linux-kernel - Re: [PATCH] gpu: host1x: clk_round_rate() can return a zero upon error

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Date:	Tue, 10 Dec 2013 23:55:49 -0800
From:	Paul Walmsley <pwalmsley@...dia.com>
To:	Sascha Hauer <s.hauer@...gutronix.de>
CC:	Mikko Perttunen <mperttunen@...dia.com>,
	Arto Merilainen <amerilainen@...dia.com>,
	Thierry Reding <thierry.reding@...il.com>,
	Terje Bergstrom <tbergstrom@...dia.com>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH] gpu: host1x: clk_round_rate() can return a zero upon
 error

On 12/10/2013 11:51 PM, Sascha Hauer wrote:
> On Mon, Dec 09, 2013 at 06:00:12PM -0800, Paul Walmsley wrote:
>> Treat both negative and zero return values from clk_round_rate() as
>> errors.  This is needed since subsequent patches will convert
>> clk_round_rate()'s return value to be an unsigned type, rather than a
>> signed type, since some clock sources can generate rates higher than
>> (2^31)-1 Hz.
>>
>> Eventually, when calling clk_round_rate(), only a return value of zero
>> will be considered a error.  All other values will be considered valid
>> rates.  The comparison against values less than 0 is kept to preserve
>> the correct behavior in the meantime.
> Shouldn't it be an error when the result is not within sensible limits
> instead? What do you do with a rate of 1Hz?

It's up to the caller of clk_round_rate() to decide what doesn't make 
sense for its use-case.  The caller can certainly react to non-zero 
rates as it likes.

The 0 return code (and the previous negative return values that were 
used previously) are just intended for the clock framework to signal 
explicit errors encountered during clk_round_rate()'s execution.

- Paul
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