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SubjectRe: [PATCH v3 8/8] iio: accel: kxcjk-1013: optimize i2c transfers in trigger handler
On 03/07/15 10:33, Irina Tirdea wrote:
> From: Adriana Reus <adriana.reus@intel.com>
>
> Some i2c busses (e.g.: Synopsys DesignWare I2C adapter) need to
> enable/disable the bus at each i2c transfer and must wait for
> the enable/disable to happen before sending the data.
>
> When reading data in the trigger handler, the kxcjk-1013 accel driver
> does one i2c transfer for each axis. This has an impact on the
> frequency of the accelerometer at high sample rates due to additional
> delays introduced by the i2c bus at each transfer.
>
> Reading all axis values in one i2c transfer reduces the delays
> introduced by the i2c bus. Uses i2c_smbus_read_i2c_block_data_or_emulated
> that will fallback to reading each axis as a separate word in case i2c
> block read is not supported.
>
> Signed-off-by: Adriana Reus <adriana.reus@intel.com>
> Signed-off-by: Irina Tirdea <irina.tirdea@intel.com>
Same comments as previously.

Acked-by: Jonathan Cameron <jic23@kernel.org>
> ---
> drivers/iio/accel/kxcjk-1013.c | 19 ++++++++-----------
> 1 file changed, 8 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/iio/accel/kxcjk-1013.c b/drivers/iio/accel/kxcjk-1013.c
> index 4960397..8f401c2 100644
> --- a/drivers/iio/accel/kxcjk-1013.c
> +++ b/drivers/iio/accel/kxcjk-1013.c
> @@ -923,7 +923,7 @@ static const struct iio_event_spec kxcjk1013_event = {
> .realbits = 12, \
> .storagebits = 16, \
> .shift = 4, \
> - .endianness = IIO_CPU, \
> + .endianness = IIO_LE, \
> }, \
> .event_spec = &kxcjk1013_event, \
> .num_event_specs = 1 \
> @@ -955,19 +955,16 @@ static irqreturn_t kxcjk1013_trigger_handler(int irq, void *p)
> struct iio_poll_func *pf = p;
> struct iio_dev *indio_dev = pf->indio_dev;
> struct kxcjk1013_data *data = iio_priv(indio_dev);
> - int bit, ret, i = 0;
> + int ret;
>
> mutex_lock(&data->mutex);
> -
> - for (bit = 0; bit < AXIS_MAX; bit++) {
> - ret = kxcjk1013_get_acc_reg(data, bit);
> - if (ret < 0) {
> - mutex_unlock(&data->mutex);
> - goto err;
> - }
> - data->buffer[i++] = ret;
> - }
> + ret = i2c_smbus_read_i2c_block_data_or_emulated(data->client,
> + KXCJK1013_REG_XOUT_L,
> + AXIS_MAX * 2,
> + (u8 *)data->buffer);
> mutex_unlock(&data->mutex);
> + if (ret < 0)
> + goto err;
>
> iio_push_to_buffers_with_timestamp(indio_dev, data->buffer,
> data->timestamp);
>



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