[PATCH] iio: mma8452: add support for oversampling ratio

From: Martin Kepplinger
Date: Mon Apr 25 2016 - 08:10:23 EST

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This adds the following sysfs files according to the iio ABI:

-rw-r--r-- 4096 in_accel_oversampling_ratio
-r--r--r-- 4096 in_accel_oversampling_ratio_available

Internally, the device knows about 4 different power modes that differ
in oversampling ratio (and power consumption). We just show the user
what oversampling ratio(s) is/are available, depending on the current
frequency.

The referenced table in the datasheets makes it easier to understand.

Signed-off-by: Martin Kepplinger <martink@xxxxxxxxx>
Signed-off-by: Christoph Muellner <christoph.muellner@xxxxxxxxxxxxxxxxxxxxx>
---
This is meant to get merged for v4.8 to have time for review and possibly
testing by others.

thanks,
martin

drivers/iio/accel/mma8452.c | 185 ++++++++++++++++++++++++++++++++++++++------
1 file changed, 160 insertions(+), 25 deletions(-)

diff --git a/drivers/iio/accel/mma8452.c b/drivers/iio/accel/mma8452.c
index e225d3c..458c827 100644
--- a/drivers/iio/accel/mma8452.c
+++ b/drivers/iio/accel/mma8452.c
@@ -76,6 +76,8 @@
#define MMA8452_CTRL_DR_DEFAULT 0x4 /* 50 Hz sample frequency */
#define MMA8452_CTRL_REG2 0x2b
#define MMA8452_CTRL_REG2_RST BIT(6)
+#define MMA8452_CTRL_REG2_MODS_SHIFT 3
+#define MMA8452_CTRL_REG2_MODS_MASK 0x1b
#define MMA8452_CTRL_REG4 0x2d
#define MMA8452_CTRL_REG5 0x2e
#define MMA8452_OFF_X 0x2f
@@ -257,20 +259,17 @@ static const int mma8452_samp_freq[8][2] = {
{6, 250000}, {1, 560000}
};

-/* Datasheet table 35 (step time vs sample frequency) */
-static const int mma8452_transient_time_step_us[8] = {
- 1250,
- 2500,
- 5000,
- 10000,
- 20000,
- 20000,
- 20000,
- 20000
+/* Datasheet table: step time "Relationship with the ODR" (sample frequency) */
+static const int mma8452_transient_time_step_us[4][8] = {
+ { 1250, 2500, 5000, 10000, 20000, 20000, 20000, 20000 }, /* normal */
+ { 1250, 2500, 5000, 10000, 20000, 80000, 80000, 80000 }, /* l p l n */
+ { 1250, 2500, 2500, 2500, 2500, 2500, 2500, 2500 }, /* high res*/
+ { 1250, 2500, 5000, 10000, 20000, 80000, 160000, 160000 } /* l p */
};

