linux-kernel - Re: [PATCH] ARM: dts: Add ddc i2c reference to veyron

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Date:	Thu, 3 Sep 2015 09:28:09 -0700
From:	Doug Anderson <dianders@...omium.org>
To:	Lucas Stach <l.stach@...gutronix.de>
Cc:	Rob Herring <robherring2@...il.com>,
	Mark Rutland <mark.rutland@....com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Heiko Stuebner <heiko@...ech.de>,
	Pawel Moll <pawel.moll@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Brian Norris <briannorris@...omium.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
	Rob Herring <robh+dt@...nel.org>,
	Yakir Yang <ykk@...k-chips.com>,
	Kumar Gala <galak@...eaurora.org>,
	姚智情 <mark.yao@...k-chips.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Alexandru Stan <amstan@...omium.org>
Subject: Re: [PATCH] ARM: dts: Add ddc i2c reference to veyron

Lucas,

On Thu, Sep 3, 2015 at 9:13 AM, Lucas Stach <l.stach@...gutronix.de> wrote:
>> 6. Once you start using the dw_hdmi's i2c block with the currently
>> posted patch against mainline (to do this you not only need the patch
>> but you need to remove the ddc-i2c-bus property, set the pinmux, and
>> disable i2c5) then you'll see a bonafide i2c bus exposed to Linux.  In
>> my case this stole i2c0 away from the builtin SoC I2C bus and caused
>> the SoC I2C bus to fail to probe.  Doh.
>>
> This shouldn't happen. I don't know if the patches landed yet, but I
> know Wolfram (i2c maintainer) had patches to reserve the range of bus
> numbers that are fixed by alias nodes and don't hand out those numbers
> to adapters with a dynamic bus number allocation.
>
>> 7. I was trying to solve #6 by adding an "of_node" to the i2c bus
>> which allowed me to give it a (non-conflicting) bus ID.
>>
> This should not be needed.

Ah.  It's very possible that the issue is due to the fact that I was
testing this on an old kernel (3.14) that's missing that feature.  OK,
if that's fixed then at least the actual bug (making i2c0 fail to
load) is not a problem.  It'd still be nice to be able to assign a bus
number to this bus just to make reading of the logs easier, but it's
not a functionality requirement.

-Doug
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