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linux-zen-desktop/drivers/iio/light/rohm-bu27034.c

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6.5.5
2023-10-24 12:59:35 +02:00
// 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/bitfield.h>
#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/buffer.h>
#include <linux/iio/iio.h>
#include <linux/iio/iio-gts-helper.h>
#include <linux/iio/kfifo_buf.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_MASK_D2_GAIN_HI GENMASK(7, 6)
#define BU27034_MASK_D2_GAIN_LO GENMASK(2, 0)
#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
/*
* The BU27034 does not have interrupt to trigger the data read when a
* measurement has finished. Hence we poll the VALID bit in a thread. We will
* try to wake the thread BU27034_MEAS_WAIT_PREMATURE_MS milliseconds before
* the expected sampling time to prevent the drifting.
*
* If we constantly wake up a bit too late we would eventually skip a sample.
* And because the sleep can't wake up _exactly_ at given time this would be
* inevitable even if the sensor clock would be perfectly phase-locked to CPU
* clock - which we can't say is the case.
*
* This is still fragile. No matter how big advance do we have, we will still
* risk of losing a sample because things can in a rainy-day scenario be
* delayed a lot. Yet, more we reserve the time for polling, more we also lose
* the performance by spending cycles polling the register. So, selecting this
* value is a balancing dance between severity of wasting CPU time and severity
* of losing samples.
*
* In most cases losing the samples is not _that_ crucial because light levels
* tend to change slowly.
*
* Other option that was pointed to me would be always sleeping 1/2 of the
* measurement time, checking the VALID bit and just sleeping again if the bit
* was not set. That should be pretty tolerant against missing samples due to
* the scheduling delays while also not wasting much of cycles for polling.
* Downside is that the time-stamps would be very inaccurate as the wake-up
* would not really be tied to the sensor toggling the valid bit. This would also
* result 'jumps' in the time-stamps when the delay drifted so that wake-up was
* performed during the consecutive wake-ups (Or, when sensor and CPU clocks
* were very different and scheduling the wake-ups was very close to given
* timeout - and when the time-outs were very close to the actual sensor
* sampling, Eg. once in a blue moon, two consecutive time-outs would occur
* without having a sample ready).
*/
#define BU27034_MEAS_WAIT_PREMATURE_MS 5
#define BU27034_DATA_WAIT_TIME_US 1000
#define BU27034_TOTAL_DATA_WAIT_TIME_US (BU27034_MEAS_WAIT_PREMATURE_MS * 1000)
#define BU27034_RETRY_LIMIT 18
enum {
BU27034_CHAN_ALS,
BU27034_CHAN_DATA0,
BU27034_CHAN_DATA1,
BU27034_CHAN_DATA2,
BU27034_NUM_CHANS
};
static const unsigned long bu27034_scan_masks[] = {
GENMASK(BU27034_CHAN_DATA2, BU27034_CHAN_ALS), 0
};
/*
* 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
/* See the data sheet for the "Gain Setting" table */
#define BU27034_GSEL_1X 0x00 /* 00000 */
#define BU27034_GSEL_4X 0x08 /* 01000 */
#define BU27034_GSEL_16X 0x0a /* 01010 */
#define BU27034_GSEL_32X 0x0b /* 01011 */
#define BU27034_GSEL_64X 0x0c /* 01100 */
#define BU27034_GSEL_256X 0x18 /* 11000 */
#define BU27034_GSEL_512X 0x19 /* 11001 */
#define BU27034_GSEL_1024X 0x1a /* 11010 */
#define BU27034_GSEL_2048X 0x1b /* 11011 */
#define BU27034_GSEL_4096X 0x1c /* 11100 */
/* 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 supported 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_US(400000, BU27034_MEAS_MODE_400MS, 8),
GAIN_SCALE_ITIME_US(200000, BU27034_MEAS_MODE_200MS, 4),
GAIN_SCALE_ITIME_US(100000, BU27034_MEAS_MODE_100MS, 2),
GAIN_SCALE_ITIME_US(55000, 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_separate_available = BIT(IIO_CHAN_INFO_SCALE), \
.info_mask_shared_by_all = BIT(IIO_CHAN_INFO_INT_TIME), \
.info_mask_shared_by_all_available = \
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_RAW) |
BIT(IIO_CHAN_INFO_SCALE),
.channel = BU27034_CHAN_ALS,
.scan_index = BU27034_CHAN_ALS,
.scan_type = {
.sign = 'u',
.realbits = 32,
.storagebits = 32,
.endianness = IIO_CPU,
},
},
/*
* The BU27034 DATA0 and DATA1 channels are both on the visible light
* area (mostly). The data0 sensitivity peaks at 500nm, DATA1 at 600nm.
