Re: [PATCH 2/2] arm: dt: Add device tree support for i2c instance 1 on exynos4 dt machine

[Tony Lindgren <tony@atomide.com>]

* G, Manjunath Kondaiah <manjugk@ti.com> [110719 09:59]:
> On Tue, Jul 19, 2011 at 2:00 AM, Grant Likely <grant.likely@secretlab.ca> wrote:
> >
> > No, the i2c bus node should still appear in the SoC .dtsi file.  If a
> > board doesn't use a particular i2c bus, then the board.dts file can
> > add a status = "disabled"; property to the i2c bus node to disable it.
> 
> that's right. I am referring to I2C slave devices. For a given SoC,
> two different
> boards can have different i2c slave devices with different slave
> address. In that case,
> it is better to have i2c child/slave nodes in board .dts file.

This is OK for now, but from bus/hwmod point of view we need to reset all
the unused devices as otherwise PM will never work properly.

Disabling each device in the board .dts file will never be done correctly
for most boards.. And on each board, probably 2/3 of the devices are unused
because of the pin limitations :)

So the disabling of unused devices should be done with a late_initcall and
controlled by kernel cmdline. We were thinking hwmod.disable=[0|1].

The late_initcall to disable unused device tree devices could also be
added later on to device tree core code.

Regards,

Tony