linux-kernel - Re: [PATCH 4/4] ARM: multi_v7_defconfig: Switch AXP20x driver from module to built-in

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Message-ID: <20170522074414.3qz2wpw4cs2btkhv@flea.lan>
Date:   Mon, 22 May 2017 09:44:14 +0200
From:   Maxime Ripard <maxime.ripard@...e-electrons.com>
To:     Kevin Hilman <khilman@...libre.com>
Cc:     Rask Ingemann Lambertsen <rask@...melder.dk>,
        Chen-Yu Tsai <wens@...e.org>,
        Russell King <linux@...linux.org.uk>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/4] ARM: multi_v7_defconfig: Switch AXP20x driver from
 module to built-in

Hi Kevin,

On Thu, May 18, 2017 at 11:59:50AM -0700, Kevin Hilman wrote:
> On Fri, Mar 17, 2017 at 10:39 AM, Kevin Hilman <khilman@...libre.com> wrote:
> > On Fri, Feb 10, 2017 at 12:42 AM, Maxime Ripard
> > <maxime.ripard@...e-electrons.com> wrote:
> >> On Wed, Feb 08, 2017 at 11:09:31PM +0100, Rask Ingemann Lambertsen wrote:
> >>> The AXP20X regulator support is currently built as a module, which means
> >>> it's not available until the root fs has been mounted, but the boot loader
> >>> might not have enabled the required regulators, so build their drivers
> >>> into the kernel.
> >>>
> >>> Signed-off-by: Rask Ingemann Lambertsen <rask@...melder.dk>
> >>
> >> Queued for 4.12.
> >
> > Hello, kernelci.org is reporting boot failures on sun5i-r8-chip in
> > linux-next[1]  for a few days and with a variety of defconfigs. I
> > bisected it[2] down to this patch.
> >
> > I verified that reverting this patch on top of next-20170310 makes my
> > chip board boot again.
> 
> FYI... this board is still broken in linux-next (and now in mainline),
> and reverting $SUBJECT patch still makes it work.
> 
> Is nobody else using mainline on this board?

I thought about that during the weekend, and it might just be a
symptom.

The CHIP has brown out issues, especially when you enable the WiFi
chip, which should happen around the time of the failure when the PMIC
regulator support is compiled as a module.

We mitigate that in upstream's U-Boot by enabling the two regulators
for the WiFi chip in U-boot, which levels a bit the current over the
boot.

You have a few ways to prevent that from happening. Having a better
power supply / cable will help, I'm not sure how reasonable that is.

Another thing that can work is, if your USB plugs can take it, to
increase the overcurrent trigger in the PMIC, ideally in U-Boot.

The last, and probably cleaner one, would be to just power it through
the 5v input on its header, and not the USB. There's not current
limitation there, so it shouldn't cause any problems anymore.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

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