[RFC PATCH 5/6] iio: light: ROHM BU27034 Ambient Light Sensor

From: Matti Vaittinen
Date: Wed Feb 22 2023 - 11:16:16 EST

ROHM BU27034 is an ambient light sesnor with 3 channels and 3 photo diodes
capable of detecting a very wide range of illuminance. Typical application
is adjusting LCD and backlight power of TVs and mobile phones.

Add initial support for the ROHM BU27034 ambient light sensor.

NOTE:
- Driver exposes 4 channels. One IIO_LIGHT channel providing the
calculated lux values based on measured data from diodes #0 and
#1. Additionally 3 IIO_INTENSITY channels are emitting the raw
register data from all diodes for more intense user-space
computations.
- Sensor has adjustible GAIN values ranging from 1x to 4096x.
- Sensor has adjustible measurement times 5, 55, 100, 200 and
400 mS. Driver does not support 5 mS which has special
limitations.
- Driver exposes standard 'scale' adjustment which is
implemented by:
1) Trying to adjust only the GAIN
2) If GAIN adjustment only can't provide requested
scale, adjusting both the time and the gain is
attempted.
- Driver exposes writable INT_TIME property which can be used
for adjusting the measurement time. Time adjustment will also
cause the driver to adjust the GAIN so that the overall scale
is not changed.
- Runtime PM is not implemented.
- Driver starts the measurement on the background when it is
probed. This improves the respnse time to read-requests
compared to starting the read only when data is requested.
When the most accurate 400 mS measurement time is used, data reads
would last quite long if measurement was started only on
demand. This, however, is not appealing for users who would
prefere power saving over measurement response time.

Signed-off-by: Matti Vaittinen <mazziesaccount@xxxxxxxxx>

---
---
drivers/iio/light/Kconfig | 13 +
drivers/iio/light/Makefile | 1 +
drivers/iio/light/rohm-bu27034.c | 1212 ++++++++++++++++++++++++++++++
3 files changed, 1226 insertions(+)
create mode 100644 drivers/iio/light/rohm-bu27034.c

diff --git a/drivers/iio/light/Kconfig b/drivers/iio/light/Kconfig
index 671d84f98c56..594228bd1f7f 100644
--- a/drivers/iio/light/Kconfig
+++ b/drivers/iio/light/Kconfig
@@ -292,6 +292,19 @@ config JSA1212
To compile this driver as a module, choose M here:
the module will be called jsa1212.

+config ROHM_BU27034
+ tristate "ROHM BU27034 ambient light sensor"
+ depends on I2C
+ select REGMAP_I2C
+ select IIO_GTS_HELPER
+ help
+ Enable support for the ROHM BU27034 ambient light sensor.
+ ROHM BU27034 is an ambient light sesnor with 3 channels and
+ 3 photo diodes capable of detecting a very wide range of
+ illuminance.
+ Typical application is adjusting LCD and backlight power
+ of TVs and mobile phones.
+
config RPR0521
tristate "ROHM RPR0521 ALS and proximity sensor driver"
depends on I2C
diff --git a/drivers/iio/light/Makefile b/drivers/iio/light/Makefile
index f4705fac7a96..d34a0f7bf6ce 100644
--- a/drivers/iio/light/Makefile
+++ b/drivers/iio/light/Makefile
@@ -39,6 +39,7 @@ obj-$(CONFIG_MAX44009) += max44009.o
obj-$(CONFIG_NOA1305) += noa1305.o
obj-$(CONFIG_OPT3001) += opt3001.o
obj-$(CONFIG_PA12203001) += pa12203001.o
+obj-$(CONFIG_ROHM_BU27034) += rohm-bu27034.o
obj-$(CONFIG_RPR0521) += rpr0521.o
obj-$(CONFIG_SENSORS_TSL2563) += tsl2563.o
obj-$(CONFIG_SI1133) += si1133.o
diff --git a/drivers/iio/light/rohm-bu27034.c b/drivers/iio/light/rohm-bu27034.c
new file mode 100644
index 000000000000..235be7dee6e0
--- /dev/null
+++ b/drivers/iio/light/rohm-bu27034.c
@@ -0,0 +1,1212 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * BU27034 ROHM Ambient Light Sensor
+ *
+ * Copyright (c) 2023, ROHM Semiconductor.
+ * https://fscdn.rohm.com/en/products/databook/datasheet/ic/sensor/light/bu27034nuc-e.pdf
+ */
+
+#include <linux/bits.h>
+#include <linux/device.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+#include <linux/regulator/consumer.h>
+#include <linux/units.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+
+#include "gain-time-scale-helper.h"
+
+#define BU27034_REG_SYSTEM_CONTROL 0x40
+#define BU27034_MASK_SW_RESET BIT(7)
+#define BU27034_MASK_PART_ID GENMASK(5, 0)
+#define BU27034_ID 0x19
+#define BU27034_REG_MODE_CONTROL1 0x41
+#define BU27034_MASK_MEAS_MODE GENMASK(2, 0)
+
+#define BU27034_REG_MODE_CONTROL2 0x42
+#define BU27034_MASK_D01_GAIN GENMASK(7, 3)
+#define BU27034_SHIFT_D01_GAIN 3
+#define BU27034_MASK_D2_GAIN_HI GENMASK(7, 6)
+#define BU27034_MASK_D2_GAIN_LO GENMASK(2, 0)
+#define BU27034_SHIFT_D2_GAIN 3
+
+#define BU27034_REG_MODE_CONTROL3 0x43
+#define BU27034_REG_MODE_CONTROL4 0x44
+#define BU27034_MASK_MEAS_EN BIT(0)
+#define BU27034_MASK_VALID BIT(7)
+#define BU27034_REG_DATA0_LO 0x50
+#define BU27034_REG_DATA1_LO 0x52
+#define BU27034_REG_DATA2_LO 0x54
+#define BU27034_REG_DATA2_HI 0x55
+#define BU27034_REG_MANUFACTURER_ID 0x92
+#define BU27034_REG_MAX BU27034_REG_MANUFACTURER_ID
+
+enum {
+ BU27034_CHAN_ALS,
+ BU27034_CHAN_DATA0,
+ BU27034_CHAN_DATA1,
+ BU27034_CHAN_DATA2,
+ BU27034_NUM_CHANS
+};
+
+/*
+ * Available scales with gain 1x - 4096x, timings 55, 100, 200, 400 mS
+ * Time impacts to gain: 1x, 2x, 4x, 8x.
