iio: mma8452: add support for oversampling ratio

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@posteo.de>
Signed-off-by: Christoph Muellner <christoph.muellner@theobroma-systems.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

1 files changed, 160 insertions, 25 deletions

diff --git a/drivers/iio/accel/mma8452.c b/drivers/iio/accel/mma8452.c
index e225d3c53bd5..458c82715427 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
 };