* These wave lengths are pretty much on the border of colours making
* these a poor candidates for R/G/B standardization. Hence they're both
* marked as clear channels
*/
BU27034_CHAN_DATA(DATA0, IIO_MOD_LIGHT_CLEAR),
BU27034_CHAN_DATA(DATA1, IIO_MOD_LIGHT_CLEAR),
BU27034_CHAN_DATA(DATA2, IIO_MOD_LIGHT_IR),
IIO_CHAN_SOFT_TIMESTAMP(4),
};
struct bu27034_data {
struct regmap *regmap;
struct device *dev;
/*
* Protect gain and time during scale adjustment and data reading.
* Protect measurement enabling/disabling.
*/
struct mutex mutex;
struct iio_gts gts;
struct task_struct *task;
__le16 raw[3];
struct {
u32 mlux;
__le16 channels[3];
s64 ts __aligned(8);
} scan;
};
struct bu27034_result {
u16 ch0;
u16 ch1;
u16 ch2;
};
static const struct regmap_range bu27034_volatile_ranges[] = {
{
.range_min = BU27034_REG_SYSTEM_CONTROL,
.range_max = BU27034_REG_SYSTEM_CONTROL,
}, {
.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,
.wr_table = &bu27034_ro_regs,
};
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;
return FIELD_GET(BU27034_MASK_D01_GAIN, val);
}
case BU27034_CHAN_DATA2:
{
int d2_lo_bits = fls(BU27034_MASK_D2_GAIN_LO);
ret = regmap_read(data->regmap, BU27034_REG_MODE_CONTROL2, &val);
if (ret)
return ret;
/*
* The data2 channel gain is composed by 5 non continuous bits
* [7:6], [2:0]. Thus when we combine the 5-bit 'selector'
* from register value we must right shift the high bits by 3.
*/
return FIELD_GET(BU27034_MASK_D2_GAIN_HI, val) << d2_lo_bits |
FIELD_GET(BU27034_MASK_D2_GAIN_LO, val);
}
default:
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);
return ret;
}
*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;
if (channel == BU27034_CHAN_ALS) {
*val = 0;
*val2 = 1000;
return IIO_VAL_INT_PLUS_MICRO;
}
mutex_lock(&data->mutex);
ret = _bu27034_get_scale(data, channel, val, val2);
mutex_unlock(&data->mutex);
if (ret)
return ret;
return IIO_VAL_INT_PLUS_NANO;
}
/* Caller should hold the lock to protect lux reading */
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,
};
int mask, val;
if (chan != BU27034_CHAN_DATA0 && chan != BU27034_CHAN_DATA1)
return -EINVAL;
val = FIELD_PREP(BU27034_MASK_D01_GAIN, sel);
mask = BU27034_MASK_D01_GAIN;
if (chan == BU27034_CHAN_DATA0) {
/*
* We keep the same gain for channel 2 as we set for channel 0
* We can't allow them to be individually controlled because
* setting one will impact also the other. Also, if we don't
* always update both gains we may result unsupported bit
* combinations.
*
* This is not nice but this is yet another place where the
* user space must be prepared to surprizes. Namely, see chan 2
* gain changed when chan 0 gain is changed.
*
* This is not fatal for most users though. I don't expect the
* channel 2 to be used in any generic cases - the intensity
* values provided by the sensor for IR area are not openly
* documented. Also, channel 2 is not used for visible light.
