[PATCH v5 04/12] iio: dac: ad5686: fix powerdown control on dual-channel devices

[Rodrigo Alencar via B4 Relay]

From: Rodrigo Alencar <rodrigo.alencar@xxxxxxxxxx>

Fix powerdown control by using a proper bit shift for the powerdown mask
values. During initialization, powerdown bits are initialized so that
unused bits are set to 1 and the correct bit shift is used. Dual-channel
devices use one-hot encoding in the address and that reflects on the
position of the powerdown bits, which are not channel-index based
for that case. Quad-channel devices also use one-hot encoding for the
channel address but the result of log2(address) coincides with the channel
index value. The issue was introduced when first adding support for
dual-channel devices, which overlooked powerdown control differences.

Fixes: 7dc8faeab3e3 ("iio: dac: ad5686: add support for AD5338R")
Signed-off-by: Rodrigo Alencar <rodrigo.alencar@xxxxxxxxxx>
---
 drivers/iio/dac/ad5686.c | 40 ++++++++++++++++++++++++++++++----------
 1 file changed, 30 insertions(+), 10 deletions(-)

diff --git a/drivers/iio/dac/ad5686.c b/drivers/iio/dac/ad5686.c
index 69358dd66cbc..c607251b82a0 100644
--- a/drivers/iio/dac/ad5686.c
+++ b/drivers/iio/dac/ad5686.c
@@ -25,24 +25,35 @@ static const char * const ad5686_powerdown_modes[] = {
 	"three_state"
 };
 
+static inline unsigned int ad5686_pd_mask_shift(const struct iio_chan_spec *chan)
+{
+	if (chan->channel == chan->address)
+		return chan->channel * 2;
+
+	/* one-hot encoding is used in dual/quad channel devices */
+	return __ffs(chan->address) * 2;
+}
+
 static int ad5686_get_powerdown_mode(struct iio_dev *indio_dev,
 				     const struct iio_chan_spec *chan)
 {
+	unsigned int shift = ad5686_pd_mask_shift(chan);
 	struct ad5686_state *st = iio_priv(indio_dev);
 
-	return ((st->pwr_down_mode >> (chan->channel * 2)) & 0x3) - 1;
+	return ((st->pwr_down_mode >> shift) & 0x3) - 1;
 }
 
 static int ad5686_set_powerdown_mode(struct iio_dev *indio_dev,
 				     const struct iio_chan_spec *chan,
 				     unsigned int mode)
 {
+	unsigned int shift = ad5686_pd_mask_shift(chan);
 	struct ad5686_state *st = iio_priv(indio_dev);
 
 	guard(mutex)(&st->lock);
 
-	st->pwr_down_mode &= ~(0x3 << (chan->channel * 2));
-	st->pwr_down_mode |= ((mode + 1) << (chan->channel * 2));
+	st->pwr_down_mode &= ~(0x3 << shift);
+	st->pwr_down_mode |= (mode + 1) << shift;
 
 	return 0;
 }
@@ -57,10 +68,10 @@ static const struct iio_enum ad5686_powerdown_mode_enum = {
 static ssize_t ad5686_read_dac_powerdown(struct iio_dev *indio_dev,
 		uintptr_t private, const struct iio_chan_spec *chan, char *buf)
 {
+	unsigned int shift = ad5686_pd_mask_shift(chan);
 	struct ad5686_state *st = iio_priv(indio_dev);
 
-	return sysfs_emit(buf, "%d\n", !!(st->pwr_down_mask &
-				       (0x3 << (chan->channel * 2))));
+	return sysfs_emit(buf, "%d\n", !!(st->pwr_down_mask & (0x3 << shift)));
 }
 
 static ssize_t ad5686_write_dac_powerdown(struct iio_dev *indio_dev,
@@ -82,9 +93,9 @@ static ssize_t ad5686_write_dac_powerdown(struct iio_dev *indio_dev,
 	guard(mutex)(&st->lock);
 
 	if (readin)
-		st->pwr_down_mask |= (0x3 << (chan->channel * 2));
+		st->pwr_down_mask |= 0x3 << ad5686_pd_mask_shift(chan);
 	else
-		st->pwr_down_mask &= ~(0x3 << (chan->channel * 2));
+		st->pwr_down_mask &= ~(0x3 << ad5686_pd_mask_shift(chan));
 
 	switch (st->chip_info->regmap_type) {
 	case AD5310_REGMAP:
@@ -464,7 +475,7 @@ int ad5686_probe(struct device *dev,
 {
 	struct ad5686_state *st;
 	struct iio_dev *indio_dev;
-	unsigned int val, ref_bit_msk;
+	unsigned int val, ref_bit_msk, shift;
 	bool has_external_vref;
 	u8 cmd;
 	int ret, i;
@@ -488,9 +499,18 @@ int ad5686_probe(struct device *dev,
 	has_external_vref = ret != -ENODEV;
 	st->vref_mv = has_external_vref ? ret / 1000 : st->chip_info->int_vref_mv;
 
+	/* Initialize masks to all ones provided the max shift (last channel) */
+	shift = ad5686_pd_mask_shift(&st->chip_info->channels[st->chip_info->num_channels - 1]);
+	st->pwr_down_mask = GENMASK(shift + 1, 0);
+	st->pwr_down_mode = GENMASK(shift + 1, 0);
+
 	/* Set all the power down mode for all channels to 1K pulldown */
-	for (i = 0; i < st->chip_info->num_channels; i++)
-		st->pwr_down_mode |= (0x01 << (i * 2));
+	for (i = 0; i < st->chip_info->num_channels; i++) {
+		shift = ad5686_pd_mask_shift(&st->chip_info->channels[i]);
+		st->pwr_down_mask &= ~(0x3 << shift); /* powered up state */
+		st->pwr_down_mode &= ~(0x3 << shift);
+		st->pwr_down_mode |= 0x01 << shift;
+	}
 
 	indio_dev->name = name;
 	indio_dev->info = &ad5686_info;

-- 
2.43.0