linux-kernel - Re: [PATCH 1/5] arm64: dts: allwinner: a64: Add i2c0 pins

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Message-ID: <20180313152744.fb2oo44v6lr4gyha@flea>
Date:   Tue, 13 Mar 2018 16:27:44 +0100
From:   Maxime Ripard <maxime.ripard@...tlin.com>
To:     Harald Geyer <harald@...ib.org>
Cc:     André Przywara <andre.przywara@....com>,
        Chen-Yu Tsai <wens@...e.org>, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, Icenowy Zheng <icenowy@...c.io>,
        info@...mex.com
Subject: Re: [PATCH 1/5] arm64: dts: allwinner: a64: Add i2c0 pins

On Tue, Mar 13, 2018 at 09:46:51AM +0100, Harald Geyer wrote:
> André Przywara writes:
> > On 12/03/18 16:10, Harald Geyer wrote:
> > > Add the proper pin group node to reference in board files.
> > > 
> > > Signed-off-by: Harald Geyer <harald@...ib.org>
> > 
> > That looks correct to me, so:
> > 
> > Reviewed-by: Andre Przywara <andre.przywara@....com>
> > 
> > But out of curiosity, what is this used for? In patch 5/5 I see it being
> > used, but without a clue for what? Shouldn't enabling an I2C node be
> > accompanied by some child node, presenting the device on the bus?
> > I guess this I2C is not on some kind of "header" on that laptop?
> 
> I enabled it because the ANX6345 eDP-bridge is on that bus. There is
> no linux (mainline) driver for this chip at the moment, the bootloader
> initializes it. However I'm using the i2c-dev driver to read (and maybe)
> change some register values from user space.
> 
> i2cdetect sees devices at 0x38, 0x39 and 0x3d - all of which might
> be the ANX6345. I haven't looked into this in detail.

That's alright then, just put a comment in the DT on what this bus is
used for.

Thanks!
Maxime

-- 
Maxime Ripard, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com

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