*
* So, if there is application which is written to utilize the
* channel 2 - then it is probably specifically targeted to this
* sensor and knows how to utilize those values. It is safe to
* hope such user can also cope with the gain changes.
*/
mask |= BU27034_MASK_D2_GAIN_LO;
/*
* The D2 gain bits are directly the lowest bits of selector.
* Just do add those bits to the value
*/
val |= sel & BU27034_MASK_D2_GAIN_LO;
}
return regmap_update_bits(data->regmap, reg[chan], mask, val);
}
static int bu27034_set_gain(struct bu27034_data *data, int chan, int gain)
{
int ret;
/*
* We don't allow setting channel 2 gain as it messes up the
* gain for channel 0 - which shares the high bits
*/
if (chan != BU27034_CHAN_DATA0 && chan != BU27034_CHAN_DATA1)
return -EINVAL;
ret = iio_gts_find_sel_by_gain(&data->gts, gain);
if (ret < 0)
return ret;
return bu27034_write_gain_sel(data, chan, ret);
}
/* Caller should hold the lock to protect data->int_time */
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;
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)
{
struct bu27034_gain_check gains[] = {
{ .chan = BU27034_CHAN_DATA0 },
{ .chan = BU27034_CHAN_DATA1 },
};
int numg = ARRAY_SIZE(gains);
int ret, int_time_old, i;
mutex_lock(&data->mutex);
ret = bu27034_get_int_time(data);
if (ret < 0)
goto unlock_out;
int_time_old = ret;
if (!iio_gts_valid_time(&data->gts, time_us)) {
dev_err(data->dev, "Unsupported integration time %u\n",
time_us);
ret = -EINVAL;
goto unlock_out;
}
if (time_us == 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;
ret = iio_gts_find_new_gain_by_old_gain_time(&data->gts,
gains[i].old_gain,
int_time_old, time_us,
&gains[i].new_gain);
if (ret) {
int scale1, scale2;
bool ok;
_bu27034_get_scale(data, gains[i].chan, &scale1, &scale2);
dev_dbg(data->dev,
"chan %u, can't support time %u with scale %u %u\n",
gains[i].chan, time_us, scale1, scale2);
if (gains[i].new_gain < 0)
goto unlock_out;
/*
* If caller requests for integration time change and we
* can't support the scale - then the caller should be
* prepared to 'pick up the pieces and deal with the
* fact that the scale changed'.
*/
ret = iio_find_closest_gain_low(&data->gts,
gains[i].new_gain, &ok);
if (!ok)
dev_dbg(data->dev,
"optimal gain out of range for chan %u\n",
gains[i].chan);
if (ret < 0) {
dev_dbg(data->dev,
"Total gain increase. Risk of saturation");
ret = iio_gts_get_min_gain(&data->gts);
if (ret < 0)
goto unlock_out;
}
dev_dbg(data->dev, "chan %u scale changed\n",
gains[i].chan);
gains[i].new_gain = ret;
dev_dbg(data->dev, "chan %u new gain %u\n",
gains[i].chan, gains[i].new_gain);
}
}
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, time_us);
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;
if (chan == BU27034_CHAN_DATA2)
return -EINVAL;
if (chan == BU27034_CHAN_ALS) {
if (val == 0 && val2 == 1000000)
return 0;
return -EINVAL;
}
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, &gain_sel);
if (ret) {
/*
* Could not support scale with given time. Need to change time.
* We still want to maintain the scale for all channels
*/
struct bu27034_gain_check gain;
int new_time_sel;
/*
* Populate information for the other channel which should also
* maintain the scale. (Due to the HW limitations the chan2
* gets the same gain as chan0, so we only need to explicitly
* set the chan 0 and 1).
