Subject: [PATCHv5 1/3] OMAP: I2C: Reset support

From: [email-masked] (Shubhrajyoti)
Date: Thu, 04 Aug 2011 11:55:12 +0530

On Wednesday 03 August 2011 04:53 AM, Kevin Hilman wrote:
> Shubhrajyoti D<[email-masked]>  writes:
>
>>   Under some error conditions the i2c  driver may do a reset.
>    ^                                    ^
> minor: extra whitespace
>
>>   Adding a reset field and support in the platform.
> s/platform/device-specific code/
>
Yes will fix these.
>> Signed-off-by: Shubhrajyoti D<[email-masked]>
> That being said, omap_device_shutdown() should already do a clean
> shutdown + reset for you, and i2c-omap.h already has a pointer for
> ->device_shutdown() so a new device_reset() should not be needed.
>
> IOW, simply adding pdata->device_shutdown = omap_device_shutdown()
> should work.
i2C has a special reset sequence ie Disable -> reset -> enable -> Poll 
on reset done.
This function is implemented in omap_i2c_reset. The

omap_hwmod_reset calls ->  _reset

which calls ocp_softrest  or custom reset if it is present.The latter is 
true for I2C.

However I see that

omap_device_shutdown ->  _assert_hardreset However for I2c there doesnt seem to be a HW reset line.

Am I missing something?

> Kevin
>
>> ---
>>   arch/arm/plat-omap/i2c.c |   18 ++++++++++++++++++
>>   include/linux/i2c-omap.h |    1 +
>>   2 files changed, 19 insertions(+), 0 deletions(-)
>>
>> diff --git a/arch/arm/plat-omap/i2c.c b/arch/arm/plat-omap/i2c.c
>> index 2388b8e..be36cac 100644
>> --- a/arch/arm/plat-omap/i2c.c
>> +++ b/arch/arm/plat-omap/i2c.c
>> @@ -146,6 +146,22 @@ static struct omap_device_pm_latency omap_i2c_latency[] = {
>>   		.flags			= OMAP_DEVICE_LATENCY_AUTO_ADJUST,
>>   	},
>>   };
>> +/**
>> + * omap2_i2c_reset - reset the omap i2c module.
>> + * @dev: struct device*
>> + */
>> +
>> +static int omap2_i2c_reset(struct device *dev)
>> +{
>> +	int r = 0;
>> +	struct platform_device *pdev = to_platform_device(dev);
>> +	struct omap_device *odev = to_omap_device(pdev);
>> +	struct omap_hwmod *oh;
>> +
>> +	oh = odev->hwmods[0];
>> +	r = omap_hwmod_reset(oh);
>> +	return r;
>> +}
>>
>>   static inline int omap2_i2c_add_bus(int bus_id)
>>   {
>> @@ -187,6 +203,8 @@ static inline int omap2_i2c_add_bus(int bus_id)
>>   	 */
>>   	if (cpu_is_omap34xx())
>>   		pdata->set_mpu_wkup_lat = omap_pm_set_max_mpu_wakeup_lat_compat;
>> +
>> +	pdata->device_reset = omap2_i2c_reset;
>>   	od = omap_device_build(name, bus_id, oh, pdata,
>>   			sizeof(struct omap_i2c_bus_platform_data),
>>   			omap_i2c_latency, ARRAY_SIZE(omap_i2c_latency), 0);
>> diff --git a/include/linux/i2c-omap.h b/include/linux/i2c-omap.h
>> index 98ae49b..8aa91b6 100644
>> --- a/include/linux/i2c-omap.h
>> +++ b/include/linux/i2c-omap.h
>> @@ -38,6 +38,7 @@ struct omap_i2c_bus_platform_data {
>>   	int		(*device_enable) (struct platform_device *pdev);
>>   	int		(*device_shutdown) (struct platform_device *pdev);
>>   	int		(*device_idle) (struct platform_device *pdev);
>> +	int		(*device_reset) (struct device *dev);
>>   };
>>
>>   #endif