linux-kernel - Re: [PATCH v3 1/5] i2c: mv64xxx: Add reset deassert call

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Date:	Fri, 7 Mar 2014 10:34:33 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Maxime Ripard <maxime.ripard@...e-electrons.com>
Cc:	Wolfram Sang <wsa@...-dreams.de>, linux-kernel@...r.kernel.org,
	zhuzhenhua@...winnertech.com, linux-sunxi@...glegroups.com,
	kevin.z.m.zh@...il.com, sunny@...winnertech.com,
	shuge@...winnertech.com, linux-arm-kernel@...ts.infradead.org,
	linux-i2c@...r.kernel.org
Subject: Re: [PATCH v3 1/5] i2c: mv64xxx: Add reset deassert call

On Fri, Mar 07, 2014 at 11:07:51AM +0100, Maxime Ripard wrote:
> Hi Russell,
> 
> On Fri, Mar 07, 2014 at 09:52:23AM +0000, Russell King - ARM Linux wrote:
> > On Tue, Mar 04, 2014 at 05:28:37PM +0100, Maxime Ripard wrote:
> > > The Allwinner A31 SoC using that IP has a reset controller maintaining
> > > it reset unless told otherwise.
> > > 
> > > Add some optional reset support to the driver.
> > > 
> > > Signed-off-by: Maxime Ripard <maxime.ripard@...e-electrons.com>
> > > Reviewed-by: Gregory CLEMENT <gregory.clement@...e-electrons.com>
> > > Tested-by: Gregory CLEMENT <gregory.clement@...e-electrons.com>
> > 
> > This appears to be causing some build errors in Olof's next builder
> > for many of the ARM platforms which make use of this:
> > 
> > drivers/i2c/busses/i2c-mv64xxx.c:924: undefined reference to `reset_control_assert'
> > drivers/i2c/busses/i2c-mv64xxx.c:904: undefined reference to `reset_control_assert'
> > drivers/i2c/busses/i2c-mv64xxx.c:771: undefined reference to `devm_reset_control_get'
> > drivers/i2c/busses/i2c-mv64xxx.c:778: undefined reference to `reset_control_deassert'
> 
> The reset framework doesn't define its functions when its not
> selected, and somehow I think it was not here. What's odd is that
> there is an explicit select on RESET_CONTROLLER in the Kconfig. Maybe
> it's the circular dependency issue that has been reported that cause
> this and Wolfram sent a patch for: http://patchwork.ozlabs.org/patch/327573/

If that patch has been taken, then yes, it will have caused the above -
because now we have Dove and Kirkwood platforms trying to build this
driver without RESET_CONTROLLER being set.

The problem with depending on RESET_CONTROLLER is that then these
platforms end up without their I2C controller - because there's nothing
which enables RESET_CONTROLLER in their configuration.

Since RESET_CONTROLLER is not required for those platforms, it really
should be optional - and I think the real fix is for the reset controller
support to provide stub functions.

-- 
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