*/
if (chan == BU27034_CHAN_DATA0)
gain.chan = BU27034_CHAN_DATA1;
else if (chan == BU27034_CHAN_DATA1)
gain.chan = BU27034_CHAN_DATA0;
ret = bu27034_get_gain(data, gain.chan, &gain.old_gain);
if (ret)
goto unlock_out;
/*
* Iterate through all the times to see if we find one which
* can support requested scale for requested channel, while
* maintaining the scale for other channels
*/
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;
/* Can we provide requested scale with this time? */
ret = iio_gts_find_gain_sel_for_scale_using_time(
&data->gts, new_time_sel, val, val2,
&gain_sel);
if (ret)
continue;
/* Can the other channel(s) maintain scale? */
ret = iio_gts_find_new_gain_sel_by_old_gain_time(
&data->gts, gain.old_gain, time_sel,
new_time_sel, &gain.new_gain);
if (!ret) {
/* Yes - we found suitable time */
found = true;
break;
}
}
if (!found) {
dev_dbg(data->dev,
"Can't set scale maintaining other channels\n");
ret = -EINVAL;
goto unlock_out;
}
ret = bu27034_set_gain(data, gain.chan, gain.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 inline u64 gain_mul_div_helper(u64 val, unsigned int gain,
unsigned int div)
{
/*
* Max gain for a channel is 4096. The max u64 (0xffffffffffffffffULL)
* divided by 4096 is 0xFFFFFFFFFFFFF (GENMASK_ULL(51, 0)) (floored).
* Thus, the 0xFFFFFFFFFFFFF is the largest value we can safely multiply
* with the gain, no matter what gain is set.
*
* So, multiplication with max gain may overflow if val is greater than
* 0xFFFFFFFFFFFFF (52 bits set)..
*
* If this is the case we divide first.
*/
if (val < GENMASK_ULL(51, 0)) {
val *= gain;
do_div(val, div);
} else {
do_div(val, div);
val *= gain;
}
return val;
}
static u64 bu27034_fixp_calc_t1_64bit(unsigned int coeff, unsigned int ch0,
unsigned int ch1, unsigned int gain0,
unsigned int gain1)
{
unsigned int helper;
u64 helper64;
helper64 = (u64)coeff * (u64)ch1 * (u64)ch1;
helper = gain1 * gain1;
if (helper > ch0) {
do_div(helper64, helper);
return gain_mul_div_helper(helper64, gain0, ch0);
}
do_div(helper64, ch0);
return gain_mul_div_helper(helper64, gain0, helper);
}
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;
/*
* 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
*/
helper = coeff * ch1 * ch1;
tmp = helper * gain0;
helper = ch1 * ch1;
if (check_mul_overflow(helper, coeff, &helper))
return bu27034_fixp_calc_t1_64bit(coeff, ch0, ch1, gain0, gain1);
if (check_mul_overflow(helper, gain0, &tmp))
return bu27034_fixp_calc_t1_64bit(coeff, ch0, ch1, gain0, gain1);
return tmp / (gain1 * gain1) / ch0;
}
static u64 bu27034_fixp_calc_t23(unsigned int coeff, unsigned int ch,
unsigned int gain)
{
unsigned int helper;
u64 helper64;
if (!check_mul_overflow(coeff, ch, &helper))
return helper / gain;
helper64 = (u64)coeff * (u64)ch;
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 darkness 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 *= 10;
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 false;
}
return val & BU27034_MASK_VALID;
}
/*
* Reading the register where VALID bit is clears this bit. (So does changing
* any gain / integration time configuration registers) The bit gets
* set when we have acquired new data. We use this bit to indicate data
* validity.
