> -----Original Message----- > From: Peter Meerwald [mailto:pmeerw@xxxxxxxxxx] > Sent: 16 February, 2015 21:26 > To: Tirdea, Irina > Cc: Jonathan Cameron; linux-iio@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Pandruvada, Srinivas; Reus, Adriana > Subject: Re: [PATCH 2/2] iio: accel: kxcjk-1013: optimize i2c transfers in trigger handler > > > > Reading all axis values in one i2c transfer reduces the delays > > introduced by the i2c bus. In case i2c block read is not supported, > > fallback to reading each axis as a separate word. > > see comments inline below > Thanks for the review, Peter! > > Signed-off-by: Adriana Reus <adriana.reus@xxxxxxxxx> > > Signed-off-by: Irina Tirdea <irina.tirdea@xxxxxxxxx> > > Reviewed-by: Srinivas Pandruvada <srinivas.pandruvada@xxxxxxxxxxxxxxx> > > --- > > drivers/iio/accel/kxcjk-1013.c | 44 +++++++++++++++++++++++++++++++++--------- > > 1 file changed, 35 insertions(+), 9 deletions(-) > > > > diff --git a/drivers/iio/accel/kxcjk-1013.c b/drivers/iio/accel/kxcjk-1013.c > > index 5f27787..bfa2899 100644 > > --- a/drivers/iio/accel/kxcjk-1013.c > > +++ b/drivers/iio/accel/kxcjk-1013.c > > @@ -109,6 +109,8 @@ struct kxcjk1013_data { > > int64_t timestamp; > > enum kx_chipset chipset; > > bool is_smo8500_device; > > + s32 (*read_block_data)(const struct i2c_client *client, u8 command, > > + u8 length, u8 *values); > > probably this could/should be done in the i2c layer or we end up adding a > similar function in every driver? > Actually this is exactly what I did: adding this code in a couple of drivers :) You are right, this belongs to the i2c core. Will move it there. > > }; > > > > enum kxcjk1013_axis { > > @@ -216,6 +218,23 @@ static const struct { > > {800, 0, 0x06}, > > {1600, 0, 0x06} }; > > > > +static s32 kxcjk1013_read_block_data(const struct i2c_client *client, > > + u8 command, u8 length, u8 *values) > > +{ > > + s32 data; > > + u8 i; > > + > > + for (i = 0; i < length; i += 2) { > > + data = i2c_smbus_read_word_data(client, command + i); > > + if (data < 0) > > + return data; > > + > > + values[i] = data & 0xFF; > > + values[i+1] = data >> 8; > > this is incorrect; it forces the data to be little endian, however, the > endianness (as specified in the driver's .scan_type) is IIO_CPU -- the > code breaks for big-endian CPUs > > since _read_i2c_block_data() can't do endianness conversion (and the chip > does i2c endianness, i.e. little-endian), the .scan_type should become > IIO_LE and above code is correct again but still ugly :) > > bottom line: change .scan_type to IIO_LE > Good point. Changing the endianess to IIO_LE is correct for either kxcjk1013_read_block_data or i2c_smbus_read_i2c_block_data. Will fix this in the next version. Thanks for catching this! > > + } > > + return i; > > +} > > + > > static int kxcjk1013_set_mode(struct kxcjk1013_data *data, > > enum kxcjk1013_mode mode) > > { > > @@ -955,18 +974,14 @@ 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 = data->read_block_data(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); > > @@ -1196,6 +1211,11 @@ static int kxcjk1013_probe(struct i2c_client *client, > > const char *name; > > int ret; > > > > + if (!i2c_check_functionality(client->adapter, > > + I2C_FUNC_SMBUS_BYTE_DATA | > > + I2C_FUNC_SMBUS_READ_WORD_DATA)) > > + return -ENODEV; > > + > > indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data)); > > if (!indio_dev) > > return -ENOMEM; > > @@ -1204,6 +1224,12 @@ static int kxcjk1013_probe(struct i2c_client *client, > > i2c_set_clientdata(client, indio_dev); > > data->client = client; > > > > + if (i2c_check_functionality(client->adapter, > > + I2C_FUNC_SMBUS_READ_I2C_BLOCK)) > > + data->read_block_data = i2c_smbus_read_i2c_block_data; > > + else > > + data->read_block_data = kxcjk1013_read_block_data; > > + > > pdata = dev_get_platdata(&client->dev); > > if (pdata) > > data->active_high_intr = pdata->active_high_intr; > > > > -- > > Peter Meerwald > +43-664-2444418 (mobile) -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
