On Mon, Jan 09, 2017 at 05:47:37PM +0100, [email protected] wrote:
> From: Jeroen De Wachter <[email protected]>
>
> tmp401 separately read/wrote high and low bytes of temperature values while
> the hardware supports reading/writing those values in one operation. Driver
> has been modified to use word operations where possible.
>
> Tested with a tmp432 sensor on a mips64 platform.
>
> Signed-off-by: Jeroen De Wachter <[email protected]>
> ---
> drivers/hwmon/tmp401.c | 48 +++++++++++++++++++++++++++++-------------------
> 1 file changed, 29 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/hwmon/tmp401.c b/drivers/hwmon/tmp401.c
> index eeeed2c..88b17e4 100644
> --- a/drivers/hwmon/tmp401.c
> +++ b/drivers/hwmon/tmp401.c
> @@ -213,25 +213,29 @@ static int tmp401_update_device_reg16(struct i2c_client
> *client,
> for (i = 0; i < num_sensors; i++) { /* local / r1 / r2 */
> for (j = 0; j < num_regs; j++) { /* temp / low / ... */
> u8 regaddr;
> - /*
> - * High byte must be read first immediately followed
> - * by the low byte
> - */
> +
> regaddr = data->kind == tmp432 ?
> TMP432_TEMP_MSB_READ[j][i] :
> TMP401_TEMP_MSB_READ[j][i];
> - val = i2c_smbus_read_byte_data(client, regaddr);
> - if (val < 0)
> - return val;
> - data->temp[j][i] = val << 8;
> - if (j == 3) /* crit is msb only */
> - continue;
> - regaddr = data->kind == tmp432 ? TMP432_TEMP_LSB[j][i]
> - : TMP401_TEMP_LSB[j][i];
> - val = i2c_smbus_read_byte_data(client, regaddr);
> + if (j == 3) { /* crit is msb only */
> + val = i2c_smbus_read_byte_data(client, regaddr);
> + } else {
> + /*
> + * Hardware provides big endian data. However,
> + * the smbus protocol expects the LSB first in
> + * I2C_SMBUS_WORD_DATA operations.
> + * i2c_smbus_read_word_swapped swaps the bytes
> + * in the value it receives from
> + * i2c_smbus_read_word_data before returning the
> + * data, so we get the correct value.
> + */
Please drop the comment or make it shorter (such as "Hardware provides
big endian data").
> + val = i2c_smbus_read_word_swapped(client,
> + regaddr);
> + }
> if (val < 0)
> return val;
> - data->temp[j][i] |= val;
> +
> + data->temp[j][i] = j == 3 ? val << 8 : val;
> }
> }
> return 0;
> @@ -373,11 +377,17 @@ static ssize_t store_temp(struct device *dev, struct
> device_attribute *devattr,
>
> regaddr = data->kind == tmp432 ? TMP432_TEMP_MSB_WRITE[nr][index]
> : TMP401_TEMP_MSB_WRITE[nr][index];
> - i2c_smbus_write_byte_data(client, regaddr, reg >> 8);
> - if (nr != 3) {
> - regaddr = data->kind == tmp432 ? TMP432_TEMP_LSB[nr][index]
> - : TMP401_TEMP_LSB[nr][index];
> - i2c_smbus_write_byte_data(client, regaddr, reg & 0xFF);
> + if (nr == 3) { /* crit is msb only */
> + i2c_smbus_write_byte_data(client, regaddr, reg >> 8);
> + } else {
> + /*
> + * Hardware expects big endian data. However, the smbus protocol
> + * puts the LSB first in I2C_SMBUS_WORD_DATA operations.
> + * i2c_smbus_write_word_data_swapped will swap the bytes before
> + * passing them to i2c_smbus_write_word_data, so the hardware
> + * will receive the MSB first, as expected.
Comment in one place is enough.
Unless I am missing something, TMP432_TEMP_LSB and TMP401_TEMP_LSB are now
unused and can be removed.
Thanks,
Guenter
> + */
> + i2c_smbus_write_word_swapped(client, regaddr, reg);
> }
> data->temp[nr][index] = reg;
>
> --
> 1.8.3.1
>