-/* Datasheet table 18 (normal mode) */
-static const int mma8452_hp_filter_cutoff[8][4][2] = {
+/* Datasheet table "High-Pass Filter Cutoff Options" */
+static const int mma8452_hp_filter_cutoff[4][8][4][2] = {
+ { /* normal */
{ {16, 0}, {8, 0}, {4, 0}, {2, 0} }, /* 800 Hz sample */
{ {16, 0}, {8, 0}, {4, 0}, {2, 0} }, /* 400 Hz sample */
{ {8, 0}, {4, 0}, {2, 0}, {1, 0} }, /* 200 Hz sample */
@@ -279,8 +278,61 @@ static const int mma8452_hp_filter_cutoff[8][4][2] = {
{ {2, 0}, {1, 0}, {0, 500000}, {0, 250000} }, /* 12.5 Hz sample */
{ {2, 0}, {1, 0}, {0, 500000}, {0, 250000} }, /* 6.25 Hz sample */
{ {2, 0}, {1, 0}, {0, 500000}, {0, 250000} } /* 1.56 Hz sample */
+ },
+ { /* low noise low power */
+ { {16, 0}, {8, 0}, {4, 0}, {2, 0} },
+ { {16, 0}, {8, 0}, {4, 0}, {2, 0} },
+ { {8, 0}, {4, 0}, {2, 0}, {1, 0} },
+ { {4, 0}, {2, 0}, {1, 0}, {0, 500000} },
+ { {2, 0}, {1, 0}, {0, 500000}, {0, 250000} },
+ { {0, 500000}, {0, 250000}, {0, 125000}, {0, 063000} },
+ { {0, 500000}, {0, 250000}, {0, 125000}, {0, 063000} },
+ { {0, 500000}, {0, 250000}, {0, 125000}, {0, 063000} }
+ },
+ { /* high resolution */
+ { {16, 0}, {8, 0}, {4, 0}, {2, 0} },
+ { {16, 0}, {8, 0}, {4, 0}, {2, 0} },
+ { {16, 0}, {8, 0}, {4, 0}, {2, 0} },
+ { {16, 0}, {8, 0}, {4, 0}, {2, 0} },
+ { {16, 0}, {8, 0}, {4, 0}, {2, 0} },
+ { {16, 0}, {8, 0}, {4, 0}, {2, 0} },
+ { {16, 0}, {8, 0}, {4, 0}, {2, 0} },
+ { {16, 0}, {8, 0}, {4, 0}, {2, 0} }
+ },
+ { /* low power */
+ { {16, 0}, {8, 0}, {4, 0}, {2, 0} },
+ { {8, 0}, {4, 0}, {2, 0}, {1, 0} },
+ { {4, 0}, {2, 0}, {1, 0}, {0, 500000} },
+ { {2, 0}, {1, 0}, {0, 500000}, {0, 250000} },
+ { {1, 0}, {0, 500000}, {0, 250000}, {0, 125000} },
+ { {0, 250000}, {0, 125000}, {0, 063000}, {0, 031000} },
+ { {0, 250000}, {0, 125000}, {0, 063000}, {0, 031000} },
+ { {0, 250000}, {0, 125000}, {0, 063000}, {0, 031000} }
+ }
};

+/* Datasheet table "MODS Oversampling modes averaging values at each ODR" */
+static const u16 mma8452_os_ratio[4][8] = {
+ /* 800 Hz, 400 Hz, ... , 1.56 Hz */
+ { 2, 4, 4, 4, 4, 16, 32, 128 }, /* normal */
+ { 2, 4, 4, 4, 4, 4, 8, 32 }, /* low power low noise */
+ { 2, 4, 8, 16, 32, 128, 256, 1024 }, /* high resolution */
+ { 2, 2, 2, 2, 2, 2, 4, 16 } /* low power */
+};
+
+static int mma8452_get_power_mode(struct mma8452_data *data)
+{
+ int reg;
+
+ reg = i2c_smbus_read_byte_data(data->client,
+ MMA8452_CTRL_REG2);
+ if (reg < 0)
+ return reg;
+
+ return ((reg & MMA8452_CTRL_REG2_MODS_MASK) >>
+ MMA8452_CTRL_REG2_MODS_SHIFT);
+}
+
static ssize_t mma8452_show_samp_freq_avail(struct device *dev,
struct device_attribute *attr,
char *buf)
@@ -306,10 +358,39 @@ static ssize_t mma8452_show_hp_cutoff_avail(struct device *dev,
{
struct iio_dev *indio_dev = dev_to_iio_dev(dev);
struct mma8452_data *data = iio_priv(indio_dev);
+ int i, j;
+
+ i = mma8452_get_odr_index(data);
+ j = mma8452_get_power_mode(data);
+ if (j < 0)
+ return j;
+
+ return mma8452_show_int_plus_micros(buf, mma8452_hp_filter_cutoff[j][i],
+ ARRAY_SIZE(mma8452_hp_filter_cutoff[0][0]));
+}
+
+static ssize_t mma8452_show_os_ratio_avail(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct iio_dev *indio_dev = dev_to_iio_dev(dev);
+ struct mma8452_data *data = iio_priv(indio_dev);
int i = mma8452_get_odr_index(data);
+ int j;
+ u16 val = 0;
+ size_t len = 0;
+
+ for (j = 0; j < ARRAY_SIZE(mma8452_os_ratio); j++) {
+ if (val == mma8452_os_ratio[j][i])
+ continue;
+
+ val = mma8452_os_ratio[j][i];
+
+ len += scnprintf(buf + len, PAGE_SIZE - len, "%d ", val);
+ }
+ buf[len - 1] = '\n';

