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Date: Mon, 1 Jul 2013 19:16:58 +0200
From: Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To: Jonathan Cameron <jic23@....ac.uk>
Cc: Maxime Ripard <maxime.ripard@...e-electrons.com>, jimwall@...om,
brian@...stalfontz.com,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
linux-iio@...r.kernel.org, devel@...verdev.osuosl.org,
linux-kernel@...r.kernel.org, Lars-Peter Clausen <lars@...afoo.de>,
Alexandre Belloni <alexandre.belloni@...e-electrons.com>
Subject: [RFC] 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@...e-electrons.com>
---
drivers/staging/iio/adc/mxs-lradc.c | 99 ++++++++++++++++++++++++++++++-------
1 file changed, 82 insertions(+), 17 deletions(-)
diff --git a/drivers/staging/iio/adc/mxs-lradc.c b/drivers/staging/iio/adc/mxs-lradc.c
index 163c638..df1d81e 100644
--- a/drivers/staging/iio/adc/mxs-lradc.c
+++ b/drivers/staging/iio/adc/mxs-lradc.c
@@ -225,26 +225,14 @@ struct mxs_lradc {
#define LRADC_CTRL4_LRADCSELECT_MASK(n) (0xf << ((n) * 4))
#define LRADC_CTRL4_LRADCSELECT_OFFSET(n) ((n) * 4)
-/*
- * 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;
unsigned long mask;
- if (m != IIO_CHAN_INFO_RAW)
- return -EINVAL;
-
- /* Check for invalid channel */
- if (chan->channel > LRADC_MAX_TOTAL_CHANS)
- return -EINVAL;
-
/* Validate the channel if it doesn't intersect with reserved chans. */
- bitmap_set(&mask, chan->channel, 1);
+ bitmap_set(&mask, chan, 1);
ret = iio_validate_scan_mask_onehot(iio_dev, &mask);
if (ret)
return -EINVAL;
@@ -273,7 +261,7 @@ static int mxs_lradc_read_raw(struct iio_dev *iio_dev,
/* Clean the slot's previous content, then set new one. */
writel(LRADC_CTRL4_LRADCSELECT_MASK(0),
lradc->base + LRADC_CTRL4 + STMP_OFFSET_REG_CLR);
- writel(chan->channel, lradc->base + LRADC_CTRL4 + STMP_OFFSET_REG_SET);
+ writel(chan, lradc->base + LRADC_CTRL4 + STMP_OFFSET_REG_SET);
writel(0, lradc->base + LRADC_CH(0));
@@ -302,6 +290,74 @@ err:
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;
+}
+
+/*
+ * 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)
+{
+ /* 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,
@@ -836,8 +892,17 @@ 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 */
--
1.8.1.2
--
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