Date: Mon, 16 Sep 2013 17:38:12 +0300
From: Mika Westerberg <mika.westerberg@linux.intel.com>
To: Mark Brown <broonie@kernel.org>
Cc: Kevin Hilman <khilman@linaro.org>, linux-i2c@vger.kernel.org,
        Wolfram Sang <wsa@the-dreams.de>,
        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
        linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org,
        Lv Zheng <lv.zheng@intel.com>, Aaron Lu <aaron.lu@intel.com>,
        linux-arm-kernel@lists.infradead.org,
        Dmitry Torokhov <dmitry.torokhov@gmail.com>,
        Mauro Carvalho Chehab <m.chehab@samsung.com>,
        Samuel Ortiz <sameo@linux.intel.com>, Lee Jones <lee.jones@linaro.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Liam Girdwood <lgirdwood@gmail.com>,
        Kyungmin Park <kyungmin.park@samsung.com>
Subject: Re: [PATCH v2 1/9] i2c: prepare runtime PM support for I2C client
 devices
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On Mon, Sep 16, 2013 at 11:12:49AM +0100, Mark Brown wrote:
> That's definitely an ACPI specific (probably x86 specific ACPI?)
> requirement not a generic one, on some systems it would increase power
> consumption since the controller will need to sit on while the device is
> functioning autonomously.

Yes, the ACPI 5.0 spec says that the device cannot be in higher D-state
than its parent. This is not x86 specific, though I'm not sure if this is
implemented elsewhere.

> Even though the controller power consumption is going to be minimal the
> power domain it is in may be relatively large.  Can't the power domains
> for ACPI deal with this requirement, for example by making the I2C slave
> power domains children of the controller power domain?

We'll look into this. Thanks for the suggestion.
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