Re: [PATCH 3/5] iio: adc: sunxi-gpadc-iio: enable iio_buffers

Quentin Schulz
2016-07-20T08:57:45Z

On 20/07/2016 10:38, Peter Meerwald-Stadler wrote:
>
>> This enables the use of buffers on ADC channels of sunxi-gpadc-iio driver.
>> It also prepares the code which will be used by the touchscreen driver
>> named sunxi-gpadc-ts.
>>
>> The GPADC on Allwinner SoCs (A10, A13 and A31) has a 12 bits register for
>> conversion's data. The GPADC uses the same ADC channels for the ADC and the
>> touchscreen therefore exposes these channels to the sunxi-gpadc-ts iio
>> consumer which will be in charge of reading data from these channels for
>> the input framework.
>>
>> The temperature can only be read when in touchscreen mode. This means if
>> the buffers are being used for the ADC, the temperature sensor cannot be
>> read.
>>
>> When a FIFO_DATA_PENDING irq occurs, its handler will read the entire FIFO
>> and fill a buffer before sending it to the consumers which registered in
>> IIO for the ADC channels.
>>
>> When a consumer starts buffering ADC channels,
>> sunxi_gpadc_buffer_postenable is called and will enable FIFO_DATA_PENDING
>> irq and select the mode in which the GPADC should run (ADC or touchscreen)
>> depending on a property of the DT ("allwinner,ts-attached").
>> When the consumer stops buffering, it disables the same irq.
>
> comments below
>
[...]
>> @@ -101,19 +104,43 @@ struct sunxi_gpadc_dev {
>> unsigned int fifo_data_irq;
>> unsigned int temp_data_irq;
>> unsigned int flags;
>> + struct iio_dev *indio_dev;
>> + struct sunxi_gpadc_buffer buffer;
>> + bool ts_attached;
>> + bool buffered;
>
> why add buffered, duplicate state and not query iio_buffer_enabled()?
>
>> };
>>
>> -#define SUNXI_GPADC_ADC_CHANNEL(_channel, _name) { \
>> +#define SUNXI_GPADC_ADC_CHANNEL(_channel, _name, _index) { \
>> .type = IIO_VOLTAGE, \
>> .indexed = 1, \
>> .channel = _channel, \
>> .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
>> .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
>> .datasheet_name = _name, \
>> + .scan_index = _index, \
>> + .scan_type = { \
>> + .sign = 'u', \
>> + .realbits = 12, \
>> + .storagebits = 16, \
>> + .shift = 0, \
>
> shift not strictly needed
>

ACK.

[...]
>> static int sunxi_gpadc_read_raw(struct iio_dev *indio_dev,
>> @@ -219,15 +253,22 @@ static int sunxi_gpadc_read_raw(struct iio_dev *indio_dev,
>> int *val, int *val2, long mask)
>> {
>> int ret;
>> + struct sunxi_gpadc_dev *info = iio_priv(indio_dev);
>>
>> switch (mask) {
>> case IIO_CHAN_INFO_PROCESSED:
>> + if (info->buffered && !info->ts_attached)
>> + return -EBUSY;
>
> there would be iio_device_claim_direct_mode()
>

OK, iio_device_claim_direct_mode() and iio_device_release_direct_mode()
are new functions which are not yet in the Linux Cross Reference
(http://lxr.free-electrons.com/), I didn't know they existed. I'll use
that, iio_buffer_enabled() when needed and get rid of the buffered
boolean variable.

[...]
Thanks.

Quentin