linux-kernel - Re: Re: [PATCH v2] ARM: dts: sun8i-r40: remove unused GPIO regulator

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Message-ID: <CAGb2v64ovacuS+G+k3zBvQR+rW2_TSYh4p5frj7fLxz81K9Kmg@mail.gmail.com>
Date: Mon, 23 Dec 2024 01:18:18 +0800
From: Chen-Yu Tsai <wens@...e.org>
To: Hermann Lauer <Hermann.Lauer@....uni-heidelberg.de>
Cc: Icenowy Zheng <uwu@...nowy.me>, Andre Przywara <andre.przywara@....com>, 
	Hermann.Lauer@...-heidelberg.de, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Jernej Skrabec <jernej.skrabec@...il.com>, Samuel Holland <samuel@...lland.org>, 
	devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-sunxi@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: Re: [PATCH v2] ARM: dts: sun8i-r40: remove unused GPIO regulator

On Sat, Dec 21, 2024 at 1:21 AM Hermann Lauer
<Hermann.Lauer@....uni-heidelberg.de> wrote:
>
> Hi,
>
> On Sat, Dec 14, 2024 at 03:13:23PM +0800, Icenowy Zheng wrote:
> > > CC:ing Icenowy, who added the regulator originally, with commit
> > > 0ca12c1ee43c ("ARM: sun8i: r40: add 5V regulator for Banana Pi M2
> > > Ultra").
> ...
> > > Icenowy: can you clarify what "newer" version this was referring to
> > > in
> > > that commit message? That commit in itself doesn't seem to do
> > > anything,
> > > as the regulator isn't referenced, and it's not always-on. It's only
> > > later when the USB nodes were added that it got used?
> > > So was PH23 really necessary? As Hermann reports, setting PH23 on a
> > > v1.1
> > > makes it reboot.
>
> diagnosed that futher now: PH23 is indeed powering the USB-Ports. Whats
> happens ist that I powered the board through the micro USB port which turned
> out to be limited to 900mA in axp221s. So the setting of reg 0x30 is
> the real culprit: Setting the two lowest bits in this register allows
> unlimited power over micro usb.
>
> In U-Boot:
>  i2c dev 0
>  i2c mw 34 30 63
>
> Or power the board through the barrel connector.
>
> In all cases the kernel turns on USB-A power and boots.
>
> > I am not sure, the schematics I have here (which says V1.0) have PH23
> > as NC... Well, the M2 Berry schematics have PH23 as 5V EN, maybe I
> > messed up M2U and M2B when developing?
>
> While V1.0 didn't need the PH23 setup due to nc, V1.1 needs it. Maybe V1.1
> was already on the horizon...

It seems this patch isn't needed then?


ChenYu

> Thanks for the insights and your support, guys.
>
> With seasons greetings
>   Hermann