RE: [PATCH v5 6/8] iio: gyro: bmg160: optimize i2c transfers in trigger handler
From: Tirdea, Irina
Date: Mon Aug 17 2015 - 05:34:49 EST
> -----Original Message-----
> From: Jonathan Cameron [mailto:jic23@xxxxxxxxxx]
> Sent: 16 August, 2015 12:25
> To: Tirdea, Irina; Wolfram Sang; linux-iio@xxxxxxxxxxxxxxx; linux-i2c@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx; Pandruvada, Srinivas; Peter Meerwald
> Subject: Re: [PATCH v5 6/8] iio: gyro: bmg160: optimize i2c transfers in trigger handler
>
> On 12/08/15 15:31, Irina Tirdea wrote:
> > 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 bmg160 driver does
> > one i2c transfer for each axis. This has an impact on the frequency
> > of the gyroscope 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: Irina Tirdea <irina.tirdea@xxxxxxxxx>
> > Acked-by: Jonathan Cameron <jic23@xxxxxxxxxx>
> > Acked-by: Srinivas Pandruvada <srinivas.pandruvada@xxxxxxxxxxxxxxx>
> Note, that in the meantime the bmg160 driver just went all regmap
> on us (as part of adding SPI support - though that step hasn't
> happened yet). Hence we'll need a means of telling regmap about this
> possibility.
I think regmap_bulk_read might be enough in my case, but I'll have to
test this. I have also seen there are similar changes for the bmc150 driver,
so I will rebase my changes on top of the regmap ones. That leaves only the
kxcjk-1013 changes to be applied from this patchset.
Thanks,
Irina
>
> > ---
> > drivers/iio/gyro/bmg160.c | 18 ++++++++----------
> > 1 file changed, 8 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/iio/gyro/bmg160.c b/drivers/iio/gyro/bmg160.c
> > index b2a6ccb..1ff306d 100644
> > --- a/drivers/iio/gyro/bmg160.c
> > +++ b/drivers/iio/gyro/bmg160.c
> > @@ -772,6 +772,7 @@ static const struct iio_event_spec bmg160_event = {
> > .sign = 's', \
> > .realbits = 16, \
> > .storagebits = 16, \
> > + .endianness = IIO_LE, \
> > }, \
> > .event_spec = &bmg160_event, \
> > .num_event_specs = 1 \
> > @@ -809,19 +810,16 @@ static irqreturn_t bmg160_trigger_handler(int irq, void *p)
> > struct iio_poll_func *pf = p;
> > struct iio_dev *indio_dev = pf->indio_dev;
> > struct bmg160_data *data = iio_priv(indio_dev);
> > - int bit, ret, i = 0;
> > + int ret = 0;
> >
> > mutex_lock(&data->mutex);
> > - for (bit = 0; bit < AXIS_MAX; bit++) {
> > - ret = i2c_smbus_read_word_data(data->client,
> > - BMG160_AXIS_TO_REG(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,
> > + BMG160_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,
> > pf->timestamp);
> >
--
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