From mboxrd@z Thu Jan  1 00:00:00 1970
From: bilhuang@nvidia.com (Bill Huang)
Date: Thu, 14 Mar 2013 02:28:07 -0700
Subject: [RFC 1/1] clk: Add notifier support in
 clk_prepare_enable/clk_disable_unprepare
In-Reply-To: <20130314092132.GE18519@tbergstrom-lnx.Nvidia.com>
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 <1363153204.3311.14.camel@bilhuang-vm1> <5140C12A.4060900@wwwdotorg.org>
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Message-ID: <1363253287.3311.32.camel@bilhuang-vm1>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Thu, 2013-03-14 at 17:21 +0800, Peter De Schrijver wrote:
> On Thu, Mar 14, 2013 at 03:15:11AM +0100, Bill Huang wrote:
> 
> > I don't think deferring will work either, considering the usage of DVFS,
> > device voltage is tightly coupled with frequency, when clock rate is
> > about to increase, we have to boost voltage first and we can lower the
> > voltage after the clock rate has decreased. All the above sequence have
> > to be guaranteed or you might crash, so deferring not only make thing
> > complicated in controlling the order but also hurt performance.
> 
> But we could use notifiers in clk_prepare/clk_unprepare to set the voltage no?
> As clk_prepare/clk_unprepare have to be called before clk_enable or after
> clk_disable, the voltage can be raised to a safe level, before the clock
> becomes active.

Thanks Peter, actually I'm just about to propose my v2 RFC which add
notifier in clk_prepare/clk_unprepare.
> 
> Cheers,
> 
> Peter.