linux-kernel - Re: [PATCH v2] i2c: rk3x: fix divisor calculation for SCL frequency

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Message-ID: <CAD=FV=WY=wS6P5f4BVfoyy8EWvrn9Mzh=wkOXBiEiJyQ-HNM=Q@mail.gmail.com>
Date:	Sun, 7 Sep 2014 21:15:16 -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 v2] i2c: rk3x: fix divisor calculation for SCL frequency

Addy,

On Sun, Sep 7, 2014 at 8:38 PM, Addy Ke <addy.ke@...k-chips.com> wrote:
> I2C_CLKDIV register descripted in the previous version of
> RK3x chip manual is incorrect. Plus 1 is required.
>
> The correct formula:
> - T(SCL_HIGH) = T(PCLK) * (CLKDIVH + 1) * 8
> - T(SCL_LOW) = T(PCLK) * (CLKDIVL + 1) * 8
> - (SCL Divsor) = 8 * ((CLKDIVL + 1) + (CLKDIVH + 1))
> - SCL = PCLK / (CLK Divsor)
>
> It will be updated to the latest version of chip manual.
>
> Signed-off-by: Addy Ke <addy.ke@...k-chips.com>
> ---
> changes since v1:
> - make it more cleaner, suggested by Doug Anderson
>
>  drivers/i2c/busses/i2c-rk3x.c | 11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)

Reviewed-by: Doug Anderson <dianders@...omium.org>
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