linux-kernel - Re: [PATCH v3 7/7] i2c: bcm2835: Add support for dynamic clock

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Date:   Wed, 28 Sep 2016 14:24:36 -0700
From:   Eric Anholt <eric@...olt.net>
To:     Noralf Trønnes <noralf@...nnes.org>,
        wsa@...-dreams.de, swarren@...dotorg.org
Cc:     linux-kernel@...r.kernel.org, linux-i2c@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-rpi-kernel@...ts.infradead.org,
        Noralf Trønnes <noralf@...nnes.org>
Subject: Re: [PATCH v3 7/7] i2c: bcm2835: Add support for dynamic clock

Noralf Trønnes <noralf@...nnes.org> writes:

> Support a dynamic clock by reading the frequency and setting the
> divisor in the transfer function instead of during probe.

Is this fixing some particular case you could note in the commit
message?  As is, it makes me think that we should be using a notifier
for when the parent clock (that's the one I assume you're talking about
being dynamic) changes.  But maybe you're working around a variable VPU
clock being set by the firmware, because we don't have a notifier for
it?

I'm a bit worried because I think this is going to be pretty expensive
to be doing per transfer.

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