PM GMT+01:00, Jagan Teki
> <jagan at amarulasolutions.com> wrote:
> 
>     On Wed, Dec 19, 2018 at 6:32 PM Andre Przywara <andre.przywara at arm.com> wrote:
> 
> 
>         From: "From: Karl Palsson" <karlp at tweak.net.au>
> 
>         Commit a8011eb84dfa("sunxi: board: Print error after power
>         initialization
>         fails") moved the DRAM init after the increase of the CPU clock
>         frequency. This lead to various DRAM initialisation failures on some
>         boards (hangs or wrong size reported, on a NanoPi Duo2 and OrangePi
>         Zero, for instance). Lowering the CPU frequency significantly
>         (for instance
>         to 408 MHz) seems to work around the problem, so this points to
>         some timing
>         issues in the DRAM code.
> 
>         Debugging this sounds like a larger job, so let's just revert
>         this patch
>         to bring back those boards.
>         Beside this probably unintended change the patch just moved the
>         error
>         message around, so reverting this is not a real loss.
> 
> 
>     Better mark this as TODO somewhere, may be some one look it later.
> 
> 
>         This reverts commit a8011eb84dfac5187cebf00ed8bc981bdb5c1fa1.
> 
>         Tested-By: Priit Laes <plaes at plaes.org>
>         Signed-off-by: Karl Palsson <karlp at tweak.net.au>
>         Signed-off-by: Andre Przywara <andre.przywara at arm.com>
> 
> 
>     Applied to u-boot-sunxi/master
> 
> 
> -- 
> Sent from my Android device with K-9 Mail. Please excuse my brevity.