linux-kernel - Re: [PATCH v5 2/2] i2c: rk3x: add i2c support for rk3399 soc

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Message-ID: <5714DE02.3040304@rock-chips.com>
Date:	Mon, 18 Apr 2016 21:15:46 +0800
From:	"David.Wu" <david.wu@...k-chips.com>
To:	Wolfram Sang <wsa@...-dreams.de>
Cc:	heiko@...ech.de, dianders@...omium.org, andy.shevchenko@...il.com,
	huangtao@...k-chips.com, hl@...k-chips.com, xjq@...k-chips.com,
	zyw@...k-chips.com, cf@...k-chips.com,
	linux-arm-kernel@...ts.infradead.org,
	linux-rockchip@...ts.infradead.org, linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org, David Wu <wdc@...k-chips.com>
Subject: Re: [PATCH v5 2/2] i2c: rk3x: add i2c support for rk3399 soc

Hi Wolfram，

在 2016/4/16 1:58, Wolfram Sang 写道:
>> The default frequency rate of function clock is 50M Hz, it can match
>> F/S mode, but HS mode not. If use default rate 50M to get 1.7M
>> scl-frequency rate , we could not get accurately 1.7M frequecy rate.
>> The input-clk-rate is more higher, we get more accurately
>> scl-frequency rate,  as 200M is a suitable input-clk-rate.
>>
>> If 200M was used for F/S mode, it would increase power consumption, so
>> add a option that could be configured from DT.
> If I understand you correctly, couldn't you use clk_set_rate() depending
> on the desired scl frequency which is already described in DT as
> clock-frequency?

Yeap, the default input clock rate is too low for HS mode, and it 's 
flexible that
we get it from DT.