[PATCH v4 08/14] iio: adc: ad7768: Add per-channel conversion delay

[Janani Sunil <janani.sunil@analog.com>]

Expose the per-channel synchronization phase offset through the IIO
conversion-delay attribute.

Derive the delay resolution from MCLK, power mode and decimation rate.
Validate the requested delay and program the corresponding phase
register when applying the active channel configuration.

Signed-off-by: Janani Sunil <janani.sunil@analog.com>
---
 drivers/iio/adc/ad7768.c | 143 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 143 insertions(+)

diff --git a/drivers/iio/adc/ad7768.c b/drivers/iio/adc/ad7768.c
index 289f3fa3142e..12370139d03f 100644
--- a/drivers/iio/adc/ad7768.c
+++ b/drivers/iio/adc/ad7768.c
@@ -24,6 +24,7 @@
 #include <linux/regulator/consumer.h>
 #include <linux/reset.h>
 #include <linux/spi/spi.h>
+#include <linux/time64.h>
 #include <linux/types.h>
 #include <linux/unaligned.h>
 #include <linux/units.h>
@@ -158,6 +159,12 @@ struct ad7768_freq_config {
 	unsigned int dec_rate;
 };
 
+struct ad7768_convdelay_params {
+	unsigned int shift;
+	unsigned int max_raw;
+	u64 step_ps;
+};
+
 struct ad7768_avail_freq {
 	unsigned int n_freqs;
 	unsigned int freqs[MAX_FREQ_PER_MODE];
@@ -187,6 +194,7 @@ struct ad7768_state {
 	unsigned int n_freqs;
 	int freqs[AD7768_MAX_FREQS];
 	unsigned int ch_freq[AD7768_MAX_CHANNEL];
+	u64 ch_convdelay_ps[AD7768_MAX_CHANNEL];
 	enum ad7768_filter_type ch_filter[AD7768_MAX_CHANNEL];
 	struct iio_backend *back;
 
@@ -250,6 +258,12 @@ static unsigned int ad7768_gain_reg(const struct ad7768_state *st,
 	return AD7768_REG_GAIN(st->chip_info->chan_map[ch]);
 }
 
+static unsigned int ad7768_phase_reg(const struct ad7768_state *st,
+				     unsigned int ch)
+{
+	return AD7768_REG_PHASE(st->chip_info->chan_map[ch]);
+}
+
 static u8 ad7768_precharge_buf1_mask(const struct ad7768_state *st, u16 val)
 {
 	return val & GENMASK(st->chip_info->prebuf_split - 1, 0);
@@ -615,6 +629,105 @@ static int ad7768_set_sampling_freq(struct iio_dev *indio_dev,
 	return 0;
 }
 
+static int ad7768_get_freq_cfg(struct ad7768_state *st, unsigned int freq,
+			       struct ad7768_freq_config *f_cfg)
+{
+	for (unsigned int i = 0;
+	     i < st->avail_freq[st->power_mode_idx].n_freqs; i++) {
+		*f_cfg = st->avail_freq[st->power_mode_idx].freq_cfg[i];
+		if (freq == f_cfg->freq_hz)
+			return 0;
+	}
+
+	return -EINVAL;
+}
+
+static int ad7768_get_convdelay_params(struct ad7768_state *st, unsigned int ch,
+				       struct ad7768_convdelay_params *params)
+{
+	struct ad7768_freq_config f_cfg;
+	unsigned int dec_rate;
+	unsigned int mclk_div;
+	unsigned int mult;
+	u64 mclk;
+	int ret;
+
+	ret = ad7768_get_freq_cfg(st, st->ch_freq[ch], &f_cfg);
+	if (ret)
+		return ret;
+
+	dec_rate = ad7768_dec_rate[f_cfg.dec_rate];
+	switch (dec_rate) {
+	case 32:
+		params->shift = 3;
+		params->max_raw = 31;
+		mult = 1;
+		break;
+	case 64:
+		params->shift = 2;
+		params->max_raw = 63;
+		mult = 1;
+		break;
+	case 128:
+		params->shift = 1;
+		params->max_raw = 127;
+		mult = 1;
+		break;
+	case 256:
+		params->shift = 0;
+		params->max_raw = 255;
+		mult = 1;
+		break;
+	case 512:
+		params->shift = 0;
+		params->max_raw = 255;
+		mult = 2;
+		break;
+	case 1024:
+		params->shift = 0;
+		params->max_raw = 255;
+		mult = 4;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	mclk = clk_get_rate(st->mclk);
+	if (!mclk)
+		return -EINVAL;
+
+	mclk_div = ad7768_power_modes[st->power_mode_idx].mclk_div;
+	params->step_ps = DIV_ROUND_CLOSEST_ULL((u64)mult * PSEC_PER_SEC *
+						mclk_div, mclk);
+
+	return 0;
+}
+
+static int ad7768_set_channel_convdelay(struct ad7768_state *st,
+					unsigned int ch)
+{
+	u64 delay_ps = st->ch_convdelay_ps[ch];
+	struct ad7768_convdelay_params params;
+	u64 max_delay_ps;
+	u64 raw;
+	int ret;
+
+	ret = ad7768_get_convdelay_params(st, ch, &params);
+	if (ret)
+		return ret;
+
+	max_delay_ps = (u64)params.max_raw * params.step_ps;
+	if (delay_ps > max_delay_ps)
+		return -EINVAL;
+
+	raw = DIV_ROUND_CLOSEST_ULL(delay_ps, params.step_ps);
+	if (raw > params.max_raw)
+		return -EINVAL;
+
+	return regmap_write(st->regmap, ad7768_phase_reg(st, ch),
+			    raw << params.shift);
+}
+
 static void ad7768_filter_wait(const unsigned int *mode_freq,
 			       const enum ad7768_filter_type *mode_filter,
 			       const bool *mode_used)
@@ -738,6 +851,16 @@ static int ad7768_apply_channel_modes(struct iio_dev *indio_dev,
 		max_freq = max(max_freq, mode_freq[mode]);
 	}
 