- return mma8452_show_int_plus_micros(buf, mma8452_hp_filter_cutoff[i],
- ARRAY_SIZE(mma8452_hp_filter_cutoff[0]));
+ return len;
}

static IIO_DEV_ATTR_SAMP_FREQ_AVAIL(mma8452_show_samp_freq_avail);
@@ -317,6 +398,8 @@ static IIO_DEVICE_ATTR(in_accel_scale_available, S_IRUGO,
mma8452_show_scale_avail, NULL, 0);
static IIO_DEVICE_ATTR(in_accel_filter_high_pass_3db_frequency_available,
S_IRUGO, mma8452_show_hp_cutoff_avail, NULL, 0);
+static IIO_DEVICE_ATTR(in_accel_oversampling_ratio_available, S_IRUGO,
+ mma8452_show_os_ratio_avail, NULL, 0);

static int mma8452_get_samp_freq_index(struct mma8452_data *data,
int val, int val2)
@@ -335,24 +418,33 @@ static int mma8452_get_scale_index(struct mma8452_data *data, int val, int val2)
static int mma8452_get_hp_filter_index(struct mma8452_data *data,
int val, int val2)
{
- int i = mma8452_get_odr_index(data);
+ int i, j;
+
+ i = mma8452_get_odr_index(data);
+ j = mma8452_get_power_mode(data);
+ if (j < 0)
+ return j;

- return mma8452_get_int_plus_micros_index(mma8452_hp_filter_cutoff[i],
- ARRAY_SIZE(mma8452_hp_filter_cutoff[0]), val, val2);
+ return mma8452_get_int_plus_micros_index(mma8452_hp_filter_cutoff[j][i],
+ ARRAY_SIZE(mma8452_hp_filter_cutoff[0][0]), val, val2);
}

static int mma8452_read_hp_filter(struct mma8452_data *data, int *hz, int *uHz)
{
- int i, ret;
+ int j, i, ret;

ret = i2c_smbus_read_byte_data(data->client, MMA8452_HP_FILTER_CUTOFF);
if (ret < 0)
return ret;

i = mma8452_get_odr_index(data);
+ j = mma8452_get_power_mode(data);
+ if (j < 0)
+ return j;
+
ret &= MMA8452_HP_FILTER_CUTOFF_SEL_MASK;
- *hz = mma8452_hp_filter_cutoff[i][ret][0];
- *uHz = mma8452_hp_filter_cutoff[i][ret][1];
+ *hz = mma8452_hp_filter_cutoff[j][i][ret][0];
+ *uHz = mma8452_hp_filter_cutoff[j][i][ret][1];

return 0;
}
@@ -414,6 +506,15 @@ static int mma8452_read_raw(struct iio_dev *indio_dev,
}

return IIO_VAL_INT_PLUS_MICRO;
+ case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
+ ret = mma8452_get_power_mode(data);
+ if (ret < 0)
+ return ret;
+
+ i = mma8452_get_odr_index(data);
+
+ *val = mma8452_os_ratio[ret][i];
+ return IIO_VAL_INT;
}

