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

Rajeev kumar <rajeev-dlh.kumar@xxxxxx> · Mon, 27 Feb 2012 15:40:39 +0530

Hello Shubhrajyoti

On 2/27/2012 2:42 PM, Shubhrajyoti Datta wrote:

On Mon, Feb 27, 2012 at 12:57 PM, Laxman Dewangan<ldewangan@xxxxxxxxxx>  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@xxxxxx>    wrote:

From: Vincenzo Frascino<vincenzo.frascino@xxxxxx>

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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