Re: [PATCH v2 3/3] iio: light: opt3001: enable operation w/o IRQ

[Jonathan Cameron <jic23@kernel.org>]

On 29/01/16 18:01, Andreas Dannenberg wrote:
> On Sat, Jan 16, 2016 at 05:14:38PM +0100, Alexander Koch wrote:
>> Enable operation of the TI OPT3001 light sensor without having an
>> interrupt line available to connect the INT pin to.
>>
>> In this operation mode, we issue a conversion request and simply wait
>> for the conversion time available as timeout value, determined from
>> integration time configuration and the worst-case time given in the data
>> sheet (sect. 6.5, table on p. 5):
>>
>>   short integration time (100ms): 110ms + 3ms = 113ms
>>    long integration time (800ms): 880ms + 3ms = 883ms
>>
>> This change is transparent as behaviour defaults to using the interrupt
>> method if an interrupt no. is configured via device tree. Interrupt-less
>> operation mode is performed when no valid interrupt no. is given.
>>
>> Signed-off-by: Alexander Koch <mail@alexanderkoch.net>
>> Signed-off-by: Michael Hornung <mhornung.linux@gmail.com>
> 
> Tested-by: Andreas Dannenberg <dannenberg@ti.com>
> 
> I tested both interrupt mode and non-interrupt mode using a BeagleBone
> Black. Works like a champ. Also the hard-coded integration "wait" times
> look good.
> 
Thanks, I have added your tested-by to the patches.