+ *
+ * => Max total gain is HWGAIN * gain by integration time (8 * 4096) = 32768
+ *
+ * Using NANO precision for scale we must use scale 64x corresponding gain 1x
+ * to avoid precision loss. (32x would result scale 976 562.5(nanos).
+ */
+#define BU27034_SCALE_1X 64
+
+#define BU27034_GSEL_1X 0x00
+#define BU27034_GSEL_4X 0x08
+#define BU27034_GSEL_16X 0x0a
+#define BU27034_GSEL_32X 0x0b
+#define BU27034_GSEL_64X 0x0c
+#define BU27034_GSEL_256X 0x18
+#define BU27034_GSEL_512X 0x19
+#define BU27034_GSEL_1024X 0x1a
+#define BU27034_GSEL_2048X 0x1b
+#define BU27034_GSEL_4096X 0x1c
+
+/* Available gain settings */
+static const struct iio_gain_sel_pair bu27034_gains[] = {
+ GAIN_SCALE_GAIN(1, BU27034_GSEL_1X),
+ GAIN_SCALE_GAIN(4, BU27034_GSEL_4X),
+ GAIN_SCALE_GAIN(16, BU27034_GSEL_16X),
+ GAIN_SCALE_GAIN(32, BU27034_GSEL_32X),
+ GAIN_SCALE_GAIN(64, BU27034_GSEL_64X),
+ GAIN_SCALE_GAIN(256, BU27034_GSEL_256X),
+ GAIN_SCALE_GAIN(512, BU27034_GSEL_512X),
+ GAIN_SCALE_GAIN(1024, BU27034_GSEL_1024X),
+ GAIN_SCALE_GAIN(2048, BU27034_GSEL_2048X),
+ GAIN_SCALE_GAIN(4096, BU27034_GSEL_4096X),
+};
+
+/*
+ * The IC has 5 modes for sampling time. 5 mS mode is exceptional as it limits
+ * the data collection to data0-channel only and cuts the supported range to
+ * 10 bit. It is not aupported by the driver.
+ *
+ * "normal" modes are 55, 100, 200 and 400 mS modes - which do have direct
+ * multiplying impact to the register values similar to gain.
+ *
+ * This means that if meas-mode is changed for example from 400 => 200,
+ * the scale is doubled. Eg, time impact to total gain is x1, x2, x4, x8.
+ */
+#define BU27034_MEAS_MODE_100MS 0
+#define BU27034_MEAS_MODE_55MS 1
+#define BU27034_MEAS_MODE_200MS 2
+#define BU27034_MEAS_MODE_400MS 4
+
+static const struct iio_itime_sel_mul bu27034_itimes[] = {
+ GAIN_SCALE_ITIME_MS(400, BU27034_MEAS_MODE_400MS, 8),
+ GAIN_SCALE_ITIME_MS(200, BU27034_MEAS_MODE_200MS, 4),
+ GAIN_SCALE_ITIME_MS(100, BU27034_MEAS_MODE_100MS, 2),
+ GAIN_SCALE_ITIME_MS(50, BU27034_MEAS_MODE_55MS, 1),
+};
+
+#define BU27034_CHAN_DATA(_name, _ch2) \
+{ \
+ .type = IIO_INTENSITY, \
+ .channel = BU27034_CHAN_##_name, \
+ .channel2 = (_ch2), \
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | \
+ BIT(IIO_CHAN_INFO_SCALE), \
+ .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_INT_TIME), \
+ .address = BU27034_REG_##_name##_LO, \
+ .scan_index = BU27034_CHAN_##_name, \
+ .scan_type = { \
+ .sign = 'u', \
+ .realbits = 16, \
+ .storagebits = 16, \
+ .endianness = IIO_LE, \
+ }, \
+ .indexed = 1 \
+}
+
+static const struct iio_chan_spec bu27034_channels[] = {
+ {
+ .type = IIO_LIGHT,
+ .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
+ .channel = BU27034_CHAN_ALS,
+ },
+ BU27034_CHAN_DATA(DATA0, IIO_MOD_LIGHT_CLEAR),
+ BU27034_CHAN_DATA(DATA1, IIO_MOD_LIGHT_CLEAR),
+ BU27034_CHAN_DATA(DATA2, IIO_MOD_LIGHT_IR),
+};
+
+struct bu27034_data {
+ struct regmap *regmap;
+ struct device *dev;
+ /*
+ * Protect gain and time during scale adjustment and data reading as
+ * well as the channel data 'cached' flag.
+ */
+ struct mutex mutex;
+ struct iio_gts gts;
+ bool cached;
+ __le16 raw[3];
+};
+
+struct bu27034_result {
+ u16 ch0;
+ u16 ch1;
+ u16 ch2;
+};
+
+static const struct regmap_range bu27034_volatile_ranges[] = {
+ {
+ .range_min = BU27034_REG_MODE_CONTROL4,
+ .range_max = BU27034_REG_MODE_CONTROL4,
+ }, {
+ .range_min = BU27034_REG_DATA0_LO,
+ .range_max = BU27034_REG_DATA2_HI,
+ },
+};
+
+static const struct regmap_access_table bu27034_volatile_regs = {
+ .yes_ranges = &bu27034_volatile_ranges[0],
+ .n_yes_ranges = ARRAY_SIZE(bu27034_volatile_ranges),
+};
+
+static const struct regmap_range bu27034_read_only_ranges[] = {
+ {
+ .range_min = BU27034_REG_DATA0_LO,
+ .range_max = BU27034_REG_DATA2_HI,
+ }, {
+ .range_min = BU27034_REG_MANUFACTURER_ID,
+ .range_max = BU27034_REG_MANUFACTURER_ID,
+ }
+};
+
+static const struct regmap_access_table bu27034_ro_regs = {
+ .no_ranges = &bu27034_read_only_ranges[0],
+ .n_no_ranges = ARRAY_SIZE(bu27034_read_only_ranges),
+};
+
+static const struct regmap_config bu27034_regmap = {
+ .reg_bits = 8,
+ .val_bits = 8,
+
+ .max_register = BU27034_REG_MAX,
+ .cache_type = REGCACHE_RBTREE,
+ .volatile_table = &bu27034_volatile_regs,
+};
+
+static int bu27034_validate_int_time(struct bu27034_data *data, int time_us)
+{
+ /*
+ * The BU27034 has 55 mS integration time which is in the vendor tests
+ * handled as 50 mS in all of the internal computations. We keep same
+ * approach here.
