linux-kernel - Re: [PATCH] i2c: rk3x: fix divisor calculation for SCL frequency

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Message-ID: <CAD=FV=WwCTRh44jTvTZoeFFACmWKeGyu=zWb1=BeimGMuT9r2Q@mail.gmail.com>
Date:	Fri, 5 Sep 2014 08:20:23 -0700
From:	Doug Anderson <dianders@...omium.org>
To:	addy ke <addy.ke@...k-chips.com>
Cc:	Wolfram Sang <wsa@...-dreams.de>, max.schwarz@...ine.de,
	Heiko Stübner <heiko@...ech.de>,
	Olof Johansson <olof@...om.net>,
	"linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	linux-rockchip@...ts.infradead.org, Eddie Cai <cf@...k-chips.com>,
	Jianqun Xu <xjq@...k-chips.com>,
	Tao Huang <huangtao@...k-chips.com>,
	Chris <zyw@...k-chips.com>,
	姚智情 <yzq@...k-chips.com>,
	han jiang <hj@...k-chips.com>,
	Kever Yang <kever.yang@...k-chips.com>,
	Lin Huang <hl@...k-chips.com>,
	晓腾王 <caesar.wang@...k-chips.com>,
	Shunqian Zheng <zhengsq@...k-chips.com>
Subject: Re: [PATCH] i2c: rk3x: fix divisor calculation for SCL frequency

Addy,

On Fri, Sep 5, 2014 at 3:17 AM, addy ke <addy.ke@...k-chips.com> wrote:

> The following modifications is reasonable?
>
> static void rk3x_i2c_set_scl_rate(struct rk3x_i2c *i2c, unsigned long scl_rate)
> {
>         unsigned long i2c_rate = clk_get_rate(i2c->clk);
>         unsigned int div;
>
>         /* set DIV = DIVH = DIVL
>          * SCL rate = (clk rate) / (8 * (DIVH + 1 + DIVL + 1))
>          *          = (clk rate) / (16 * (DIV + 1))
>          */
>         div = DIV_ROUND_UP(i2c_rate, scl_rate * 16) - 1;
>
>         i2c_writel(i2c, (div << 16) | (div & 0xffff), REG_CLKDIV);
> }

Yes, that looks much cleaner and is a nice solution, thanks!  Can you
send up a new patch version?

-Doug
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