linux-kernel - Re: [PATCH v4 2/6] Documentation: common clk API

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Date:	Thu, 5 Jan 2012 12:04:44 -0800
From:	"Turquette, Mike" <mturquette@...com>
To:	Mike Turquette <mturquette@...aro.org>, linux@....linux.org.uk,
	linux-kernel@...r.kernel.org, linux-omap@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, jeremy.kerr@...onical.com,
	paul@...an.com, broonie@...nsource.wolfsonmicro.com,
	tglx@...utronix.de, linus.walleij@...ricsson.com,
	dsaxena@...aro.org, patches@...aro.org,
	linaro-dev@...ts.linaro.org, grant.likely@...retlab.ca,
	sboyd@...cinc.com, shawn.guo@...escale.com, skannan@...cinc.com,
	magnus.damm@...il.com, arnd.bergmann@...aro.org,
	eric.miao@...aro.org, richard.zhao@...aro.org, mturquette@...com,
	andrew@...n.ch
Subject: Re: [PATCH v4 2/6] Documentation: common clk API

On Thu, Jan 5, 2012 at 6:31 AM, Amit Kucheria <amit.kucheria@...aro.org> wrote:
> Tiny, tiny typo...
>
> On 11 Dec 13, Mike Turquette wrote:
>
>> +clk_set_rate deserves a special mention because it is more complex than
>> +the other operations.  There are three key concepts to the common
>> +clk_set_rate implementation:
>> +
>> +1) recursively traversing up the clk tree and changing clk rates, one
>> +parent at a time, if each clk allows it
>> +2) failing to change rate if the clk is enabled and must only change
>> +rates while disabled
>> +3) using clk rate change notifiers to allow devices to handle dynamic
>> +rate changes for clks which do support changing rates while enabled
>> +
>> +For the simple, non-recursive case the call graph looks like:
>> +
>> +clk_set_rate(clk, rate);
>> +     __clk_set_rate(clk, rate);
>> +             clk->round_rate(clk, rate *parent_rate);
>                                      ^^^^^^^^
>
> need a comma here? The next sentence kept me busy for 5 mins.

Thanks, will fix in next submission (along with general rework of
messy documentation).

Mike

>
>> +             clk->set_rate(clk, rate);
>> +
>> +You might be wondering what that third paramater in .round_rate is.  If
>> +a clk supports the CLK_PARENT_SET_RATE flag then that enables it's
>> +hardware-specific .round_rate function to provide a new rate that the
>> +parent should transition to.  For example, imagine a rate-adjustable clk
>> +A that is the parent of clk B, which has a fixed divider of 2.
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