linux-kernel - Re: [PATCH v3 1/7] clk: divider: add flag to limit possible dividers to even numbers

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Message-ID: <CAHp75VcaNkPeUQ=OPY5F7Mqb_cM87xh8A8wUxdCgnRtfjoqoHw@mail.gmail.com>
Date:	Tue, 11 Jun 2013 14:51:56 +0300
From:	Andy Shevchenko <andy.shevchenko@...il.com>
To:	Heiko Stübner <heiko@...ech.de>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Mike Turquette <mturquette@...aro.org>,
	Seungwon Jeon <tgih.jun@...sung.com>,
	Jaehoon Chung <jh80.chung@...sung.com>,
	Chris Ball <cjb@...top.org>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <rob.herring@...xeda.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Devicetree Discuss <devicetree-discuss@...ts.ozlabs.org>,
	Russell King <linux@....linux.org.uk>,
	Arnd Bergmann <arnd@...db.de>, Olof Johansson <olof@...om.net>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
Subject: Re: [PATCH v3 1/7] clk: divider: add flag to limit possible dividers
 to even numbers

On Tue, Jun 11, 2013 at 2:29 PM, Heiko Stübner <heiko@...ech.de> wrote:
> SoCs like the Rockchip Cortex-A9 ones contain divider some clocks
> that use the regular mechanisms for storage but allow only even
> dividers and 1 to be used.
>
> Therefore add a flag that lets _is_valid_div limit the valid dividers
> to these values. _get_maxdiv is also adapted to return even values
> for the CLK_DIVIDER_ONE_BASED case.

Just one nitpick below (I'm okay with current implementation, but you
might find my proposal useful).

> --- a/drivers/clk/clk-divider.c
> +++ b/drivers/clk/clk-divider.c

> @@ -141,6 +149,8 @@ static bool _is_valid_div(struct clk_divider *divider, unsigned int div)
>                 return is_power_of_2(div);
>         if (divider->table)
>                 return _is_valid_table_div(divider->table, div);
> +       if (divider->flags & CLK_DIVIDER_EVEN && div != 1 && (div % 2) != 0)
> +               return false;
>         return true;
>  }

What if rewrite like

 if (divider->flags & CLK_DIVIDER_EVEN == 0)
 return true;

return div < 2 || div % 2 == 0;


--
With Best Regards,
Andy Shevchenko
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