Jonathan
> 
> --
> Andreas Dannenberg
> Texas Instruments Inc
> 
> 
>> ---
>>  drivers/iio/light/opt3001.c | 137 ++++++++++++++++++++++++++++++--------------
>>  1 file changed, 95 insertions(+), 42 deletions(-)
>>
>> diff --git a/drivers/iio/light/opt3001.c b/drivers/iio/light/opt3001.c
>> index b05c484..2a2340d 100644
>> --- a/drivers/iio/light/opt3001.c
>> +++ b/drivers/iio/light/opt3001.c
>> @@ -70,9 +70,12 @@
>>  
>>  /*
>>   * Time to wait for conversion result to be ready. The device datasheet
>> - * worst-case max value is 880ms. Add some slack to be on the safe side.
>> + * sect. 6.5 states results are ready after total integration time plus 3ms.
>> + * This results in worst-case max values of 113ms or 883ms, respectively.
>> + * Add some slack to be on the safe side.
>>   */
>> -#define OPT3001_RESULT_READY_TIMEOUT	msecs_to_jiffies(1000)
>> +#define OPT3001_RESULT_READY_SHORT	150
>> +#define OPT3001_RESULT_READY_LONG	1000
>>  
>>  struct opt3001 {
>>  	struct i2c_client	*client;
>> @@ -92,6 +95,8 @@ struct opt3001 {
>>  
>>  	u8			high_thresh_exp;
>>  	u8			low_thresh_exp;
>> +
>> +	bool			use_irq;
>>  };
>>  
>>  struct opt3001_scale {
>> @@ -230,26 +235,30 @@ static int opt3001_get_lux(struct opt3001 *opt, int *val, int *val2)
>>  	u16 reg;
>>  	u8 exponent;
>>  	u16 value;
>> +	long timeout;
>>  
>> -	/*
>> -	 * Enable the end-of-conversion interrupt mechanism. Note that doing
>> -	 * so will overwrite the low-level limit value however we will restore
>> -	 * this value later on.
>> -	 */
>> -	ret = i2c_smbus_write_word_swapped(opt->client, OPT3001_LOW_LIMIT,
>> -			OPT3001_LOW_LIMIT_EOC_ENABLE);
>> -	if (ret < 0) {
>> -		dev_err(opt->dev, "failed to write register %02x\n",
>> -				OPT3001_LOW_LIMIT);
>> -		return ret;
>> +	if (opt->use_irq) {
>> +		/*
>> +		 * Enable the end-of-conversion interrupt mechanism. Note that
>> +		 * doing so will overwrite the low-level limit value however we
>> +		 * will restore this value later on.
>> +		 */
>> +		ret = i2c_smbus_write_word_swapped(opt->client,
>> +					OPT3001_LOW_LIMIT,
>> +					OPT3001_LOW_LIMIT_EOC_ENABLE);
>> +		if (ret < 0) {
>> +			dev_err(opt->dev, "failed to write register %02x\n",
>> +					OPT3001_LOW_LIMIT);
>> +			return ret;
>> +		}
>> +
>> +		/* Allow IRQ to access the device despite lock being set */
>> +		opt->ok_to_ignore_lock = true;
>>  	}
>>  
>> -	/* Reset data-ready indicator flag (will be set in the IRQ routine) */
>> +	/* Reset data-ready indicator flag */
>>  	opt->result_ready = false;
>>  
>> -	/* Allow IRQ to access the device despite lock being set */
>> -	opt->ok_to_ignore_lock = true;
>> -
>>  	/* Configure for single-conversion mode and start a new conversion */
>>  	ret = i2c_smbus_read_word_swapped(opt->client, OPT3001_CONFIGURATION);
>>  	if (ret < 0) {
>> @@ -269,32 +278,69 @@ static int opt3001_get_lux(struct opt3001 *opt, int *val, int *val2)
>>  		goto err;
>>  	}
>>  
>> -	/* Wait for the IRQ to indicate the conversion is complete */
>> -	ret = wait_event_timeout(opt->result_ready_queue, opt->result_ready,
>> -			OPT3001_RESULT_READY_TIMEOUT);
>> +	if (opt->use_irq) {
>> +		/* Wait for the IRQ to indicate the conversion is complete */
>> +		ret = wait_event_timeout(opt->result_ready_queue,
>> +				opt->result_ready,
>> +				msecs_to_jiffies(OPT3001_RESULT_READY_LONG));
>> +	} else {
>> +		/* Sleep for result ready time */
>> +		timeout = (opt->int_time == OPT3001_INT_TIME_SHORT) ?
>> +			OPT3001_RESULT_READY_SHORT : OPT3001_RESULT_READY_LONG;
>> +		msleep(timeout);
>> +
>> +		/* Check result ready flag */
>> +		ret = i2c_smbus_read_word_swapped(opt->client,
>> +						  OPT3001_CONFIGURATION);
>> +		if (ret < 0) {
>> +			dev_err(opt->dev, "failed to read register %02x\n",
>> +				OPT3001_CONFIGURATION);
>> +			goto err;
>> +		}
>> +
>> +		if (!(ret & OPT3001_CONFIGURATION_CRF)) {
>> +			ret = -ETIMEDOUT;
>> +			goto err;
>> +		}
>> +
>> +		/* Obtain value */
>> +		ret = i2c_smbus_read_word_swapped(opt->client, OPT3001_RESULT);
>> +		if (ret < 0) {
>> +			dev_err(opt->dev, "failed to read register %02x\n",
>> +				OPT3001_RESULT);
>> +			goto err;
>> +		}
>> +		opt->result = ret;
>> +		opt->result_ready = true;
>> +	}
>>  
>>  err:
>> -	/* Disallow IRQ to access the device while lock is active */
>> -	opt->ok_to_ignore_lock = false;
>> +	if (opt->use_irq)
>> +		/* Disallow IRQ to access the device while lock is active */
>> +		opt->ok_to_ignore_lock = false;
>>  
>>  	if (ret == 0)
>>  		return -ETIMEDOUT;
>>  	else if (ret < 0)
>>  		return ret;
>>  
>> -	/*
>> -	 * Disable the end-of-conversion interrupt mechanism by restoring the
>> -	 * low-level limit value (clearing OPT3001_LOW_LIMIT_EOC_ENABLE). Note
>> -	 * that selectively clearing those enable bits would affect the actual
>> -	 * limit value due to bit-overlap and therefore can't be done.
>> -	 */
>> -	value = (opt->low_thresh_exp << 12) | opt->low_thresh_mantissa;
>> -	ret = i2c_smbus_write_word_swapped(opt->client, OPT3001_LOW_LIMIT,
>> -			value);
>> -	if (ret < 0) {
>> -		dev_err(opt->dev, "failed to write register %02x\n",
>> -				OPT3001_LOW_LIMIT);
>> -		return ret;
>> +	if (opt->use_irq) {
>> +		/*
>> +		 * Disable the end-of-conversion interrupt mechanism by
>> +		 * restoring the low-level limit value (clearing
>> +		 * OPT3001_LOW_LIMIT_EOC_ENABLE). Note that selectively clearing
>> +		 * those enable bits would affect the actual limit value due to
>> +		 * bit-overlap and therefore can't be done.
>> +		 */
>> +		value = (opt->low_thresh_exp << 12) | opt->low_thresh_mantissa;
>> +		ret = i2c_smbus_write_word_swapped(opt->client,
>> +						   OPT3001_LOW_LIMIT,
>> +						   value);
>> +		if (ret < 0) {
>> +			dev_err(opt->dev, "failed to write register %02x\n",
>> +					OPT3001_LOW_LIMIT);
>> +			return ret;
>> +		}
>>  	}
>>  
>>  	exponent = OPT3001_REG_EXPONENT(opt->result);
>> @@ -736,12 +782,18 @@ static int opt3001_probe(struct i2c_client *client,
>>  		return ret;
>>  	}
>>  
>> -	ret = request_threaded_irq(irq, NULL, opt3001_irq,
>> -			IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
>> -			"opt3001", iio);
>> -	if (ret) {
>> -		dev_err(dev, "failed to request IRQ #%d\n", irq);
>> -		return ret;
>> +	/* Make use of INT pin only if valid IRQ no. is given */
>> +	if (irq > 0) {
>> +		ret = request_threaded_irq(irq, NULL, opt3001_irq,
>> +				IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
>> +				"opt3001", iio);
>> +		if (ret) {
>> +			dev_err(dev, "failed to request IRQ #%d\n", irq);
>> +			return ret;
>> +		}
>> +		opt->use_irq = true;
>> +	} else {
>> +		dev_info(opt->dev, "enabling interrupt-less operation\n");
>>  	}
>>  
>>  	return 0;
>> @@ -754,7 +806,8 @@ static int opt3001_remove(struct i2c_client *client)
>>  	int ret;
>>  	u16 reg;
>>  
>> -	free_irq(client->irq, iio);
>> +	if (opt->use_irq)
>> +		free_irq(client->irq, iio);
>>  
>>  	ret = i2c_smbus_read_word_swapped(opt->client, OPT3001_CONFIGURATION);
>>  	if (ret < 0) {
>> -- 
>> 2.7.0
>>
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