On 15/05/2018 21:08, Martin Kelly wrote:
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On 05/14/2018 02:05 PM, Jean-Baptiste Maneyrol wrote:
Instead of storing fifo rate in Hz, store the chip internal sample
rate divider. This will be more useful for timestamping. There
are both equivalent.
Signed-off-by: Jean-Baptiste Maneyrol <jmaneyrol@xxxxxxxxxxxxxx>
---
drivers/iio/imu/inv_mpu6050/inv_mpu_core.c | 15 +++++++++------
drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h | 4 ++--
2 files changed, 11 insertions(+), 8 deletions(-)
diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c
b/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c
index 1e7e750..9e5c5e7 100644
--- a/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c
+++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c
@@ -82,7 +82,7 @@ static const struct inv_mpu6050_reg_map reg_set_6050
= {
static const struct inv_mpu6050_chip_config chip_config_6050 = {
.fsr = INV_MPU6050_FSR_2000DPS,
.lpf = INV_MPU6050_FILTER_20HZ,
- .fifo_rate = INV_MPU6050_INIT_FIFO_RATE,
+ .divider = (INV_MPU6050_ONE_K_HZ / INV_MPU6050_INIT_FIFO_RATE) - 1,
.gyro_fifo_enable = false,
.accl_fifo_enable = false,
.accl_fs = INV_MPU6050_FS_02G,
@@ -628,7 +628,7 @@ static ssize_t
inv_mpu6050_fifo_rate_store(struct device *dev, struct
device_attribute *attr,
const char *buf, size_t count)
{
- s32 fifo_rate;
+ int fifo_rate;
u8 d;
Since the divider is a u8, I think the fifo_rate should also be unsigned
(I think u8 would fit it, but unsigned int should be fine too).
fifo_rate is taken from sysfs entry using kstrtoint which requires a
signed int. The user can enter any number, even negative ones. Using a
signed integer for reading the entry enables to catch negative number
and return EINVAL for them.
int result;
struct iio_dev *indio_dev = dev_to_iio_dev(dev);
@@ -644,8 +644,12 @@ inv_mpu6050_fifo_rate_store(struct device *dev,
struct device_attribute *attr,
if (result)
return result;
+ /* compute freq divider and update fifo rate in case of
truncation */
+ d = INV_MPU6050_ONE_K_HZ / fifo_rate - 1;
+ fifo_rate = INV_MPU6050_ONE_K_HZ / (d + 1);
+
I don't quite understand why we need to set fifo_rate again. Could you
explain?
Since fifo_rate is an arbitrary number coming from userspace, it can be
a rate that is not supported by the chip (not a divider of 1KHz). For
dealing with this case, I compute first the divider using provided
value. This computation will return a truncated number that is not
providing necessary the fifo rate asked if it is not supported. So I
compute back the fifo rate using this divider to store the real value.
mutex_lock(&st->lock);
- if (fifo_rate == st->chip_config.fifo_rate) {
+ if (d == st->chip_config.divider) {
result = 0;
goto fifo_rate_fail_unlock;
}
@@ -653,11 +657,10 @@ inv_mpu6050_fifo_rate_store(struct device *dev,
struct device_attribute *attr,
if (result)
goto fifo_rate_fail_unlock;
- d = INV_MPU6050_ONE_K_HZ / fifo_rate - 1;
result = regmap_write(st->map, st->reg->sample_rate_div, d);
if (result)
goto fifo_rate_fail_power_off;
- st->chip_config.fifo_rate = fifo_rate;
+ st->chip_config.divider = d;
result = inv_mpu6050_set_lpf(st, fifo_rate);
if (result)
@@ -685,7 +688,7 @@ inv_fifo_rate_show(struct device *dev, struct
device_attribute *attr,
unsigned fifo_rate;
mutex_lock(&st->lock);
- fifo_rate = st->chip_config.fifo_rate;
+ fifo_rate = INV_MPU6050_ONE_K_HZ / (st->chip_config.divider + 1);
Since we use this same line twice, I think it would be useful to put it
in a function inv_calculate_fifo_rate(u8 divider) or similar.
That is indeed possible.
mutex_unlock(&st->lock);
return scnprintf(buf, PAGE_SIZE, "%u\n", fifo_rate);
diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h
b/drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h
index a92ddd4..8d9044c 100644
--- a/drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h
+++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_iio.h
@@ -86,7 +86,7 @@ enum inv_devices {
* @accl_fs: accel full scale range.
* @accl_fifo_enable: enable accel data output
* @gyro_fifo_enable: enable gyro data output
- * @fifo_rate: FIFO update rate.
+ * @divider: sample rate divider.
*/
struct inv_mpu6050_chip_config {
unsigned int fsr:2;
@@ -94,7 +94,7 @@ struct inv_mpu6050_chip_config {
unsigned int accl_fs:2;
unsigned int accl_fifo_enable:1;
unsigned int gyro_fifo_enable:1;
- u16 fifo_rate;
+ u8 divider;
u8 user_ctrl;
};
--
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