linux-kernel - Re: [PATCH v2] i2c: rk3x: fix bug that cause measured high

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Date:	Tue, 2 Dec 2014 21:13:55 -0800
From:	Doug Anderson <dianders@...omium.org>
To:	Addy Ke <addy.ke@...k-chips.com>
Cc:	Wolfram Sang <wsa@...-dreams.de>,
	Max Schwarz <max.schwarz@...ine.de>,
	Heiko Stübner <heiko@...ech.de>,
	Olof Johansson <olof@...om.net>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	"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>,
	"open list:ARM/Rockchip SoC..." <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>,
	Caesar Wang <caesar.wang@...k-chips.com>,
	Shunqian Zheng <zhengsq@...k-chips.com>
Subject: Re: [PATCH v2] i2c: rk3x: fix bug that cause measured high_ns doesn't
 meet I2C spec

Addy,

On Tue, Dec 2, 2014 at 6:37 PM, Addy Ke <addy.ke@...k-chips.com> wrote:
> high_ns calculated from the low division of CLKDIV register is the sum
> of actual measured high_ns and rise_ns. The rise time which related to
> external pull-up resistor can be up to the maximum rise time in I2C spec.
>
> In my test, if external pull-up resistor is 4.7K, rise_ns is about
> 700ns. So the actual measured high_ns is about 3900ns, which is less
> than 4000ns(the minimum high_ns in I2C spec).
>
> To fix this bug, min_low_ns should include fall time and min_high_ns
> should include rise time too.
>
> This patch merged the patch that Doug submitted to chromium, which
> can get the rise and fall times for signals from the device tree.
> This allows us to more accurately calculate timings. see:
> https://chromium-review.googlesource.com/#/c/232774/
>
> Signed-off-by: Addy Ke <addy.ke@...k-chips.com>
> ---
> Changes in v2:
> - merged the patch that Doug submitted to chromium
>
>  Documentation/devicetree/bindings/i2c/i2c-rk3x.txt | 10 ++++
>  drivers/i2c/busses/i2c-rk3x.c                      | 55 +++++++++++++++-------
>  2 files changed, 47 insertions(+), 18 deletions(-)

This looks good to me.  Thank you for spinning.

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