return -EINVAL;
@@ -480,6 +581,21 @@ fail:
return ret;
}

+static int mma8452_set_power_mode(struct mma8452_data *data, u8 mode)
+{
+ int reg;
+
+ reg = i2c_smbus_read_byte_data(data->client,
+ MMA8452_CTRL_REG2);
+ if (reg < 0)
+ return reg;
+
+ reg &= ~MMA8452_CTRL_REG2_MODS_MASK;
+ reg |= mode << MMA8452_CTRL_REG2_MODS_SHIFT;
+
+ return mma8452_change_config(data, MMA8452_CTRL_REG2, reg);
+}
+
/* returns >0 if in freefall mode, 0 if not or <0 if an error occurred */
static int mma8452_freefall_mode_enabled(struct mma8452_data *data)
{
@@ -597,6 +713,14 @@ static int mma8452_write_raw(struct iio_dev *indio_dev,
return mma8452_change_config(data, MMA8452_DATA_CFG,
data->data_cfg);

+ case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
+ ret = mma8452_get_odr_index(data);
+
+ for (i = 0; i < ARRAY_SIZE(mma8452_os_ratio); i++) {
+ if (mma8452_os_ratio[i][ret] == val)
+ return mma8452_set_power_mode(data, i);
+ }
+
default:
return -EINVAL;
}
@@ -610,7 +734,7 @@ static int mma8452_read_thresh(struct iio_dev *indio_dev,
int *val, int *val2)
{
struct mma8452_data *data = iio_priv(indio_dev);
- int ret, us;
+ int ret, us, power_mode;

switch (info) {
case IIO_EV_INFO_VALUE:
@@ -629,7 +753,11 @@ static int mma8452_read_thresh(struct iio_dev *indio_dev,
if (ret < 0)
return ret;

- us = ret * mma8452_transient_time_step_us[
+ power_mode = mma8452_get_power_mode(data);
+ if (power_mode < 0)
+ return power_mode;
+
+ us = ret * mma8452_transient_time_step_us[power_mode][
mma8452_get_odr_index(data)];
*val = us / USEC_PER_SEC;
*val2 = us % USEC_PER_SEC;
@@ -677,8 +805,12 @@ static int mma8452_write_thresh(struct iio_dev *indio_dev,
val);

case IIO_EV_INFO_PERIOD:
+ ret = mma8452_get_power_mode(data);
+ if (ret < 0)
+ return ret;
+
steps = (val * USEC_PER_SEC + val2) /
- mma8452_transient_time_step_us[
+ mma8452_transient_time_step_us[ret][
mma8452_get_odr_index(data)];

if (steps < 0 || steps > 0xff)
@@ -978,7 +1110,8 @@ static struct attribute_group mma8452_event_attribute_group = {
BIT(IIO_CHAN_INFO_CALIBBIAS), \
.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SAMP_FREQ) | \
BIT(IIO_CHAN_INFO_SCALE) | \
- BIT(IIO_CHAN_INFO_HIGH_PASS_FILTER_3DB_FREQUENCY), \
+ BIT(IIO_CHAN_INFO_HIGH_PASS_FILTER_3DB_FREQUENCY) | \
+ BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO), \
.scan_index = idx, \
.scan_type = { \
.sign = 's', \
@@ -998,7 +1131,8 @@ static struct attribute_group mma8452_event_attribute_group = {
.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | \
BIT(IIO_CHAN_INFO_CALIBBIAS), \
.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SAMP_FREQ) | \
- BIT(IIO_CHAN_INFO_SCALE), \
+ BIT(IIO_CHAN_INFO_SCALE) | \
+ BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO), \
.scan_index = idx, \
.scan_type = { \
.sign = 's', \
@@ -1171,6 +1305,7 @@ static struct attribute *mma8452_attributes[] = {
&iio_dev_attr_sampling_frequency_available.dev_attr.attr,
&iio_dev_attr_in_accel_scale_available.dev_attr.attr,
&iio_dev_attr_in_accel_filter_high_pass_3db_frequency_available.dev_attr.attr,
+ &iio_dev_attr_in_accel_oversampling_ratio_available.dev_attr.attr,
NULL
};

--
2.1.4

Next message: Mikko Rapeli: "Re: [PATCH v2] uapi glibc compat: fix compile errors when glibc net/if.h included before linux/if.h"
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