Re: [PATCH 2/2] i2c/designware: Provide optional i2c bus recovery function

From: Rajeev kumar <rajeev-dlh.kumar-qxv4g6HH51o@public.gmane.org>
To: Shubhrajyoti Datta
	<omaplinuxkernel-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: Laxman Dewangan
	<ldewangan-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>,
	Viresh KUMAR <viresh.kumar-qxv4g6HH51o@public.gmane.org>,
	"khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org"
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	"ben-linux-elnMNo+KYs3YtjvyW6yDsg@public.gmane.org"
	<ben-linux-elnMNo+KYs3YtjvyW6yDsg@public.gmane.org>,
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	<w.sang-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>,
	Armando VISCONTI <armando.visconti-qxv4g6HH51o@public.gmane.org>,
	Shiraz HASHIM <shiraz.hashim-qxv4g6HH51o@public.gmane.org>,
	Vipin KUMAR <vipin.kumar-qxv4g6HH51o@public.gmane.org>,
	Deepak SIKRI <deepak.sikri-qxv4g6HH51o@public.gmane.org>,
	Vipul Kumar SAMAR <vipulkumar.samar-qxv4g6HH51o@public.gmane.org>,
	Amit VIRDI <Amit.VIRDI-qxv4g6HH51o@public.gmane.org>,
	Pratyush ANAND <pratyush.anand-qxv4g6HH51o@public.gmane.org>,
	Bhupesh SHARMA <bhupesh.sharma-qxv4g6HH51o@public.gmane.org>,
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	Bhavna YADAV <bhavna.yadav-qxv4g6HH51o@public.gmane.org>,
	Vincenzo FRASCINO
	<Vincenzo.FRASCINO-qxv4g6HH51o@public.gmane.org>,
	Mirko GARDI <mirko.gardi-qxv4g6HH51o@public.gmane.org>,
	Salvatore DE DOMINICIS
	<salvatore.dedominicis-qxv4g6HH51o@public.gmane.org>,
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	<linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
Subject: Re: [PATCH 2/2] i2c/designware: Provide optional i2c bus recovery function
Date: Mon, 27 Feb 2012 15:40:39 +0530	[thread overview]
Message-ID: <4F4B569F.3080607@st.com> (raw)
In-Reply-To: <CAM=Q2cs-nCuSmkBFtv4odbqoRJcPkXk4Rz-H=9S6RDG3Z8kcEQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>

Hello Shubhrajyoti

On 2/27/2012 2:42 PM, Shubhrajyoti Datta wrote:
> On Mon, Feb 27, 2012 at 12:57 PM, Laxman Dewangan<ldewangan-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>  wrote:
>> On Monday 27 February 2012 12:51 PM, Shubhrajyoti Datta wrote:
>>>
>>> On Fri, Feb 24, 2012 at 5:01 PM, Viresh Kumar<viresh.kumar-qxv4g6HH51o@public.gmane.org>    wrote:
>>>>
>>>> From: Vincenzo Frascino<vincenzo.frascino-qxv4g6HH51o@public.gmane.org>
>>>>
>>>> Add optional i2c_recover_bus() function to the Synopsys DesignWare I2C
>>>> adapter
>>>> driver that performs i2c bus recovery after timeout. The scope of this
>>>> routine
>>>> is to define i2c bus recovery procedure as specified in the i2c protocol
>>>> Rev. 03
>>>> section 3.16 titled "Bus clear".
>>>
>>> What do you do in the function ?
>>>
>>> Could we have it in the driver file itself?
>>>
>> I think bus recovery mechanism is to send  extra clock on SCL line by
>> toggling the pin (using gpio apis)
> You mean the SCL I didnt understand the gpio part?
>
> Why is gpio needed?
>

In some i2c controller (like synopsys) you dont have control over i2c 
data and clock lines. So clock toggling, you need to use gpio lines 
which in turns maps on sda and scl line.

For the controller in which you have control over sda and scl line there 
is not need for gpio lines. You can directly write on registers.

So to make the function more generic its better to control i2c lines 
with gpio.

~Rajeev

>   and keep watching of sda line whether it
>> becomes high or not.
>> We can put this algorithms in the some common file (i2c/algos/) and so if
>> any i2c bus driver want to use, they can use it.
>> Little background: I am working on tegra i2c controller and we have similar
>> logic in tegra-i2c driver which we want to upstream.
>> If similar function is in common place, we can use this and need not to
>> duplicating it on every bus driver.
>>
>>
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