Re: [PATCH v6] iio: adc: add new lp8788 adc driver

[Jonathan Cameron <jic23@kernel.org>]

On 09/18/2012 09:18 PM, Jonathan Cameron wrote:
> On 09/18/2012 09:19 AM, Lars-Peter Clausen wrote:
>> On 09/17/2012 11:35 AM, Kim, Milo wrote:
>>>  TI LP8788 PMU provides regulators, battery charger, ADC,
>>>  RTC, backlight driver and current sinks.
>>>
>>>  This patch enables the LP8788 ADC functions.
>>>
>>>  The LP8788 ADC has several ADC input selection and supports 12bit resolution.
>>>  Internal operation of getting ADC is access to registers of LP8788.
>>>  The LP8788 ADC uses exported functions for accessing these registers.
>>>  (exported by LP8788 MFD device driver)
>>>
>>>  This driver supports IIO_CHAN_INFO_RAW and SCALE.
>>>  So the IIO consumer can calculate the value with raw and scale.
>>>  The unit of scale is micro.
>>>
>>>  (ADC Input Selection)
>>>
>>>  Voltage: battery voltage (MAX 5.0, 5.5 and 6.0V)
>>>           charger input voltage
>>>           four general ADC inputs
>>>           coin cell voltage
>>>  Current: battery charging current
>>>  Temperature: IC temperature
>>>
>>>  (The IIO map for the IIO consumer)
>>>
>>>  The ADC input is configurable in the platform side.
>>>  Even though this platform data is not defined,
>>>  the default IIO map is created for supporting the power supply driver.
>>>  The battery voltage and temperature are used inside this driver.
>>>
>>>  (History)
>>>
>>>  Patch v6.
>>>  (a) Fix scale value for each ADC input selection
>>>  Voltage and current type are mili unit and temperature is degree.
>>>  To calculate the IC temperature,
>>>  temp = raw * scaleint + (raw * scalepart)/ 1000000, scaleint is always 0.
>>>       = raw * 0.061050, raw: 0 ~ 4095
>>>  Then range of IC temperature(ADC result) is 0 ~ 250'C
>>>
>>>  (b) Reorganization of the IIO channel Spec
>>>  Remove address, scan_type and scan_index and rollback the datasheet name.
>>>  The reason why 'address' field is unnecessary is no relation with each channel.
>>>  Moreover, to get the raw ADC value, the address info is not only one register
>>>  but also several registers.
>>>  Therefore specific function(lp8788_get_adc_result) is called rather than
>>>  using one 'address' field.
>>>
>>>  (c) Fix coding style
>>>  Remove duplicated checking routine while unregistering the IIO map.
>>>  Fix code for space and parenthesis.
>>>
>>>  Patch v5.
>>>  Fix default consumer name as 'lp8788-charger'.
>>>  Add mutex for ADC read operation.
>>>  Reorganization on lp8788_adc_read_raw().
>>>
>>>  Patch v4.
>>>  Fix adc_raw function: support RAW and SCALE channel info.
>>>  Change LP8788 ADC platform data - iio map.
>>>  Enables the default IIO map.
>>>
>>>  Patch v3.
>>>  Fix wrong size of allocating iio private data.
>>>  Fix coding styles.
>>>
>>>  Patch v2.
>>>  Support RAW and SCALE interface for IIO consumer.
>>>  Clean up the iio channel spec macro.
>>>
>>> Signed-off-by: Milo(Woogyom) Kim <milo.kim@ti.com>
>>
>> Looks good to me,
>>
>> Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
> I've added this to my local tree but not pushed out just
> yet on basis you might want to change the behaviour Lars
> has pointed out...
> 
> I don't here it'll go as is in a day or so.

Added to togreg branch of iio.git
> 
> Jonathan
>>
>> One comment though, not sure if it is critical or not.
>>
>>> +static int lp8788_get_adc_result(struct lp8788_adc *adc, enum lp8788_adc_id id,
>>> +				int *val)
>>> +{
>>> +	unsigned int msb;
>>> +	unsigned int lsb;
>>> +	unsigned int result;
>>> +	u8 data;
>>> +	u8 rawdata[2];
>>> +	int size = ARRAY_SIZE(rawdata);
>>> +	int retry = 5;
>>> +	int ret;
>>> +
>>> +	data = (id << 1) | ADC_CONV_START;
>>> +	ret = lp8788_write_byte(adc->lp, LP8788_ADC_CONF, data);
>>> +	if (ret)
>>> +		goto err_io;
>>> +
>>> +	/* retry until adc conversion is done */
>>> +	data = 0;
>>> +	while (retry--) {
>>> +		usleep_range(100, 200);
>>> +
>>> +		ret = lp8788_read_byte(adc->lp, LP8788_ADC_DONE, &data);
>>> +		if (ret)
>>> +			goto err_io;
>>> +
>>> +		/* conversion done */
>>> +		if (data)
>>> +			break;
>>
>> Could as well go into the while header like this:
>>     while (!data && retry--)
>>
>>> +	}
>>> +
>>
>> You still sample the data, even if there was a timeout and ADC_DONE is not set.
>>
>>> +	ret = lp8788_read_multi_bytes(adc->lp, LP8788_ADC_RAW, rawdata, size);
>>> +	if (ret)
>>> +		goto err_io;
>>> +
>>> +	msb = (rawdata[0] << 4) & 0x00000ff0;
>>> +	lsb = (rawdata[1] >> 4) & 0x0000000f;
>>> +	result = msb | lsb;
>>> +	*val = result;
>>> +
>>> +	return 0;
>>> +
>>> +err_io:
>>> +	return ret;
>>> +}
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