Re: [PATCH v2 1/3] iio: magnetometer: ak8975: Fix reading for ak099xx sensors

barnabas.czeman
2024-08-07T15:15:54Z

On 2024-08-06 18:19, Jonathan Cameron wrote:
> On Tue, 06 Aug 2024 08:10:18 +0200
> Barnabás Czémán <barnabas.czeman@mainlining.org> wrote:
>
> Hi Barnabás,
>
> Welcome to IIO.
>
>> ST2 register read should be placed after read measurment data,
>> because it will get correct values after it.
>
> What is the user visible result of this? Do we detect errors when none
> are there? Do we have a datasheet reference for the status being
> update on the read command, not after the trigger?
>>
> Needs a Fixes tag to let us know how far to backport the fix.
>
> A few comments inline.
>
>> Signed-off-by: Barnabás Czémán <barnabas.czeman@mainlining.org>
>> ---
>> drivers/iio/magnetometer/ak8975.c | 31
>> +++++++++++++++----------------
>> 1 file changed, 15 insertions(+), 16 deletions(-)
>>
>> diff --git a/drivers/iio/magnetometer/ak8975.c
>> b/drivers/iio/magnetometer/ak8975.c
>> index dd466c5fa621..925d76062b3e 100644
>> --- a/drivers/iio/magnetometer/ak8975.c
>> +++ b/drivers/iio/magnetometer/ak8975.c
>> @@ -692,22 +692,7 @@ static int ak8975_start_read_axis(struct
>> ak8975_data *data,
>> if (ret < 0)
>> return ret;
>>
>> - /* This will be executed only for non-interrupt based waiting case
>> */
>> - if (ret & data->def->ctrl_masks[ST1_DRDY]) {
>> - ret = i2c_smbus_read_byte_data(client,
>> - data->def->ctrl_regs[ST2]);
>> - if (ret < 0) {
>> - dev_err(&client->dev, "Error in reading ST2\n");
>> - return ret;
>> - }
>> - if (ret & (data->def->ctrl_masks[ST2_DERR] |
>> - data->def->ctrl_masks[ST2_HOFL])) {
>> - dev_err(&client->dev, "ST2 status error 0x%x\n", ret);
>> - return -EINVAL;
>> - }
>> - }
>> -
> This completely removes the check from the _fill_buffer() path
>
>> - return 0;
>> + return !(ret & data->def->ctrl_masks[ST1_DRDY]);
> returning a positive value here is unusual enough you should add a
> comment for
> the function + use that return value.
>
>> }
>>
>> /* Retrieve raw flux value for one of the x, y, or z axis. */
>> @@ -731,6 +716,20 @@ static int ak8975_read_axis(struct iio_dev
>> *indio_dev, int index, int *val)
>> ret = i2c_smbus_read_i2c_block_data_or_emulated(
>> client, def->data_regs[index],
>> sizeof(rval), (u8*)&rval);
> No longer gated on ret & data->def->ctrl_masks[ST1_DRDY] which seems
> unintentional.
It is checked exactly before the measurement data read, it is the return
value of ak8975_start_read_axis.
The read section should be ST1 -> measurement -> ST2, exactly the same
can be found in the datasheets.
>
> Still need a check on ret here.
>
>> + ret = i2c_smbus_read_byte_data(client,
>> + data->def->ctrl_regs[ST2]);
>> + if (ret < 0) {
>> + dev_err(&client->dev, "Error in reading ST2\n");
>> + goto exit;
>> + }
>> +
>> + if (ret & (data->def->ctrl_masks[ST2_DERR] |
>> + data->def->ctrl_masks[ST2_HOFL])) {
>> + dev_err(&client->dev, "ST2 status error 0x%x\n", ret);
>> + ret = -EINVAL;
>> + goto exit;
>> + }
>> +
>> if (ret < 0)
>> goto exit;
>
> And this one ends up redundant I think which suggests to me the
> code is inserted a few lines early.
>
>>
>>