From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jonathan Cameron Subject: Re: [PATCH v3 8/8] iio: accel: kxcjk-1013: optimize i2c transfers in trigger handler Date: Sun, 05 Jul 2015 13:11:04 +0100 Message-ID: <55991ED8.5020500@kernel.org> References: <1435916017-12859-1-git-send-email-irina.tirdea@intel.com> <1435916017-12859-9-git-send-email-irina.tirdea@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1435916017-12859-9-git-send-email-irina.tirdea-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Irina Tirdea , Wolfram Sang , linux-iio-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Srinivas Pandruvada , Peter Meerwald , Adriana Reus List-Id: linux-i2c@vger.kernel.org On 03/07/15 10:33, Irina Tirdea wrote: > From: Adriana Reus > > 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 > Signed-off-by: Irina Tirdea Same comments as previously. Acked-by: Jonathan Cameron > --- > 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); >