*/
static void bu27034_invalidate_read_data(struct bu27034_data *data)
{
bu27034_has_valid_sample(data);
}
static int bu27034_read_result(struct bu27034_data *data, int chan, int *res)
{
int reg[] = {
[BU27034_CHAN_DATA0] = BU27034_REG_DATA0_LO,
[BU27034_CHAN_DATA1] = BU27034_REG_DATA1_LO,
[BU27034_CHAN_DATA2] = BU27034_REG_DATA2_LO,
};
int valid, ret;
__le16 val;
ret = regmap_read_poll_timeout(data->regmap, BU27034_REG_MODE_CONTROL4,
valid, (valid & BU27034_MASK_VALID),
BU27034_DATA_WAIT_TIME_US, 0);
if (ret)
return ret;
ret = regmap_bulk_read(data->regmap, reg[chan], &val, sizeof(val));
if (ret)
return ret;
*res = le16_to_cpu(val);
return 0;
}
static int bu27034_get_result_unlocked(struct bu27034_data *data, __le16 *res,
int size)
{
int ret = 0, retry_cnt = 0;
retry:
/* Get new value from sensor if data is ready */
if (bu27034_has_valid_sample(data)) {
ret = regmap_bulk_read(data->regmap, BU27034_REG_DATA0_LO,
res, size);
if (ret)
return ret;
bu27034_invalidate_read_data(data);
} else {
/* No new data in sensor. Wait and retry */
retry_cnt++;
if (retry_cnt > BU27034_RETRY_LIMIT) {
dev_err(data->dev, "No data from sensor\n");
return -ETIMEDOUT;
}
msleep(25);
goto retry;
}
return ret;
}
static int bu27034_meas_set(struct bu27034_data *data, bool en)
{
if (en)
return regmap_set_bits(data->regmap, BU27034_REG_MODE_CONTROL4,
BU27034_MASK_MEAS_EN);
return regmap_clear_bits(data->regmap, BU27034_REG_MODE_CONTROL4,
BU27034_MASK_MEAS_EN);
}
static int bu27034_get_single_result(struct bu27034_data *data, int chan,
int *val)
{
int ret;
if (chan < BU27034_CHAN_DATA0 || chan > BU27034_CHAN_DATA2)
return -EINVAL;
ret = bu27034_meas_set(data, true);
if (ret)
return ret;
ret = bu27034_get_int_time(data);
if (ret < 0)
return ret;
msleep(ret / 1000);
return bu27034_read_result(data, chan, val);
}
/*
* 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 use 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.
*/
static int bu27034_calc_mlux(struct bu27034_data *data, __le16 *res, int *val)
{
unsigned int gain0, gain1, meastime;
unsigned int d1_d0_ratio_scaled;
u16 ch0, ch1;
u64 helper64;
int ret;
/*
* We return 0 lux if calculation fails. This should be reasonably
* easy to spot from the buffers especially if raw-data channels show
* valid values
*/
*val = 0;
ch0 = max_t(u16, 1, le16_to_cpu(res[0]));
ch1 = max_t(u16, 1, le16_to_cpu(res[1]));
ret = bu27034_get_gain(data, BU27034_CHAN_DATA0, &gain0);
if (ret)
return ret;
ret = bu27034_get_gain(data, BU27034_CHAN_DATA1, &gain1);
if (ret)
return ret;
ret = bu27034_get_int_time(data);
if (ret < 0)
return ret;
meastime = ret;
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)
ret = bu27034_fixp_calc_lx(ch0, ch1, gain0, gain1, meastime, 0);
else if (d1_d0_ratio_scaled < 100)
ret = bu27034_fixp_calc_lx(ch0, ch1, gain0, gain1, meastime, 1);
else
ret = bu27034_fixp_calc_lx(ch0, ch1, gain0, gain1, meastime, 2);
if (ret < 0)
return ret;
*val = ret;
return 0;
}
static int bu27034_get_mlux(struct bu27034_data *data, int chan, int *val)
{
__le16 res[3];
int ret;
ret = bu27034_meas_set(data, true);
if (ret)
return ret;
ret = bu27034_get_result_unlocked(data, &res[0], sizeof(res));
if (ret)
return ret;
ret = bu27034_calc_mlux(data, res, val);
if (ret)
return ret;
ret = bu27034_meas_set(data, false);
if (ret)
dev_err(data->dev, "failed to disable measurement\n");
return 0;
}
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;
*val2 = bu27034_get_int_time(data);
if (*val2 < 0)
return *val2;
return IIO_VAL_INT_PLUS_MICRO;
case IIO_CHAN_INFO_SCALE:
return bu27034_get_scale(data, chan->channel, val, val2);
case IIO_CHAN_INFO_RAW:
{
int (*result_get)(struct bu27034_data *data, int chan, int *val);
if (chan->type == IIO_INTENSITY)
result_get = bu27034_get_single_result;
else if (chan->type == IIO_LIGHT)
result_get = bu27034_get_mlux;
else
return -EINVAL;
/* Don't mess with measurement enabling while buffering */
ret = iio_device_claim_direct_mode(idev);
if (ret)
return ret;
mutex_lock(&data->mutex);
/*
* Reading one channel at a time is inefficient but we
* don't care here. Buffered version should be used if
* performance is an issue.
