On 20/02/15 12:02, 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. A good idea. Might be possible to make this a transparent fallback so no special handling is needed in drivers at all (e.g. emulate the block read using the biggest read that is available) - taking care about the endian fun and games that results. Propose it to Wolfram and the i2c list and see what people think of it. Jonathan > >>> }; >>> >>> 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
