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

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Message-ID: <5710DA28.6010104@rock-chips.com>
Date:	Fri, 15 Apr 2016 20:10:16 +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 2016/4/15 2:48, Wolfram Sang 写道:
>> + - input-clk-rate : frequency rate of function clock used(in Hz). If omitted,
>> +	the default clock rate is used. It is just used at rk3399 soc.
> Why is this needed? Why don't we simply use the default or calculate the
> best value somehow?
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.

>> + * @t_calc: Caculated rk3x private timings  that would
>> + * be written into regs
> double space
>