*/
ret = result_get(data, chan->channel, val);
mutex_unlock(&data->mutex);
iio_device_release_direct_mode(idev);
if (ret)
return ret;
return IIO_VAL_INT;
}
default:
return -EINVAL;
}
}
static int bu27034_write_raw_get_fmt(struct iio_dev *indio_dev,
struct iio_chan_spec const *chan,
long mask)
{
switch (mask) {
case IIO_CHAN_INFO_SCALE:
return IIO_VAL_INT_PLUS_NANO;
case IIO_CHAN_INFO_INT_TIME:
return IIO_VAL_INT_PLUS_MICRO;
default:
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);
int ret;
ret = iio_device_claim_direct_mode(idev);
if (ret)
return ret;
switch (mask) {
case IIO_CHAN_INFO_SCALE:
ret = bu27034_set_scale(data, chan->channel, val, val2);
break;
case IIO_CHAN_INFO_INT_TIME:
if (!val)
ret = bu27034_try_set_int_time(data, val2);
else
ret = -EINVAL;
break;
default:
ret = -EINVAL;
break;
}
iio_device_release_direct_mode(idev);
return ret;
}
static int bu27034_read_avail(struct iio_dev *idev,
struct iio_chan_spec const *chan, const int **vals,
int *type, int *length, long mask)
{
struct bu27034_data *data = iio_priv(idev);
switch (mask) {
case IIO_CHAN_INFO_INT_TIME:
return iio_gts_avail_times(&data->gts, vals, type, length);
case IIO_CHAN_INFO_SCALE:
return iio_gts_all_avail_scales(&data->gts, vals, type, length);
default:
return -EINVAL;
}
}
static const struct iio_info bu27034_info = {
.read_raw = &bu27034_read_raw,
.write_raw = &bu27034_write_raw,
.write_raw_get_fmt = &bu27034_write_raw_get_fmt,
.read_avail = &bu27034_read_avail,
};
static int bu27034_chip_init(struct bu27034_data *data)
{
int ret, sel;
/* Reset */
ret = regmap_write_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");
msleep(1);
ret = regmap_reinit_cache(data->regmap, &bu27034_regmap);
if (ret) {
dev_err(data->dev, "Failed to reinit reg cache\n");
return ret;
}
/*
* Read integration time here to ensure it is in regmap cache. We do
* this to speed-up the int-time acquisition in the start of the buffer
* handling thread where longer delays could make it more likely we end
* up skipping a sample, and where the longer delays make timestamps
* less accurate.
