On 19/04/16 10:18, Gregor Boirie wrote:
> Triggered buffering memory accesses are not aligned on per channel
> storagebits boundaries. Fix this by reading each channel individually to
> ensure proper alignment.
> Note that this patch drops the earlier optimisation that packs multiple
> channels reading into a single data block transaction when their
> respective I2C register addresses are contiguous.
I wonder how much effect this change has on the read out rate and whether
repacking in software would be significantly quicker than the multiple
transfers...
>
> Signed-off-by: Gregor Boirie <gregor.boirie@xxxxxxxxxx>
> ---
> drivers/iio/common/st_sensors/st_sensors_buffer.c | 38 ++++++++++-------------
> drivers/iio/common/st_sensors/st_sensors_core.c | 2 +-
> 2 files changed, 18 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/iio/common/st_sensors/st_sensors_buffer.c b/drivers/iio/common/st_sensors/st_sensors_buffer.c
> index c558985..a7f1ced 100644
> --- a/drivers/iio/common/st_sensors/st_sensors_buffer.c
> +++ b/drivers/iio/common/st_sensors/st_sensors_buffer.c
> @@ -21,33 +21,29 @@
>
> #include <linux/iio/common/st_sensors.h>
>
> -
> int st_sensors_get_buffer_element(struct iio_dev *indio_dev, u8 *buf)
> {
> - int i, len;
> - int total = 0;
> + unsigned int cid;
> struct st_sensor_data *sdata = iio_priv(indio_dev);
> - unsigned int num_data_channels = sdata->num_data_channels;
> -
> - for (i = 0; i < num_data_channels; i++) {
> - unsigned int bytes_to_read;
> -
> - if (test_bit(i, indio_dev->active_scan_mask)) {
> - bytes_to_read = indio_dev->channels[i].scan_type.storagebits >> 3;
> - len = sdata->tf->read_multiple_byte(&sdata->tb,
> - sdata->dev, indio_dev->channels[i].address,
> - bytes_to_read,
> - buf + total, sdata->multiread_bit);
> -
> - if (len < bytes_to_read)
> - return -EIO;
>
> - /* Advance the buffer pointer */
> - total += len;
> - }
> + for_each_set_bit(cid, indio_dev->active_scan_mask,
> + sdata->num_data_channels) {
> + const struct iio_chan_spec *chan = &indio_dev->channels[cid];
> + int sb = chan->scan_type.storagebits / 8;
> + int rb = chan->scan_type.realbits / 8;
> + int err;
> +
> + buf = PTR_ALIGN(buf, sb);
> + err = sdata->tf->read_multiple_byte(&sdata->tb, sdata->dev,
> + chan->address, rb, buf,
> + sdata->multiread_bit);
> + if (err != rb)
> + return (err < 0) ? err : -EIO;
> +
> + buf += sb;
> }
>
> - return total;
> + return 0;
> }
> EXPORT_SYMBOL(st_sensors_get_buffer_element);
>
> diff --git a/drivers/iio/common/st_sensors/st_sensors_core.c b/drivers/iio/common/st_sensors/st_sensors_core.c
> index dffe006..6901c7f 100644
> --- a/drivers/iio/common/st_sensors/st_sensors_core.c
> +++ b/drivers/iio/common/st_sensors/st_sensors_core.c
> @@ -463,7 +463,7 @@ static int st_sensors_read_axis_data(struct iio_dev *indio_dev,
> int err;
> u8 *outdata;
> struct st_sensor_data *sdata = iio_priv(indio_dev);
> - unsigned int byte_for_channel = ch->scan_type.storagebits >> 3;
> + unsigned int byte_for_channel = ch->scan_type.realbits >> 3;
>
> outdata = kmalloc(byte_for_channel, GFP_KERNEL);
> if (!outdata)
>
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