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iio: mxs-lradc: compute temperature from channel 8 and 9 

The mxs LRADC is able to read an internal die temperature sensor. The
temperature has to be calculated from the value read on channel 8 and channel 9.
To be able to expose the result to hwmon, implement iio channel 8 as
(channel 9 - channel 8). Then, implement IIO_CHAN_INFO_SCALE and
IIO_CHAN_INFO_OFFSET so that it can be processed by hwmon through the in kernel
provider/consumer mechanism.

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
This commit is contained in:
Alexandre Belloni 2013-12-06 19:31:00 +00:00 committed by Jonathan Cameron
parent 098d3beccf
commit c8231a9af8
1 changed files with 78 additions and 13 deletions
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91
drivers/staging/iio/adc/mxs-lradc.c
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@ -759,20 +759,11 @@ static void mxs_lradc_handle_touch(struct mxs_lradc *lradc)
/*
* Raw I/O operations
*/
static int mxs_lradc_read_raw(struct iio_dev *iio_dev,
const struct iio_chan_spec *chan,
int *val, int *val2, long m)
static int mxs_lradc_read_single(struct iio_dev *iio_dev, int chan, int *val)
{
struct mxs_lradc *lradc = iio_priv(iio_dev);
int ret;
if (m != IIO_CHAN_INFO_RAW)
return -EINVAL;
/* Check for invalid channel */
if (chan->channel > LRADC_MAX_TOTAL_CHANS)
return -EINVAL;
/*
* See if there is no buffered operation in progess. If there is, simply
* bail out. This can be improved to support both buffered and raw IO at
@ -797,7 +788,7 @@ static int mxs_lradc_read_raw(struct iio_dev *iio_dev,
/* Clean the slot's previous content, then set new one. */
mxs_lradc_reg_clear(lradc, LRADC_CTRL4_LRADCSELECT_MASK(0), LRADC_CTRL4);
mxs_lradc_reg_set(lradc, chan->channel, LRADC_CTRL4);
mxs_lradc_reg_set(lradc, chan, LRADC_CTRL4);
mxs_lradc_reg_wrt(lradc, 0, LRADC_CH(0));
@ -824,6 +815,71 @@ static int mxs_lradc_read_raw(struct iio_dev *iio_dev,
return ret;
}
static int mxs_lradc_read_temp(struct iio_dev *iio_dev, int *val)
{
int ret, min, max;
ret = mxs_lradc_read_single(iio_dev, 8, &min);
if (ret != IIO_VAL_INT)
return ret;
ret = mxs_lradc_read_single(iio_dev, 9, &max);
if (ret != IIO_VAL_INT)
return ret;
*val = max - min;
return IIO_VAL_INT;
}
static int mxs_lradc_read_raw(struct iio_dev *iio_dev,
const struct iio_chan_spec *chan,
int *val, int *val2, long m)
{
/* Check for invalid channel */
if (chan->channel > LRADC_MAX_TOTAL_CHANS)
return -EINVAL;
switch (m) {
case IIO_CHAN_INFO_RAW:
if (chan->type == IIO_TEMP)
return mxs_lradc_read_temp(iio_dev, val);
return mxs_lradc_read_single(iio_dev, chan->channel, val);
case IIO_CHAN_INFO_SCALE:
if (chan->type == IIO_TEMP) {
/* From the datasheet, we have to multiply by 1.012 and
* divide by 4
*/
*val = 0;
*val2 = 253000;
return IIO_VAL_INT_PLUS_MICRO;
}
return -EINVAL;
case IIO_CHAN_INFO_OFFSET:
if (chan->type == IIO_TEMP) {
/* The calculated value from the ADC is in Kelvin, we
* want Celsius for hwmon so the offset is
* -272.15 * scale
*/
*val = -1075;
*val2 = 691699;
return IIO_VAL_INT_PLUS_MICRO;
}
return -EINVAL;
default:
break;
}
return -EINVAL;
}
static const struct iio_info mxs_lradc_iio_info = {
.driver_module = THIS_MODULE,
.read_raw = mxs_lradc_read_raw,
@ -1151,8 +1207,17 @@ static const struct iio_chan_spec mxs_lradc_chan_spec[] = {
MXS_ADC_CHAN(5, IIO_VOLTAGE),
MXS_ADC_CHAN(6, IIO_VOLTAGE),
MXS_ADC_CHAN(7, IIO_VOLTAGE), /* VBATT */
MXS_ADC_CHAN(8, IIO_TEMP), /* Temp sense 0 */
MXS_ADC_CHAN(9, IIO_TEMP), /* Temp sense 1 */
/* Combined Temperature sensors */
{
.type = IIO_TEMP,
.indexed = 1,
.scan_index = 8,
.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
BIT(IIO_CHAN_INFO_OFFSET) |
BIT(IIO_CHAN_INFO_SCALE),
.channel = 8,
.scan_type = {.sign = 'u', .realbits = 18, .storagebits = 32,},
},
MXS_ADC_CHAN(10, IIO_VOLTAGE), /* VDDIO */
MXS_ADC_CHAN(11, IIO_VOLTAGE), /* VTH */
MXS_ADC_CHAN(12, IIO_VOLTAGE), /* VDDA */