*/
ret = regmap_read(data->regmap, BU27034_REG_MODE_CONTROL1, &sel);
if (ret)
dev_err(data->dev, "reading integration time failed\n");
return 0;
}
static int bu27034_wait_for_data(struct bu27034_data *data)
{
int ret, val;
ret = regmap_read_poll_timeout(data->regmap, BU27034_REG_MODE_CONTROL4,
val, val & BU27034_MASK_VALID,
BU27034_DATA_WAIT_TIME_US,
BU27034_TOTAL_DATA_WAIT_TIME_US);
if (ret) {
dev_err(data->dev, "data polling %s\n",
!(val & BU27034_MASK_VALID) ? "timeout" : "fail");
return ret;
}
ret = regmap_bulk_read(data->regmap, BU27034_REG_DATA0_LO,
&data->scan.channels[0],
sizeof(data->scan.channels));
if (ret)
return ret;
bu27034_invalidate_read_data(data);
return 0;
}
static int bu27034_buffer_thread(void *arg)
{
struct iio_dev *idev = arg;
struct bu27034_data *data;
int wait_ms;
data = iio_priv(idev);
wait_ms = bu27034_get_int_time(data);
wait_ms /= 1000;
wait_ms -= BU27034_MEAS_WAIT_PREMATURE_MS;
while (!kthread_should_stop()) {
int ret;
int64_t tstamp;
msleep(wait_ms);
ret = bu27034_wait_for_data(data);
if (ret)
continue;
tstamp = iio_get_time_ns(idev);
if (test_bit(BU27034_CHAN_ALS, idev->active_scan_mask)) {
int mlux;
ret = bu27034_calc_mlux(data, &data->scan.channels[0],
&mlux);
if (ret)
dev_err(data->dev, "failed to calculate lux\n");
/*
* The maximum Milli lux value we get with gain 1x time
* 55mS data ch0 = 0xffff ch1 = 0xffff fits in 26 bits
* so there should be no problem returning int from
* computations and casting it to u32
*/
data->scan.mlux = (u32)mlux;
}
iio_push_to_buffers_with_timestamp(idev, &data->scan, tstamp);
}
return 0;
}
static int bu27034_buffer_enable(struct iio_dev *idev)
{
struct bu27034_data *data = iio_priv(idev);
struct task_struct *task;
int ret;
mutex_lock(&data->mutex);
ret = bu27034_meas_set(data, true);
if (ret)
goto unlock_out;
task = kthread_run(bu27034_buffer_thread, idev,
"bu27034-buffering-%u",
iio_device_id(idev));
if (IS_ERR(task)) {
ret = PTR_ERR(task);
goto unlock_out;
}
data->task = task;
unlock_out:
mutex_unlock(&data->mutex);
return ret;
}
static int bu27034_buffer_disable(struct iio_dev *idev)
{
struct bu27034_data *data = iio_priv(idev);
int ret;
mutex_lock(&data->mutex);
if (data->task) {
kthread_stop(data->task);
data->task = NULL;
}
ret = bu27034_meas_set(data, false);
mutex_unlock(&data->mutex);
return ret;
}
static const struct iio_buffer_setup_ops bu27034_buffer_ops = {
.postenable = &bu27034_buffer_enable,
.predisable = &bu27034_buffer_disable,
};
static int bu27034_probe(struct i2c_client *i2c)
{
struct device *dev = &i2c->dev;
struct bu27034_data *data;
struct regmap *regmap;
struct iio_dev *idev;
unsigned int part_id, reg;
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");
idev = devm_iio_device_alloc(dev, sizeof(*data));
if (!idev)
return -ENOMEM;
ret = devm_regulator_get_enable(dev, "vdd");
if (ret)
return dev_err_probe(dev, ret, "Failed to get regulator\n");
data = iio_priv(idev);
ret = regmap_read(regmap, BU27034_REG_SYSTEM_CONTROL, &reg);
if (ret)
return dev_err_probe(dev, ret, "Failed to access sensor\n");
part_id = FIELD_GET(BU27034_MASK_PART_ID, reg);
if (part_id != BU27034_ID)
dev_warn(dev, "unknown device 0x%x\n", part_id);
ret = devm_iio_init_iio_gts(dev, 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";
idev->info = &bu27034_info;
idev->modes = INDIO_DIRECT_MODE | INDIO_BUFFER_SOFTWARE;
idev->available_scan_masks = bu27034_scan_masks;
ret = bu27034_chip_init(data);
if (ret)
return ret;
ret = devm_iio_kfifo_buffer_setup(dev, idev, &bu27034_buffer_ops);
if (ret)
return dev_err_probe(dev, ret, "buffer setup failed\n");
ret = devm_iio_device_register(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-als",
.of_match_table = bu27034_of_match,
.probe_type = PROBE_PREFER_ASYNCHRONOUS,
},
.probe = bu27034_probe,
};
module_i2c_driver(bu27034_i2c_driver);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>");
MODULE_DESCRIPTION("ROHM BU27034 ambient light sensor driver");
MODULE_IMPORT_NS(IIO_GTS_HELPER);