+ */
+ if (time_us == 55000)
+ return 50000;
+
+ if (iio_gts_valid_time(&data->gts, time_us))
+ return time_us;
+
+ return -EINVAL;
+}
+
+struct bu27034_gain_check {
+ int old_gain;
+ int new_gain;
+ int chan;
+};
+
+static int bu27034_get_gain_sel(struct bu27034_data *data, int chan)
+{
+ int ret, val;
+
+ switch (chan) {
+ case BU27034_CHAN_DATA0:
+ case BU27034_CHAN_DATA1:
+ {
+ int reg[] = {
+ [BU27034_CHAN_DATA0] = BU27034_REG_MODE_CONTROL2,
+ [BU27034_CHAN_DATA1] = BU27034_REG_MODE_CONTROL3,
+ };
+ ret = regmap_read(data->regmap, reg[chan], &val);
+ if (ret)
+ return ret;
+
+ val &= BU27034_MASK_D01_GAIN;
+ return val >> BU27034_SHIFT_D01_GAIN;
+ }
+ case BU27034_CHAN_DATA2:
+ ret = regmap_read(data->regmap, BU27034_REG_MODE_CONTROL2, &val);
+ if (ret)
+ return ret;
+
+ return (val & BU27034_MASK_D2_GAIN_HI) >> BU27034_SHIFT_D2_GAIN
+ | (val & BU27034_MASK_D2_GAIN_LO);
+ }
+
+ dev_err(data->dev, "Can't get gain for channel %d\n", chan);
+
+ return -EINVAL;
+}
+
+static int bu27034_get_gain(struct bu27034_data *data, int chan, int *gain)
+{
+ int ret, sel;
+
+ ret = bu27034_get_gain_sel(data, chan);
+ if (ret < 0)
+ return ret;
+
+ sel = ret;
+
+ ret = iio_gts_find_gain_by_sel(&data->gts, sel);
+ if (ret < 0)
+ dev_err(data->dev, "chan %u: unknown gain value 0x%x\n", chan,
+ sel);
+
+ *gain = ret;
+
+ return 0;
+}
+
+static int bu27034_get_int_time(struct bu27034_data *data)
+{
+ int ret, sel;
+
+ ret = regmap_read(data->regmap, BU27034_REG_MODE_CONTROL1, &sel);
+ if (ret)
+ return ret;
+
+ return iio_gts_find_int_time_by_sel(&data->gts,
+ sel & BU27034_MASK_MEAS_MODE);
+}
+
+static int _bu27034_get_scale(struct bu27034_data *data, int channel, int *val,
+ int *val2)
+{
+ int gain, ret;
+
+ ret = bu27034_get_gain(data, channel, &gain);
+ if (ret)
+ return ret;
+
+ ret = bu27034_get_int_time(data);
+ if (ret < 0)
+ return ret;
+
+ return iio_gts_get_scale(&data->gts, gain, ret, val, val2);
+}
+
+static int bu27034_get_scale(struct bu27034_data *data, int channel, int *val,
+ int *val2)
+{
+ int ret;
+
+ mutex_lock(&data->mutex);
+ ret = _bu27034_get_scale(data, channel, val, val2);
+ mutex_unlock(&data->mutex);
+
+ return ret;
+}
+
+/* Caller should hold the lock to protect data->cached */
+static int bu27034_write_gain_sel(struct bu27034_data *data, int chan, int sel)
+{
+ static const int reg[] = {
+ [BU27034_CHAN_DATA0] = BU27034_REG_MODE_CONTROL2,
+ [BU27034_CHAN_DATA1] = BU27034_REG_MODE_CONTROL3,
+ [BU27034_CHAN_DATA2] = BU27034_REG_MODE_CONTROL2
+ };
+ int mask;
+
+ if (chan < BU27034_CHAN_DATA0 || chan > BU27034_CHAN_DATA2)
+ return -EINVAL;
+
+ if (chan == BU27034_CHAN_DATA0 || chan == BU27034_CHAN_DATA1) {
+ sel <<= BU27034_SHIFT_D01_GAIN;
+ mask = BU27034_MASK_D01_GAIN;
+ } else {
+ /*
+ * We don't allow setting high bits for DATA2 gain because
+ * that impacts to DATA0 as well.
+ */
+ mask = BU27034_MASK_D2_GAIN_LO;
+ }
+
+ /* We are changing gain so we need to invalidate cached results. */
+ data->cached = false;
+
+ return regmap_update_bits(data->regmap, reg[chan], mask, sel);
+}
+
+static int _bu27034_set_gain(struct bu27034_data *data, int chan, int gain)
+{
+ int ret, sel;
+
+ ret = iio_gts_find_sel_by_gain(&data->gts, gain);
+ if (ret < 0)
+ return ret;
+
+ return bu27034_write_gain_sel(data, chan, sel);
+}
+
+/* Caller should hold the lock to protect data->cached */
+static int bu27034_set_int_time(struct bu27034_data *data, int time)
+{
+ int ret;
+
+ ret = iio_gts_find_sel_by_int_time(&data->gts, time);
+ if (ret < 0)
+ return ret;
+
+ /* We are changing int time so we need to invalidate cached results. */
+ data->cached = false;
+
+ return regmap_update_bits(data->regmap, BU27034_REG_MODE_CONTROL1,
+ BU27034_MASK_MEAS_MODE, ret);
+}
+
+/*
+ * We try to change the time in such way that the scale is maintained for
+ * given channels by adjusting gain so that it compensates the time change.
