linux-kernel - Re: [PATCH] clk: Propagate prepare and enable when reparenting orphans

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Message-ID: <20141108002334.GT4042@n2100.arm.linux.org.uk>
Date:	Sat, 8 Nov 2014 00:23:34 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Doug Anderson <dianders@...omium.org>
Cc:	Mike Turquette <mturquette@...aro.org>,
	Heiko Stuebner <heiko@...ech.de>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] clk: Propagate prepare and enable when reparenting
 orphans

On Fri, Nov 07, 2014 at 04:14:23PM -0800, Doug Anderson wrote:
> Russell,
> I guess I'm still confused.  My patch continues to be about orphans
> and I don't see the bug you are pointing to.

Ah, in which case, the question changes: how can an orphaned clock be
succesfully prepared and enabled?

Drivers expect that a clock for which clk_enable() has returned
successfully _will_ at that point be supplying the clock.  If we don't
yet know it's parent, how do we know that it will be supplying that
clock?

What about a driver calling clk_set_rate() on an orphaned clock?

>From what I can see (__clk_reparent will re-set the child's clock when
reparenting) having a driver able to claim an orphaned clock, let
alone prepare and enable it, looks rather buggy to me.

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