linux-kernel - Re: [5/5] i2c: davinci: use ICPFUNC to toggle I2C as gpio for bus recovery

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Date:	Mon, 24 Nov 2014 19:13:06 +0100
From:	Mike Looijmans <info@...osoftware.com>
To:	Grygorii Strashko <grygorii.strashko@...com>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
CC:	Wolfram Sang <wsa@...-dreams.de>, linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org, Sekhar Nori <nsekhar@...com>,
	Kevin Hilman <khilman@...prootsystems.com>,
	Santosh Shilimkar <ssantosh@...nel.org>,
	Murali Karicheri <m-karicheri2@...com>,
	Ben Gardiner <bengardiner@...ometrics.ca>,
	Mike Looijmans <milo-software@...rs.sourceforge.net>
Subject: Re: [5/5] i2c: davinci: use ICPFUNC to toggle I2C as gpio for bus
 recovery

On 24-11-2014 14:15, Grygorii Strashko wrote:
> Hi Uwe,
> On 11/23/2014 07:04 PM, Uwe Kleine-König wrote:
>> On Thu, Nov 20, 2014 at 12:03:08PM +0200, Grygorii Strashko wrote:
>>> @@ -664,6 +759,7 @@ static int davinci_i2c_probe(struct platform_device *pdev)
>>>    		if (!of_property_read_u32(pdev->dev.of_node, "clock-frequency",
>>>    			&prop))
>>>    			dev->pdata->bus_freq = prop / 1000;
>>> +		dev->pdata->has_pfunc = true;
>> I don't understand this. Why does this ICPFUNC recovery work if the bus
>> is probed by oftree, but doesn't if not?
> I've mentioned this in commit message:
>   Allow platforms to indicate the presence of the ICPFUNC registers with a has_pfunc
>   platform data flag and enable this mode for platforms which supports DT (da850 and
>   Keystone 2 are two SoCs which support DT now and they also support ICPFUNC registers).
>
> I'll add proper comment here.

Just thinking: What happens if you try to use the ICPFUNC registers on 
platforms that don't support it? If the answer is "nothing bad", then 
you might as well assume that if the platform doesn't specify its own 
GPIOs, you can always try using the ICPFUNC registers to shake the I2C 
bus. Better to try and fail than to never try at all...

>
>>>    	} else if (!dev->pdata) {
>>>    		dev->pdata = &davinci_i2c_platform_data_default;
>>>    	}
>>> @@ -705,7 +801,9 @@ static int davinci_i2c_probe(struct platform_device *pdev)
>>>    	adap->timeout = DAVINCI_I2C_TIMEOUT;
>>>    	adap->dev.of_node = pdev->dev.of_node;
>>>    
>>> -	if (dev->pdata->scl_pin) {
>>> +	if (dev->pdata->has_pfunc)
>>> +		adap->bus_recovery_info = &davinci_i2c_scl_recovery_info;
>>> +	else if (dev->pdata->scl_pin) {
>>>    		adap->bus_recovery_info = &davinci_i2c_gpio_recovery_info;
>>>    		adap->bus_recovery_info->scl_gpio = dev->pdata->scl_pin;
>>>    		adap->bus_recovery_info->sda_gpio = dev->pdata->sda_pin;
>>> diff --git a/include/linux/platform_data/i2c-davinci.h b/include/linux/platform_data/i2c-davinci.h
>>> index 2312d19..89fd347 100644
>>> --- a/include/linux/platform_data/i2c-davinci.h
>>> +++ b/include/linux/platform_data/i2c-davinci.h
>>> @@ -18,6 +18,7 @@ struct davinci_i2c_platform_data {
>>>    	unsigned int	bus_delay;	/* post-transaction delay (usec) */
>>>    	unsigned int    sda_pin;        /* GPIO pin ID to use for SDA */
>>>    	unsigned int    scl_pin;        /* GPIO pin ID to use for SCL */
>>> +	bool		has_pfunc;	/*chip has a ICPFUNC register */
>> Space after /* please
>>
> regards,
> -grygorii
>
>
>

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