From mboxrd@z Thu Jan  1 00:00:00 1970
From: Wolfram Sang <wsa@the-dreams.de>
Subject: Re: [PATCH] i2c: s3c2410: remove superfluous runtime PM calls
Date: Sat, 19 Dec 2015 11:50:31 +0100
Message-ID: <20151219105030.GA2571@katana>
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To: Sylwester Nawrocki <s.nawrocki@samsung.com>
Cc: linux-i2c@vger.kernel.org, linux-pm@vger.kernel.org, Charles Keepax <ckeepax@opensource.wolfsonmicro.com>, Lars-Peter Clausen <lars@metafoo.de>, Krzysztof Kozlowski <k.kozlowski@samsung.com>
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Hi,

> > Since commit 6ada5c1e1b077a ("i2c: Mark adapter devices with
> > pm_runtime_no_callbacks"), runtime PM on adapters turned into a no-op.
> > So, we can remove these calls.
>=20
> Won't this break i2c client devices that use runtime PM? Not sure
> if any cases of such client exist now, I'll try to find some time
> to test this change.

Thanks, much appreciated.

> IIRC client's pm_runtime* calls return error if their parent device's
> runtime PM is not enabled. Also enabling runtime PM on the i2c adapter
> allows propagating runtime PM calls up to its parent - the i2c
> controller platform device.

I was thinking the PM core would take care of that. Grepping for
other users of pm_runtime_no_callbacks(), I see that most but not all
use pm_runtime_enable() on the device, too.

Asking linux-pm for help here: If we want to support RuntimePM for I2C
clients, do we need to enable RuntimePM on the logical I2C adapter
device (the bus master) which is already marked using
pm_runtime_no_callbacks?

> Perhaps we could just enable/disable adapter's runtime PM in i2c core.

That would be the proper place to do it, as I see it.

Thanks,

   Wolfram


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