+ */
+static int bu27034_try_set_int_time(struct bu27034_data *data, int time_us)
+{
+ int ret, int_time_old, int_time_new, i;
+ struct bu27034_gain_check gains[3] = {
+ { .chan = BU27034_CHAN_DATA0, },
+ { .chan = BU27034_CHAN_DATA1, },
+ { .chan = BU27034_CHAN_DATA2 }
+ };
+ int numg = ARRAY_SIZE(gains);
+
+ mutex_lock(&data->mutex);
+ ret = bu27034_get_int_time(data);
+ if (ret < 0)
+ goto unlock_out;
+
+ int_time_old = ret;
+
+ ret = bu27034_validate_int_time(data, time_us);
+ if (ret < 0) {
+ dev_err(data->dev, "Unsupported integration time %u\n",
+ time_us);
+
+ goto unlock_out;
+ }
+
+ int_time_new = ret;
+
+ if (int_time_new == int_time_old) {
+ ret = 0;
+ goto unlock_out;
+ }
+
+ for (i = 0; i < numg; i++) {
+ ret = bu27034_get_gain(data, gains[i].chan,
+ &gains[i].old_gain);
+ if (ret)
+ goto unlock_out;
+
+ gains[i].new_gain = gains[i].old_gain * int_time_old /
+ int_time_new;
+
+ if (!iio_gts_valid_gain(&data->gts, gains[i].new_gain)) {
+ int scale1, scale2;
+
+ _bu27034_get_scale(data, gains[i].chan, &scale1, &scale2);
+ dev_err(data->dev,
+ "chan %u, can't support time %u with scale %u %u\n",
+ gains[i].chan, time_us, scale1, scale2);
+
+ ret = -EINVAL;
+ goto unlock_out;
+ }
+ }
+
+ /*
+ * The new integration time can be supported while keeping the scale of
+ * channels intact by tuning the gains.
+ */
+ for (i = 0; i < numg; i++) {
+ ret = _bu27034_set_gain(data, gains[i].chan, gains[i].new_gain);
+ if (ret)
+ goto unlock_out;
+ }
+
+ ret = bu27034_set_int_time(data, int_time_new);
+
+unlock_out:
+ mutex_unlock(&data->mutex);
+
+ return ret;
+}
+
+static int bu27034_set_scale(struct bu27034_data *data, int chan,
+ int val, int val2)
+{
+ int ret, time_sel, gain_sel, i;
+ bool found = false;
+
+ mutex_lock(&data->mutex);
+ ret = regmap_read(data->regmap, BU27034_REG_MODE_CONTROL1, &time_sel);
+ if (ret)
+ goto unlock_out;
+
+ ret = iio_gts_find_gain_sel_for_scale_using_time(&data->gts, time_sel,
+ val, val2 * 1000, &gain_sel);
+ if (ret) {
+ /* We need to maintain the scale for all channels */
+ int new_time_sel;
+ struct bu27034_gain_check gains[2];
+
+ if (chan == BU27034_CHAN_DATA0) {
+ gains[0].chan = BU27034_CHAN_DATA1;
+ gains[1].chan = BU27034_CHAN_DATA2;
+ } else if (chan == BU27034_CHAN_DATA1) {
+ gains[0].chan = BU27034_CHAN_DATA0;
+ gains[1].chan = BU27034_CHAN_DATA2;
+ } else {
+ gains[0].chan = BU27034_CHAN_DATA0;
+ gains[1].chan = BU27034_CHAN_DATA1;
+ }
+ for (i = 0; i < 2; i++) {
+ ret = bu27034_get_gain(data, gains[i].chan,
+ &gains[i].old_gain);
+ if (ret)
+ goto unlock_out;
+ }
+
+ for (i = 0; i < data->gts.num_itime; i++) {
+ new_time_sel = data->gts.itime_table[i].sel;
+
+ if (new_time_sel == time_sel)
+ continue;
+
+ ret = iio_gts_find_gain_sel_for_scale_using_time(
+ &data->gts, new_time_sel, val, val2 * 1000,
+ &gain_sel);
+ if (ret)
+ continue;
+
+ ret = iio_gts_find_new_gain_sel_by_old_gain_time(
+ &data->gts, gains[0].old_gain, time_sel,
+ new_time_sel, &gains[0].new_gain);
+ if (ret)
+ continue;
+
+ ret = iio_gts_find_new_gain_sel_by_old_gain_time(
+ &data->gts, gains[1].old_gain, time_sel,
+ new_time_sel, &gains[1].new_gain);
+ if (!ret) {
+ found = true;
+ break;
+ }
+ }
+ if (!found) {
+ dev_err(data->dev,
+ "Can't set scale maintaining other channels\n");
+ ret = -EINVAL;
+
+ goto unlock_out;
+ }
+
+ for (i = 0; i < 2; i++) {
+ ret = _bu27034_set_gain(data, gains[0].chan,
+ gains[0].new_gain);
+ if (ret)
+ goto unlock_out;
+
+ ret = _bu27034_set_gain(data, gains[1].chan,
+ gains[1].new_gain);
+ if (ret)
+ goto unlock_out;
+ }
+
+ ret = regmap_update_bits(data->regmap, BU27034_REG_MODE_CONTROL1,
+ BU27034_MASK_MEAS_MODE, new_time_sel);
+ if (ret)
+ goto unlock_out;
+ }
+
+ ret = bu27034_write_gain_sel(data, chan, gain_sel);
+unlock_out:
+ mutex_unlock(&data->mutex);
+
+ return ret;
+}
+
+/*
+ * for (D1/D0 < 0.87):
+ * lx = 0.004521097 * D1 - 0.002663996 * D0 +
+ * 0.00012213 * D1 * D1 / D0
+ *
+ * => 115.7400832 * ch1 / gain1 / mt -
+ * 68.1982976 * ch0 / gain0 / mt +
+ * 0.00012213 * 25600 * (ch1 / gain1 / mt) * 25600 *
+ * (ch1 /gain1 / mt) / (25600 * ch0 / gain0 / mt)
+ *
+ * A = 0.00012213 * 25600 * (ch1 /gain1 / mt) * 25600 *
+ * (ch1 /gain1 / mt) / (25600 * ch0 / gain0 / mt)
+ * => 0.00012213 * 25600 * (ch1 /gain1 / mt) *
+ * (ch1 /gain1 / mt) / (ch0 / gain0 / mt)
+ * => 0.00012213 * 25600 * (ch1 / gain1) * (ch1 /gain1 / mt) /
+ * (ch0 / gain0)
+ * => 0.00012213 * 25600 * (ch1 / gain1) * (ch1 /gain1 / mt) *
+ * gain0 / ch0
