linux-kernel - Re: [patch 2.6.28-rc2] atmel_serial: keep clock off when it's not needed

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Message-ID: <20081028124526.6b9ccdf5@hskinnemo-gx745.norway.atmel.com>
Date:	Tue, 28 Oct 2008 12:45:26 +0100
From:	Haavard Skinnemoen <haavard.skinnemoen@...el.com>
To:	David Brownell <david-b@...bell.net>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Haavard Skinnemoen <hskinnemoen@...el.com>,
	Nicolas Ferre <nicolas.ferre@....atmel.com>,
	Andrew Victor <linux@...im.org.za>
Subject: Re: [patch 2.6.28-rc2] atmel_serial: keep clock off when it's not
 needed

David Brownell <david-b@...bell.net> wrote:
> From: David Brownell <dbrownell@...rs.sourceforge.net>
> 
> The atmel_serial driver is mismanaging its clock by leaving it on
> at all times ... the whole point of clock management is to leave
> it off unless it's actively needed, which conserves power!!
> 
> Signed-off-by: David Brownell <dbrownell@...rs.sourceforge.net>

Hmm...the only remaining clk_enable() is in atmel_serial_pm(). Is that
really enough?

It looks like the serial core calls ->pm() to power the port up before
doing anything that might touch the registers, but I can't see that the
console layer does the same thing...

Haavard
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