From 0eaecea6e4878abbf1d3e8de3e4eeabc856133d4 Mon Sep 17 00:00:00 2001 From: Mircea Caprioru Date: Tue, 25 Jun 2019 11:11:25 +0300 Subject: iio: adc: ad7124: Add buffered input support This patch adds the option to enable the buffered mode for positive and negative inputs. Each option can be enabled independently. In buffered mode, the input channel feeds into a high impedance input stage of the buffer amplifier. Therefore, the input can tolerate significant source impedances and is tailored for direct connection to external resistive type sensors such as strain gages or RTDs. Signed-off-by: Mircea Caprioru Signed-off-by: Jonathan Cameron --- drivers/iio/adc/ad7124.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) (limited to 'drivers/iio') diff --git a/drivers/iio/adc/ad7124.c b/drivers/iio/adc/ad7124.c index 810234db9c0d..ab52c5e9ecb1 100644 --- a/drivers/iio/adc/ad7124.c +++ b/drivers/iio/adc/ad7124.c @@ -61,6 +61,8 @@ #define AD7124_CONFIG_REF_SEL(x) FIELD_PREP(AD7124_CONFIG_REF_SEL_MSK, x) #define AD7124_CONFIG_PGA_MSK GENMASK(2, 0) #define AD7124_CONFIG_PGA(x) FIELD_PREP(AD7124_CONFIG_PGA_MSK, x) +#define AD7124_CONFIG_IN_BUFF_MSK GENMASK(7, 6) +#define AD7124_CONFIG_IN_BUFF(x) FIELD_PREP(AD7124_CONFIG_IN_BUFF_MSK, x) /* AD7124_FILTER_X */ #define AD7124_FILTER_FS_MSK GENMASK(10, 0) @@ -108,6 +110,8 @@ struct ad7124_chip_info { struct ad7124_channel_config { enum ad7124_ref_sel refsel; bool bipolar; + bool buf_positive; + bool buf_negative; unsigned int ain; unsigned int vref_mv; unsigned int pga_bits; @@ -473,6 +477,11 @@ static int ad7124_of_parse_channel_config(struct iio_dev *indio_dev, else st->channel_config[channel].refsel = tmp; + st->channel_config[channel].buf_positive = + of_property_read_bool(child, "adi,buffered-positive"); + st->channel_config[channel].buf_negative = + of_property_read_bool(child, "adi,buffered-negative"); + *chan = ad7124_channel_template; chan->address = channel; chan->scan_index = channel; @@ -492,7 +501,7 @@ err: static int ad7124_setup(struct ad7124_state *st) { unsigned int val, fclk, power_mode; - int i, ret; + int i, ret, tmp; fclk = clk_get_rate(st->mclk); if (!fclk) @@ -525,8 +534,12 @@ static int ad7124_setup(struct ad7124_state *st) if (ret < 0) return ret; + tmp = (st->channel_config[i].buf_positive << 1) + + st->channel_config[i].buf_negative; + val = AD7124_CONFIG_BIPOLAR(st->channel_config[i].bipolar) | - AD7124_CONFIG_REF_SEL(st->channel_config[i].refsel); + AD7124_CONFIG_REF_SEL(st->channel_config[i].refsel) | + AD7124_CONFIG_IN_BUFF(tmp); ret = ad_sd_write_reg(&st->sd, AD7124_CONFIG(i), 2, val); if (ret < 0) return ret; -- cgit v1.2.3-59-g8ed1b