+ * => 3.126528 * ch1 * ch1 * gain0 / gain1 / gain1 / mt /ch0
+ *
+ * lx = (115.7400832 * ch1 / gain1 - 68.1982976 * ch0 / gain0) /
+ * mt + A
+ * => (115.7400832 * ch1 / gain1 - 68.1982976 * ch0 / gain0) /
+ * mt + 3.126528 * ch1 * ch1 * gain0 / gain1 / gain1 / mt /
+ * ch0
+ *
+ * => (115.7400832 * ch1 / gain1 - 68.1982976 * ch0 / gain0 +
+ * 3.126528 * ch1 * ch1 * gain0 / gain1 / gain1 / ch0) /
+ * mt
+ *
+ * For (0.87 <= D1/D0 < 1.00)
+ * lx = (0.001331* D0 + 0.0000354 * D1) * ((D1/D0 – 0.87) * (0.385) + 1)
+ * => (0.001331 * 256 * 100 * ch0 / gain0 / mt + 0.0000354 * 256 *
+ * 100 * ch1 / gain1 / mt) * ((D1/D0 - 0.87) * (0.385) + 1)
+ * => (34.0736 * ch0 / gain0 / mt + 0.90624 * ch1 / gain1 / mt) *
+ * ((D1/D0 - 0.87) * (0.385) + 1)
+ * => (34.0736 * ch0 / gain0 / mt + 0.90624 * ch1 / gain1 / mt) *
+ * (0.385 * D1/D0 - 0.66505)
+ * => (34.0736 * ch0 / gain0 / mt + 0.90624 * ch1 / gain1 / mt) *
+ * (0.385 * 256 * 100 * ch1 / gain1 / mt / (256 * 100 * ch0 / gain0 / mt) - 0.66505)
+ * => (34.0736 * ch0 / gain0 / mt + 0.90624 * ch1 / gain1 / mt) *
+ * (9856 * ch1 / gain1 / mt / (25600 * ch0 / gain0 / mt) + 0.66505)
+ * => 13.118336 * ch1 / (gain1 * mt)
+ * + 22.66064768 * ch0 / (gain0 * mt)
+ * + 8931.90144 * ch1 * ch1 * gain0 /
+ * (25600 * ch0 * gain1 * gain1 * mt)
+ * + 0.602694912 * ch1 / (gain1 * mt)
+ *
+ * => [0.3489024 * ch1 * ch1 * gain0 / (ch0 * gain1 * gain1)
+ * + 22.66064768 * ch0 / gain0
+ * + 13.721030912 * ch1 / gain1
+ * ] / mt
+ *
+ * For (D1/D0 >= 1.00)
+ *
+ * lx = (0.001331* D0 + 0.0000354 * D1) * ((D1/D0 – 2.0) * (-0.05) + 1)
+ * => (0.001331* D0 + 0.0000354 * D1) * (-0.05D1/D0 + 1.1)
+ * => (0.001331 * 256 * 100 * ch0 / gain0 / mt + 0.0000354 * 256 *
+ * 100 * ch1 / gain1 / mt) * (-0.05D1/D0 + 1.1)
+ * => (34.0736 * ch0 / gain0 / mt + 0.90624 * ch1 / gain1 / mt) *
+ * (-0.05 * 256 * 100 * ch1 / gain1 / mt / (256 * 100 * ch0 / gain0 / mt) + 1.1)
+ * => (34.0736 * ch0 / gain0 / mt + 0.90624 * ch1 / gain1 / mt) *
+ * (-1280 * ch1 / (gain1 * mt * 25600 * ch0 / gain0 / mt) + 1.1)
+ * => (34.0736 * ch0 * -1280 * ch1 * gain0 * mt /( gain0 * mt * gain1 * mt * 25600 * ch0)
+ * + 34.0736 * 1.1 * ch0 / (gain0 * mt)
+ * + 0.90624 * ch1 * -1280 * ch1 *gain0 * mt / (gain1 * mt *gain1 * mt * 25600 * ch0)
+ * + 1.1 * 0.90624 * ch1 / (gain1 * mt)
+ * => -43614.208 * ch1 / (gain1 * mt * 25600)
+ * + 37.48096 ch0 / (gain0 * mt)
+ * - 1159.9872 * ch1 * ch1 * gain0 / (gain1 * gain1 * mt * 25600 * ch0)
+ * + 0.996864 ch1 / (gain1 * mt)
+ * => [
+ * - 0.045312 * ch1 * ch1 * gain0 / (gain1 * gain1 * ch0)
+ * - 0.706816 * ch1 / gain1
+ * + 37.48096 ch0 /gain0
+ * ] * mt
+ *
+ *
+ * So, the first case (D1/D0 < 0.87) can be computed to a form:
+ *
+ * lx = (3.126528 * ch1 * ch1 * gain0 / (ch0 * gain1 * gain1) +
+ * 115.7400832 * ch1 / gain1 +
+ * -68.1982976 * ch0 / gain0
+ * / mt
+ *
+ * Second case (0.87 <= D1/D0 < 1.00) goes to form:
+ *
+ * => [0.3489024 * ch1 * ch1 * gain0 / (ch0 * gain1 * gain1) +
+ * 13.721030912 * ch1 / gain1 +
+ * 22.66064768 * ch0 / gain0
+ * ] / mt
+ *
+ * Third case (D1/D0 >= 1.00) goes to form:
+ * => [-0.045312 * ch1 * ch1 * gain0 / (ch0 * gain1 * gain1) +
+ * -0.706816 * ch1 / gain1 +
+ * 37.48096 ch0 /(gain0
+ * ] / mt
+ *
+ * This can be unified to format:
+ * lx = [
+ * A * ch1 * ch1 * gain0 / (ch0 * gain1 * gain1) +
+ * B * ch1 / gain1 +
+ * C * ch0 / gain0
+ * ] / mt
+ *
+ * For case 1:
+ * A = 3.126528,
+ * B = 115.7400832
+ * C = -68.1982976
+ *
+ * For case 2:
+ * A = 0.3489024
+ * B = 13.721030912
+ * C = 22.66064768
+ *
+ * For case 3:
+ * A = -0.045312
+ * B = -0.706816
+ * C = 37.48096
+ */
+
+struct bu27034_lx_coeff {
+ unsigned int A;
+ unsigned int B;
+ unsigned int C;
+ /* Indicate which of the coefficients above are negative */
+ bool is_neg[3];
+};
+
+static u64 bu27034_fixp_calc_t1(unsigned int coeff, unsigned int ch0,
+ unsigned int ch1, unsigned int gain0,
+ unsigned int gain1)
+{
+ unsigned int helper, tmp;
+ u64 helper64;
+
+ /*
+ * Here we could overflow even the 64bit value. Hence we
+ * multiply with gain0 only after the divisions - even though
+ * it may result loss of accuracy
+ */
+ helper64 = (u64)coeff * (u64)ch1 * (u64)ch1; /* * (u64)gain0 */
+ helper = coeff * ch1 * ch1; /* * gain0*/
+ tmp = helper * gain0;
+
+ if (helper == helper64 && (tmp / gain0 == helper))
+ return tmp / (gain1 * gain1) / ch0;
+
+ helper = gain1 * gain1;
+ if (helper > ch0) {
+ do_div(helper64, helper);
+ /*
+ * multiplication with max gain may overflow
+ * if helper64 is greater than 0xFFFFFFFFFFFFF.
