linux-kernel - Re: [PATCH v5] i2c: rk3x: fix bug that cause measured high

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Date:	Tue, 13 Jan 2015 12:42:37 +0100
From:	Wolfram Sang <wsa@...-dreams.de>
To:	Addy Ke <addy.ke@...k-chips.com>
Cc:	max.schwarz@...ine.de, heiko@...ech.de, olof@...om.net,
	dianders@...omium.org, robh+dt@...nel.org, pawel.moll@....com,
	ijc+devicetree@...lion.org.uk, galak@...eaurora.org,
	u.kleine-koenig@...gutronix.de, linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-rockchip@...ts.infradead.org, cf@...k-chips.com,
	xjq@...k-chips.com, huangtao@...k-chips.com, zyw@...k-chips.com,
	yzq@...k-chips.com, hj@...k-chips.com, kever.yang@...k-chips.com,
	hl@...k-chips.com, caesar.wang@...k-chips.com,
	zhengsq@...k-chips.com
Subject: Re: [PATCH v5] i2c: rk3x: fix bug that cause measured high_ns
 doesn't meet I2C specification

On Thu, Dec 11, 2014 at 07:02:40PM +0800, Addy Ke wrote:
> The number of clock cycles to be written into the CLKDIV register
> that determines the I2C clk high phase includes the rise time.
> So to meet the timing requirements defined in the I2C specification
> which defines the minimal time SCL has to be high, the rise time
> has to taken into account. The same applies to the low phase with
> falling time.
> 
> In my test on RK3288-Pink2 board, which is not an upstream board yet,
> if external pull-up resistor is 4.7K, rise_ns is about 700ns.
> So the measured high_ns is about 3900ns, which is less than 4000ns
> (the minimum high_ns in I2C specification for Standard-mode).
> 
> To fix this bug min_low_ns should include fall time and min_high_ns
> should include rise time.
> 
> This patch merged the patch from chromium project 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>

Applied to for-next, thanks!

I fixed the typo Doug mentioned.

Please send new patches as seperate threads, not as a reply to the old
patch.


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