[PATCH v5 9/9] iio: adc: mcp3911: add support to set PGA

Marcus Folkesson
2022-08-09T07:33:21Z

Add support for setting the Programmable Gain Amplifiers by adjust the
scale value.

Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
---
drivers/iio/adc/mcp3911.c | 107 +++++++++++++++++++++++++++++---------
1 file changed, 83 insertions(+), 24 deletions(-)

diff --git a/drivers/iio/adc/mcp3911.c b/drivers/iio/adc/mcp3911.c
index 61b516573207..ed8d0bb11fd6 100644
--- a/drivers/iio/adc/mcp3911.c
+++ b/drivers/iio/adc/mcp3911.c
@@ -28,6 +28,8 @@
#define MCP3911_REG_MOD 0x06
#define MCP3911_REG_PHASE 0x07
#define MCP3911_REG_GAIN 0x09
+#define MCP3911_GAIN_MASK(ch) (GENMASK(2, 0) << 3 * ch)
+#define MCP3911_GAIN_VAL(ch, val) ((val << 3 * ch) & MCP3911_GAIN_MASK(ch))

#define MCP3911_REG_STATUSCOM 0x0a
#define MCP3911_STATUSCOM_DRHIZ BIT(12)
@@ -58,8 +60,10 @@
#define MCP3911_REG_WRITE(reg, id) ((((reg) << 1) | ((id) << 5) | (0 << 0)) & 0xff)

#define MCP3911_NUM_CHANNELS 2
+#define MCP3911_NUM_SCALES 6

static const int mcp3911_osr_table[] = { 32, 64, 128, 256, 512, 1024, 2048, 4096 };
+static u32 mcp3911_scale_table[MCP3911_NUM_SCALES][2];

struct mcp3911 {
struct spi_device *spi;
@@ -68,6 +72,7 @@ struct mcp3911 {
struct clk *clki;
u32 dev_addr;
struct iio_trigger *trig;
+ u32 gain[MCP3911_NUM_CHANNELS];
struct {
u32 channels[MCP3911_NUM_CHANNELS];
s64 ts __aligned(8);
@@ -144,6 +149,11 @@ static int mcp3911_read_avail(struct iio_dev *indio_dev,
*vals = mcp3911_osr_table;
*length = ARRAY_SIZE(mcp3911_osr_table);
return IIO_AVAIL_LIST;
+ case IIO_CHAN_INFO_SCALE:
+ *type = IIO_VAL_INT_PLUS_NANO;
+ *vals = (int *)mcp3911_scale_table;
+ *length = ARRAY_SIZE(mcp3911_scale_table) * 2;
+ return IIO_AVAIL_LIST;
default:
return -EINVAL;
}
@@ -188,29 +198,9 @@ static int mcp3911_read_raw(struct iio_dev *indio_dev,
break;

case IIO_CHAN_INFO_SCALE:
- if (adc->vref) {
- ret = regulator_get_voltage(adc->vref);
- if (ret < 0) {
- dev_err(indio_dev->dev.parent,
- "failed to get vref voltage: %d\n",
- ret);
- goto out;
- }
-
- *val = ret / 1000;
- } else {
- *val = MCP3911_INT_VREF_MV;
- }
-
- /*
- * For 24bit Conversion
- * Raw = ((Voltage)/(Vref) * 2^23 * Gain * 1.5
- * Voltage = Raw * (Vref)/(2^23 * Gain * 1.5)
- */
-
- /* val2 = (2^23 * 1.5) */
- *val2 = 12582912;
- ret = IIO_VAL_FRACTIONAL;
+ *val = mcp3911_scale_table[ilog2(adc->gain[channel->channel])][0];
+ *val2 = mcp3911_scale_table[ilog2(adc->gain[channel->channel])][1];
+ ret = IIO_VAL_INT_PLUS_NANO;
break;
}

@@ -228,6 +218,18 @@ static int mcp3911_write_raw(struct iio_dev *indio_dev,

mutex_lock(&adc->lock);
switch (mask) {
+ case IIO_CHAN_INFO_SCALE:
+ for (int i = 0; i < MCP3911_NUM_SCALES; i++) {
+ if (val == mcp3911_scale_table[i][0] &&
+ val2 == mcp3911_scale_table[i][1]) {
+
+ adc->gain[channel->channel] = BIT(i);
+ ret = mcp3911_update(adc, MCP3911_REG_GAIN,
+ MCP3911_GAIN_MASK(channel->channel),
+ MCP3911_GAIN_VAL(channel->channel, i), 1);
+ }
+ }
+ break;
case IIO_CHAN_INFO_OFFSET:
if (val2 != 0) {
ret = -EINVAL;
@@ -263,6 +265,47 @@ static int mcp3911_write_raw(struct iio_dev *indio_dev,
return ret;
}

+static int mcp3911_calc_scale_table(struct mcp3911 *adc)
+{
+ u32 ref = MCP3911_INT_VREF_MV;
+ u32 div;
+ int ret;
+ int tmp0, tmp1;
+ s64 tmp2;
+
+ if (adc->vref) {
+ ret = regulator_get_voltage(adc->vref);
+ if (ret < 0) {
+ dev_err(&adc->spi->dev,
+ "failed to get vref voltage: %d\n",
+ ret);
+ return ret;
+ }
+
+ ref = ret / 1000;
+ }
+
+ /*
+ * For 24-bit Conversion
+ * Raw = ((Voltage)/(Vref) * 2^23 * Gain * 1.5
+ * Voltage = Raw * (Vref)/(2^23 * Gain * 1.5)
+ *
+ * ref = Reference voltage
+ * div = (2^23 * 1.5 * gain) = 12582912 * gain
+ */
+ for (int i = 0; i < MCP3911_NUM_SCALES; i++) {
+ div = 12582912 * BIT(i);
+ tmp2 = div_s64((s64)ref * 1000000000LL, div);
+ tmp1 = div;
+ tmp0 = (int)div_s64_rem(tmp2, 1000000000, &tmp1);
+
+ mcp3911_scale_table[i][0] = 0;
+ mcp3911_scale_table[i][1] = tmp1;
+ }
+
+ return 0;
+}
+
#define MCP3911_CHAN(idx) { \
.type = IIO_VOLTAGE, \
.indexed = 1, \
@@ -272,8 +315,10 @@ static int mcp3911_write_raw(struct iio_dev *indio_dev,
.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | \
BIT(IIO_CHAN_INFO_OFFSET) | \
BIT(IIO_CHAN_INFO_SCALE), \
- .info_mask_shared_by_type_available = \
+ .info_mask_shared_by_type_available = \
BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO), \
+ .info_mask_separate_available = \
+ BIT(IIO_CHAN_INFO_SCALE), \
.scan_type = { \
.sign = 's', \
.realbits = 24, \
@@ -501,6 +546,20 @@ static int mcp3911_probe(struct spi_device *spi)
if (ret)
return ret;

+ ret = mcp3911_calc_scale_table(adc);
+ if (ret)
+ return ret;
+
+ /* Set gain to 1 for all channels */
+ for (int i = 0; i < MCP3911_NUM_CHANNELS; i++) {
+ adc->gain[i] = 1;
+ ret = mcp3911_update(adc, MCP3911_REG_GAIN,
+ MCP3911_GAIN_MASK(i),
+ MCP3911_GAIN_VAL(i, 0), 1);
+ if (ret)
+ return ret;
+ }
+
indio_dev->name = spi_get_device_id(spi)->name;
indio_dev->modes = INDIO_DIRECT_MODE;
indio_dev->info = &mcp3911_info;
--
2.37.1