+ *
+ * If this is the case we divide first.
+ */
+ if (helper64 < 0xFFFFFFFFFFFFFLLU) {
+ helper64 *= gain0;
+ do_div(helper64, ch0);
+ } else {
+ do_div(helper64, ch0);
+ helper64 *= gain0;
+ }
+
+ return helper64;
+ }
+
+ do_div(helper64, ch0);
+ /* Same overflow check here */
+ if (helper64 < 0xFFFFFFFFFFFFFLLU) {
+ helper64 *= gain0;
+ do_div(helper64, helper);
+ } else {
+ do_div(helper64, helper);
+ helper64 *= gain0;
+ }
+
+ return helper64;
+}
+
+static u64 bu27034_fixp_calc_t23(unsigned int coeff, unsigned int ch,
+ unsigned int gain)
+{
+ unsigned int helper;
+ u64 helper64;
+
+ helper64 = (u64)coeff * (u64)ch;
+ helper = coeff * ch;
+
+ if (helper == helper64)
+ return helper / gain;
+
+ do_div(helper64, gain);
+
+ return helper64;
+}
+
+static int bu27034_fixp_calc_lx(unsigned int ch0, unsigned int ch1,
+ unsigned int gain0, unsigned int gain1,
+ unsigned int meastime, int coeff_idx)
+{
+ static const struct bu27034_lx_coeff coeff[] = {
+ {
+ .A = 31265280, /* 3.126528 */
+ .B = 1157400832, /*115.7400832 */
+ .C = 681982976, /* -68.1982976 */
+ .is_neg = {false, false, true},
+ }, {
+ .A = 3489024, /* 0.3489024 */
+ .B = 137210309, /* 13.721030912 */
+ .C = 226606476, /* 22.66064768 */
+ /* All terms positive */
+ }, {
+ .A = 453120, /* -0.045312 */
+ .B = 7068160, /* -0.706816 */
+ .C = 374809600, /* 37.48096 */
+ .is_neg = {true, true, false},
+ }
+ };
+ const struct bu27034_lx_coeff *c = &coeff[coeff_idx];
+ u64 res = 0, terms[3];
+ int i;
+
+ if (coeff_idx >= ARRAY_SIZE(coeff))
+ return -EINVAL;
+
+ terms[0] = bu27034_fixp_calc_t1(c->A, ch0, ch1, gain0, gain1);
+ terms[1] = bu27034_fixp_calc_t23(c->B, ch1, gain1);
+ terms[2] = bu27034_fixp_calc_t23(c->C, ch0, gain0);
+
+ /* First, add positive terms */
+ for (i = 0; i < 3; i++)
+ if (!c->is_neg[i])
+ res += terms[i];
+
+ /* No positive term => zero lux */
+ if (!res)
+ return 0;
+
+ /* Then, subtract negative terms (if any) */
+ for (i = 0; i < 3; i++)
+ if (c->is_neg[i]) {
+ /*
+ * If the negative term is greater than positive - then
+ * the darknes has taken over and we are all doomed! Eh,
+ * I mean, then we can just return 0 lx and go out
+ */
+ if (terms[i] >= res)
+ return 0;
+
+ res -= terms[i];
+ }
+
+ meastime *= 10000;
+ do_div(res, meastime);
+
+ return (int) res;
+}
+
+static bool bu27034_has_valid_sample(struct bu27034_data *data)
+{
+ int ret, val;
+
+ ret = regmap_read(data->regmap, BU27034_REG_MODE_CONTROL4, &val);
+ if (ret)
+ dev_err(data->dev, "Read failed %d\n", ret);
+
+ return (val & BU27034_MASK_VALID);
+}
+
+static void bu27034_invalidate_read_data(struct bu27034_data *data)
+{
+ bu27034_has_valid_sample(data);
+}
+
+static int _bu27034_get_result(struct bu27034_data *data, u16 *res, bool lock)
+{
+ int ret = 0;
+
+retry:
+ if (lock)
+ mutex_lock(&data->mutex);
+ /* Get new value from sensor if data is ready - or use cached value */
+ if (bu27034_has_valid_sample(data)) {
+ ret = regmap_bulk_read(data->regmap, BU27034_REG_DATA0_LO,
+ &data->raw[0], sizeof(data->raw));
+ if (ret)
+ goto unlock_out;
+
+ data->cached = true;
+ bu27034_invalidate_read_data(data);
+ } else if (unlikely(!data->cached)) {
+ /* No new data in sensor and no value cached. Wait and retry */
+ if (lock)
+ mutex_unlock(&data->mutex);
+ msleep(25);
+
+ goto retry;
+ }
+ res[0] = le16_to_cpu(data->raw[0]);
+ res[1] = le16_to_cpu(data->raw[1]);
+ res[2] = le16_to_cpu(data->raw[2]);
+
+unlock_out:
+ if (lock)
+ mutex_unlock(&data->mutex);
+
+ return ret;
+}
+
+static int bu27034_get_result_unlocked(struct bu27034_data *data, u16 *res)
+{
+ return _bu27034_get_result(data, res, false);
+}
+
+static int bu27034_get_result(struct bu27034_data *data, u16 *res)
+{
+ return _bu27034_get_result(data, res, true);
+}
+
+/*
+ * The formula given by vendor for computing luxes out of data0 and data1
+ * (in open air) is as follows:
+ *
+ * Let's mark:
+ * D0 = data0/ch0_gain/meas_time_ms * 25600
+ * D1 = data1/ch1_gain/meas_time_ms * 25600
+ *
+ * Then:
+ * if (D1/D0 < 0.87)
+ * lx = (0.001331 * D0 + 0.0000354 * D1) * ((D1 / D0 - 0.87) * 3.45 + 1)
+ * else if (D1/D0 < 1)
+ * lx = (0.001331 * D0 + 0.0000354 * D1) * ((D1 / D0 - 0.87) * 0.385 + 1)
+ * else
+ * lx = (0.001331 * D0 + 0.0000354 * D1) * ((D1 / D0 - 2) * -0.05 + 1)
+ *
+ * we try implementing it here. Users who have for example some colored lens
+ * need to modify the calculation but I hope this gives a starting point for
+ * those working with such devices.