+	for_each_set_bit(c, scan_mask, st->chip_info->num_channels) {
+		ret = ad7768_set_channel_convdelay(st, c);
+		if (ret == -EINVAL)
+			return dev_err_probe(regmap_get_device(st->regmap), ret,
+					     "Invalid conversion delay for channel %u\n",
+					     c);
+		if (ret)
+			return ret;
+	}
+
 	ret = ad7768_set_clk_divs(st, max_freq);
 	if (ret)
 		return ret;
@@ -788,6 +911,13 @@ static int ad7768_read_raw(struct iio_dev *indio_dev,
 
 		*val = calib;
 		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_CONVDELAY: {
+		guard(mutex)(&st->lock);
+		iio_val_s64_decompose(st->ch_convdelay_ps[chan->channel],
+				      val, val2);
+
+		return IIO_VAL_DECIMAL64_PICO;
+	}
 	default:
 		return -EINVAL;
 	}
@@ -801,6 +931,8 @@ static int ad7768_write_raw_get_fmt(struct iio_dev *indio_dev,
 	case IIO_CHAN_INFO_CALIBBIAS:
 	case IIO_CHAN_INFO_CALIBSCALE:
 		return IIO_VAL_INT;
+	case IIO_CHAN_INFO_CONVDELAY:
+		return IIO_VAL_DECIMAL64_PICO;
 	default:
 		return -EINVAL;
 	}
@@ -812,6 +944,7 @@ static int ad7768_write_raw(struct iio_dev *indio_dev,
 {
 	struct ad7768_state *st = iio_priv(indio_dev);
 	unsigned int base_reg;
+	s64 delay_ps;
 	int ret;
 
 	IIO_DEV_ACQUIRE_DIRECT_MODE(indio_dev, claim);
@@ -838,6 +971,15 @@ static int ad7768_write_raw(struct iio_dev *indio_dev,
 
 		base_reg = ad7768_get_calib_reg_base(st, chan, true);
 		return ad7768_write_calib_value(st, base_reg, val);
+	case IIO_CHAN_INFO_CONVDELAY: {
+		delay_ps = iio_val_s64_compose(val, val2);
+		if (delay_ps < 0)
+			return -EINVAL;
+
+		guard(mutex)(&st->lock);
+		st->ch_convdelay_ps[chan->channel] = delay_ps;
+		return 0;
+	}
 	default:
 		return -EINVAL;
 	}
@@ -1133,6 +1275,7 @@ static int ad7768_parse_config(struct iio_dev *indio_dev,
 			.type = IIO_VOLTAGE,
 			.info_mask_separate = BIT(IIO_CHAN_INFO_CALIBBIAS) |
 					      BIT(IIO_CHAN_INFO_CALIBSCALE) |
+					      BIT(IIO_CHAN_INFO_CONVDELAY) |
 					      BIT(IIO_CHAN_INFO_SAMP_FREQ),
 			.info_mask_separate_available =
 				BIT(IIO_CHAN_INFO_SAMP_FREQ),

-- 
2.43.0