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

[Laxman Dewangan <ldewangan-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>]

On Monday 27 February 2012 01:40 PM, Rajeev kumar wrote:
> On 2/27/2012 12:57 PM, Laxman Dewangan 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) 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.
>>
> I agreed with Laxman, as this is the protocol issue and so it should not
> be in each individual driver. It should be the part of framework
> itself. We need to implement something like
> drivers/i2c/busses/i2c-gpio.c.  We need to investigate more on it.
>
I am thinking to put this in drivers/i2c/busses/bus_recovery_gpio.c. 
This will provide only one function and config variable for this code 
can be selected from different driver by select option. it will not be 
enabled as independent driver. Similar to regmap_i2c or regmap_spi which 
is selected through select in kconfig

The function should take the gpio number and gpio flags for scl and sda, 
bus freq and number of clock to be sent.
All gpio related apis should be called on .c file which is implemented.

How bus driver gets the corresponding gpio number is specific to bus 
driver but they need to pass all the information through arguments.



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