+ *
+ * The first case (D1/D0 < 0.87) can be computed to a form:
+ * lx = 0.004521097 * D1 - 0.002663996 * D0 + 0.00012213 * D1 * D1 / D0
+ */
+static int bu27034_get_lux(struct bu27034_data *data, int *val)
+{
+ unsigned int gain0, gain1, meastime;
+ unsigned int d1_d0_ratio_scaled;
+ u16 res[3], ch0, ch1;
+ u64 helper64;
+ int ret;
+
+ mutex_lock(&data->mutex);
+ ret = bu27034_get_result_unlocked(data, &res[0]);
+ if (ret)
+ goto unlock_out;
+
+ /* Avoid div by zero */
+ if (!res[0])
+ ch0 = 1;
+ else
+ ch0 = res[0];
+
+ if (!res[1])
+ ch1 = 1;
+ else
+ ch1 = res[1];
+
+
+ ret = bu27034_get_gain(data, BU27034_CHAN_DATA0, &gain0);
+ if (ret)
+ goto unlock_out;
+
+ ret = bu27034_get_gain(data, BU27034_CHAN_DATA1, &gain1);
+ if (ret)
+ goto unlock_out;
+
+ ret = bu27034_get_int_time(data);
+ if (ret < 0)
+ goto unlock_out;
+
+ meastime = ret;
+
+ mutex_unlock(&data->mutex);
+
+ d1_d0_ratio_scaled = (unsigned int)ch1 * (unsigned int)gain0 * 100;
+ helper64 = (u64)ch1 * (u64)gain0 * 100LLU;
+
+ if (helper64 != d1_d0_ratio_scaled) {
+ unsigned int div = (unsigned int)ch0 * gain1;
+
+ do_div(helper64, div);
+ d1_d0_ratio_scaled = helper64;
+ } else {
+ d1_d0_ratio_scaled /= ch0 * gain1;
+ }
+
+ if (d1_d0_ratio_scaled < 87)
+ *val = bu27034_fixp_calc_lx(ch0, ch1, gain0, gain1, meastime, 0);
+ else if (d1_d0_ratio_scaled < 100)
+ *val = bu27034_fixp_calc_lx(ch0, ch1, gain0, gain1, meastime, 1);
+ else
+ *val = bu27034_fixp_calc_lx(ch0, ch1, gain0, gain1, meastime, 2);
+
+ return 0;
+
+unlock_out:
+ mutex_unlock(&data->mutex);
+
+ return ret;
+}
+
+static int bu27034_meas_set(struct bu27034_data *data, bool en)
+{
+ int ret;
+
+ mutex_lock(&data->mutex);
+ if (en)
+ ret = regmap_set_bits(data->regmap, BU27034_REG_MODE_CONTROL4,
+ BU27034_MASK_MEAS_EN);
+ else
+ ret = regmap_clear_bits(data->regmap, BU27034_REG_MODE_CONTROL4,
+ BU27034_MASK_MEAS_EN);
+ mutex_unlock(&data->mutex);
+
+ return ret;
+}
+
+static int bu27034_meas_en(struct bu27034_data *data)
+{
+ return bu27034_meas_set(data, true);
+}
+
+static int bu27034_meas_dis(struct bu27034_data *data)
+{
+ return bu27034_meas_set(data, false);
+}
+
+static int bu27034_read_raw(struct iio_dev *idev,
+ struct iio_chan_spec const *chan,
+ int *val, int *val2, long mask)
+{
+ struct bu27034_data *data = iio_priv(idev);
+ int ret;
+
+ switch (mask) {
+ case IIO_CHAN_INFO_INT_TIME:
+ *val = 0;
+
+ ret = bu27034_get_int_time(data);
+ if (ret < 0)
+ return ret;
+
+ /*
+ * We use 50000 uS internally for all calculations and only
+ * convert it to 55000 before returning it to the user.
+ *
+ * This is becaise data-sheet says the time is 55 mS - but
+ * vendor provided computations used 50 mS.
+ */
+ if (ret == 50000)
+ ret = 55000;
+
+ *val2 = 0;
+ *val = ret;
+
+ return IIO_VAL_INT_PLUS_MICRO;
+
+ case IIO_CHAN_INFO_SCALE:
+ ret = bu27034_get_scale(data, chan->channel, val, val2);
+ if (ret)
+ return ret;
+
+ return IIO_VAL_INT_PLUS_NANO;
+
+ case IIO_CHAN_INFO_RAW:
+ {
+ u16 res[3];
+
+ if (chan->type != IIO_INTENSITY)
+ return -EINVAL;
+
+ if (chan->channel < BU27034_CHAN_DATA0 ||
+ chan->channel > BU27034_CHAN_DATA2)
+ return -EINVAL;
+ /*
+ * Reading one channel at a time is inefficient.
