linux-kernel - Re: [PATCH v9 3/3] clk: Add floor and ceiling constraints to clock rates

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Date:	Tue, 20 Jan 2015 14:04:10 +0100
From:	Tomeu Vizoso <tomeu.vizoso@...labora.com>
To:	Stephen Boyd <sboyd@...eaurora.org>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Mike Turquette <mturquette@...aro.org>,
	Javier Martinez Canillas <javier.martinez@...labora.co.uk>,
	Jonathan Corbet <corbet@....net>,
	Tony Lindgren <tony@...mide.com>,
	Russell King <linux@....linux.org.uk>,
	Ralf Baechle <ralf@...ux-mips.org>,
	Boris Brezillon <boris.brezillon@...e-electrons.com>,
	Emilio López <emilio@...pez.com.ar>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Tero Kristo <t-kristo@...com>,
	Manuel Lauss <manuel.lauss@...il.com>,
	Alex Elder <elder@...aro.org>,
	Matt Porter <mporter@...aro.org>,
	Zhangfei Gao <zhangfei.gao@...aro.org>,
	Haojian Zhuang <haojian.zhuang@...aro.org>,
	Jaehoon Chung <jh80.chung@...sung.com>,
	Bintian Wang <bintian.wang@...wei.com>,
	Chao Xie <chao.xie@...vell.com>, linux-doc@...r.kernel.org,
	linux-omap@...r.kernel.org,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>, linux-mips@...ux-mips.org
Subject: Re: [PATCH v9 3/3] clk: Add floor and ceiling constraints to clock rates

On 20 January 2015 at 01:00, Stephen Boyd <sboyd@...eaurora.org> wrote:
> On 01/19, Tomeu Vizoso wrote:
>> Adds a way for clock consumers to set maximum and minimum rates. This can be
>> used for thermal drivers to set ceiling rates, or by misc. drivers to set
>> floor rates to assure a minimum performance level.
>>
>> Changes the signature of the determine_rate callback by adding the
>> parameters floor_rate and ceiling_rate.
>
> Commit text needs the s/floor/min and s/ceiling/max treatment
> too.
>
>>
>> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
>> index f2a1ff3..55b3124 100644
>> --- a/drivers/clk/clk.c
>> +++ b/drivers/clk/clk.c
>> @@ -1026,6 +1051,28 @@ static unsigned long clk_core_round_rate_nolock(struct clk_core *clk,
>>       else
>>               return clk->rate;
>>  }
>> +unsigned long __clk_determine_rate(struct clk_hw *hw,
>> +                                unsigned long rate,
>> +                                unsigned long min_rate,
>> +                                unsigned long max_rate)
>> +{
>> +     unsigned long parent_rate = 0;
>> +     struct clk_core *core = hw->core;
>> +     struct clk_hw *parent_hw;
>> +
>> +     if (!core->ops->determine_rate)
>> +             return 0;
>> +
>> +     if (core->parent) {
>> +             parent_rate = core->parent->rate;
>> +             parent_hw = core->parent->hw;
>> +     }
>> +
>> +     return core->ops->determine_rate(core->hw, rate,
>> +                                     min_rate, max_rate,
>> +                                     &parent_rate, &parent_hw);
>> +}
>> +EXPORT_SYMBOL_GPL(__clk_determine_rate);
>
> Maybe I misled you with the API name. I was thinking more along
> the lines of clk_round_rate() and this new function ending up
> calling clk_core_round_rate(), but clk_round_rate() would call it
> with whatever range the clock is constrained to while this new
> function would allow driver authors to specify the range. It
> should be easy enough to add min/max to clk_core_round_rate()
> given that it's a private API in this file.

Yeah, I wasn't sure whether it made sense for __clk_determine_rate to
have the fallbacks because any caller would need to have checked that
the clock implementation supports determine_rate and is aware of the
rate constraints.

As long as people don't get confused, I'm fine with any of the possibilities.

Regards,

Tomeu

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