On Fri, 2015-02-20 at 12:02 +0000, Tirdea, Irina wrote: > > > -----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! > I don't think changing to IIO_LE is good idea as when i2c_read_bock.. then the scan type will be CPU. So better to fix endianness in this function. > > > + } > > > + 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) ��.n��������+%������w��{.n�����{��(��)�� jg��� �����ݢj����G���� ���j:+v���w�m������w�������h�����٥