+ *
+ * Hence we run the measurement on the background and always
+ * read all the channels. There are following caveats:
+ * 1) The VALID bit handling is racy. Valid bit clearing is not
+ * tied to reading the data in the hardware. We clear the
+ * valid-bit manually _after_ we have read the data - but this
+ * means there is a small time-window where new result may
+ * arrive between read and clear. This means we can miss a
+ * sample. For normal use this should not be fatal because
+ * usually the light is changing slowly. There might be
+ * use-cases for measuring more rapidly changing light but this
+ * driver is unsuitable for those cases anyways. (Smallest
+ * measurement time we support is 55 mS.)
+ * 2) Data readings more frequent than the meas_time will return
+ * the same cached values. This should not be a problem for the
+ * very same reason 1) is not a problem.
+ */
+ ret = bu27034_get_result(data, &res[0]);
+ if (ret)
+ return ret;
+
+ *val = res[chan->channel - BU27034_CHAN_DATA0];
+
+ return IIO_VAL_INT;
+ }
+
+ case IIO_CHAN_INFO_PROCESSED:
+ if (chan->type != IIO_LIGHT)
+ return -EINVAL;
+
+ ret = bu27034_get_lux(data, val);
+ if (ret)
+ return ret;
+ return IIO_VAL_INT;
+
+ }
+
+ return -EINVAL;
+}
+
+static int bu27034_write_raw(struct iio_dev *idev,
+ struct iio_chan_spec const *chan,
+ int val, int val2, long mask)
+{
+ struct bu27034_data *data = iio_priv(idev);
+
+ switch (mask) {
+ case IIO_CHAN_INFO_SCALE:
+ return bu27034_set_scale(data, chan->channel, val, val2);
+ case IIO_CHAN_INFO_INT_TIME:
+ return bu27034_try_set_int_time(data, val);
+ }
+
+ return -EINVAL;
+}
+
+static const struct iio_info bu27034_info = {
+ .read_raw = &bu27034_read_raw,
+ .write_raw = &bu27034_write_raw,
+};
+
+static void bu27034_meas_stop(void *data)
+{
+ bu27034_meas_dis(data);
+}
+
+static int bu27034_chip_init(struct bu27034_data *data)
+{
+ int ret;
+
+ /* Reset */
+ ret = regmap_update_bits(data->regmap, BU27034_REG_SYSTEM_CONTROL,
+ BU27034_MASK_SW_RESET, BU27034_MASK_SW_RESET);
+ if (ret)
+ return dev_err_probe(data->dev, ret, "Sensor reset failed\n");
+
+ /*
+ * Delay to allow IC to initialize. We don't care if we delay
+ * for more than 1 ms so msleep() is Ok. We just don't want to
+ * block
+ */
+ msleep(1);
+
+ /*
+ * Consider disabling the measurement (and powering off the sensor) for
+ * runtime pm
+ */
+ ret = bu27034_meas_en(data);
+ if (ret)
+ return ret;
+
+ return devm_add_action_or_reset(data->dev, bu27034_meas_stop, data);
+}
+
+static int bu27034_probe(struct i2c_client *i2c)
+{
+ struct device *dev = &i2c->dev;
+ struct fwnode_handle *fwnode;
+ struct bu27034_data *data;
+ struct regmap *regmap;
+ struct iio_dev *idev;
+ unsigned int part_id;
+ int ret;
+
+ regmap = devm_regmap_init_i2c(i2c, &bu27034_regmap);
+ if (IS_ERR(regmap))
+ return dev_err_probe(dev, PTR_ERR(regmap),
+ "Failed to initialize Regmap\n");
+
+ fwnode = dev_fwnode(dev);
+ if (!fwnode)
+ return -ENODEV;
+
+ idev = devm_iio_device_alloc(dev, sizeof(*data));
+ if (!idev)
+ return -ENOMEM;
+
+ ret = devm_regulator_get_enable_optional(dev, "vdd");
+ if (ret != -ENODEV)
+ return dev_err_probe(dev, ret, "Failed to get regulator\n");
+
+ data = iio_priv(idev);
+
+ ret = regmap_read(regmap, BU27034_REG_SYSTEM_CONTROL, &part_id);
+ if (ret)
+ return dev_err_probe(dev, ret, "Failed to access sensor\n");
+
+ part_id &= BU27034_MASK_PART_ID;
+
+ if (part_id != BU27034_ID) {
+ dev_err(dev, "unsupported device 0x%x\n", part_id);
+ return -EINVAL;
+ }
+
+ ret = iio_init_iio_gts(BU27034_SCALE_1X, 0, bu27034_gains,
+ ARRAY_SIZE(bu27034_gains), bu27034_itimes,
+ ARRAY_SIZE(bu27034_itimes), &data->gts);
+ if (ret)
+ return ret;
+
+ mutex_init(&data->mutex);
+ data->regmap = regmap;
+ data->dev = dev;
+
+ idev->channels = bu27034_channels;
+ idev->num_channels = ARRAY_SIZE(bu27034_channels);
+ idev->name = "bu27034-als";
+ idev->info = &bu27034_info;
+
+ idev->modes = INDIO_DIRECT_MODE;
+
+ ret = bu27034_chip_init(data);
+ if (ret)
+ return ret;
+
+ ret = devm_iio_device_register(data->dev, idev);
+ if (ret < 0)
+ return dev_err_probe(dev, ret,
+ "Unable to register iio device\n");
+
+ return ret;
+}
+
+static const struct of_device_id bu27034_of_match[] = {
+ { .compatible = "rohm,bu27034", },
+ { }
+};
+MODULE_DEVICE_TABLE(of, bu27034_of_match);
+
+static struct i2c_driver bu27034_i2c_driver = {
+ .driver = {
+ .name = "bu27034-i2c",
+ .of_match_table = bu27034_of_match,
+ },
+ .probe_new = bu27034_probe,
+};
+module_i2c_driver(bu27034_i2c_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Matti Vaittinen <matti.vaittinen@xxxxxxxxxxxxxxxxx>");
+MODULE_DESCRIPTION("ROHM BU27034 ambient light sensor driver");
--
2.39.2


--
Matti Vaittinen, Linux device drivers
ROHM Semiconductors, Finland SWDC
Kiviharjunlenkki 1E
90220 OULU
FINLAND

~~~ "I don't think so," said Rene Descartes. Just then he vanished ~~~
Simon says - in Latin please.
~~~ "non cogito me" dixit Rene Descarte, deinde evanescavit ~~~
Thanks to Simon Glass for the translation =]

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