linux-kernel - Re: [PATCH v4] i2c: aspeed: Deassert reset in probe

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Date:   Mon, 6 Nov 2017 08:19:58 -0600
From:   Rob Herring <robh+dt@...nel.org>
To:     Wolfram Sang <wsa@...-dreams.de>
Cc:     Joel Stanley <joel@....id.au>,
        Brendan Higgins <brendanhiggins@...gle.com>,
        Philipp Zabel <philipp.zabel@...il.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Andrew Jeffery <andrew@...id.au>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] i2c: aspeed: Deassert reset in probe

On Sun, Nov 5, 2017 at 6:49 AM, Wolfram Sang <wsa@...-dreams.de> wrote:
> On Wed, Nov 01, 2017 at 10:53:30AM +1030, Joel Stanley wrote:
>> In order to use i2c from a cold boot, the i2c peripheral must be taken
>> out of reset. We request a shared reset controller each time a bus
>> driver is loaded, as the reset is shared between the 14 i2c buses.
>>
>> On remove the reset is asserted, which only touches the hardware once
>> the last i2c bus is removed.
>>
>> The reset is required as the I2C buses will not work without releasing
>> the reset. Previously the driver only worked with out of tree hacks
>> that released this reset before the driver was loaded. Update the
>> device tree bindings to reflect this.
>>
>> Signed-off-by: Joel Stanley <joel@....id.au>
>> ---
>> v4:
>>   - Make reset required and update device tree bindings
>
> For that change, I'd like to have an ack from Rob first. Won't that
> cause problems when you update only the kernel and keep the "old"
> devicetree?

Given it didn't really work as explained above, I'm okay with the change.

Acked-by: Rob Herring <robh@...nel.org>