linux-kernel - Re: [PATCH v7 2/3] clk: introduce the common clock framework

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Date:	Mon, 19 Mar 2012 12:28:58 +0100
From:	Sascha Hauer <s.hauer@...gutronix.de>
To:	Rajendra Nayak <rnayak@...com>
Cc:	Mike Turquette <mturquette@...aro.org>,
	Russell King <linux@....linux.org.uk>,
	Paul Walmsley <paul@...an.com>,
	Linus Walleij <linus.walleij@...ricsson.com>,
	patches@...aro.org, Stephen Boyd <sboyd@...eaurora.org>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Magnus Damm <magnus.damm@...il.com>,
	linux-kernel@...r.kernel.org,
	Amit Kucheria <amit.kucheria@...aro.org>,
	Richard Zhao <richard.zhao@...aro.org>,
	Grant Likely <grant.likely@...retlab.ca>,
	Deepak Saxena <dsaxena@...aro.org>,
	Saravana Kannan <skannan@...eaurora.org>,
	Shawn Guo <shawn.guo@...escale.com>,
	linaro-dev@...ts.linaro.org,
	Jeremy Kerr <jeremy.kerr@...onical.com>,
	Arnd Bergman <arnd.bergmann@...aro.org>,
	linux-arm-kernel@...ts.infradead.org,
	Mike Turquette <mturquette@...com>
Subject: Re: [PATCH v7 2/3] clk: introduce the common clock framework

On Mon, Mar 19, 2012 at 04:52:05PM +0530, Rajendra Nayak wrote:
> Hi Mike,
> 
> >+/*
> >+ * calculate the new rates returning the topmost clock that has to be
> >+ * changed.
> >+ */
> >+static struct clk *clk_calc_new_rates(struct clk *clk, unsigned long rate)
> >+{
> >+	struct clk *top = clk;
> >+	unsigned long best_parent_rate = clk->parent->rate;
> 
> Shouldn't you check for a valid parent before dereferencing it? A
> clk_set_rate() on a root clock might throw up some issues otherwise.
>

Yes, should be checked.

> >+	unsigned long new_rate;
> >+
> >+	if (!clk->ops->round_rate&&  !(clk->flags&  CLK_SET_RATE_PARENT)) {
> >+		clk->new_rate = clk->rate;
> >+		return NULL;
> 
> So does this mean a clk_set_rate() fails for a clk which does not have
> a valid .round_rate and does not have a CLK_SET_RATE_PARENT flag set?
> I was thinking this could do a..
> 		clk->new_rate = rate;
> 		top = clk;
> 		goto out;
> ..instead.

The core should make sure that either both set_rate and round_rate are
present or none of them.

Sascha

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