[U-Boot] Reboot and audio on Orange Pi mini (was: [linux-sunxi] Re: [PATCH v3 0/9] Stop AXP from crashing when enabling LDO3)

[Stefan Monnier <monnier@IRO.UMontreal.CA>]

> Well, f you have the hardware, then there's only one way to find out:
>
> 1) Apply patchset
> 2) Add following into boards defconfig:
> CONFIG_AXP_ALDO3_INRUSH_QUIRK=y
> 3) If it still fails to reboot, add following
> CONFIG_AXP_ALDO3_VOLT_SLOPE_08=y

Hmm... I tried it and it worked: it now reboots flawlessly.
I tried it first with both setting, then only with the first...
... then without any
... then back with my old U-Boot
and now I can't reproduce the hang that normally happens at almost every
reboot.  Not sure if I should rejoice or what.

One thing I noticed along the way: on my Orange Pi mini, there's
a regression in U-Boot that happened between 2015.07 and 2015.10.
All version I tried starting with 2015.10 cause a constant "humming" on
the audio output (the plain old TRRS plug audio output).

During a reboot, the humming briefly disappears after Linux causes the
reboot and before U-Boot has fully started, but it quickly comes
pretty loudly.  As soon as U-Boot passes the control to the Linux kernel
the humming gets a bit less loud, but remains there.
Playing a song doesn't seem to affect the humming.

Interestingly, if I boot a Linux kernel with HDMI support, then at some
point during the Linux boot, the humming disappears.  But sadly, I need
to use a DTB with the HDMI output disabled because of some unexplained
interaction with the normal audio codec (see the «Odd "jump" when
playing music on A20» thread in the linux-sunxi mainling list, spanning
July to October).


        Stefan "back at U-Boot 2015.07"