Am 15.02.2017 um 00:03 schrieb Martin Blumenstingl:
> On Tue, Feb 14, 2017 at 10:58 PM, Heiner Kallweit <hkallweit1@xxxxxxxxx> wrote:
>> After sampling there should always be only one value in the FIFO.
>> This also applies to averaging mode as the averaging is done
>> chip-internally. So we don't have to loop and let the driver
>> complain if there's not exactly one value in the FIFO.
>>
>> If the value belongs to a different channel then don't silently
>> swallow the value but complain.
>>
>> Signed-off-by: Heiner Kallweit <hkallweit1@xxxxxxxxx>
> Acked-by: Martin Blumenstingl <martin.blumenstingl@xxxxxxxxxxxxxx>
>
>> ---
>> drivers/iio/adc/meson_saradc.c | 36 +++++++++++++++++-------------------
>> 1 file changed, 17 insertions(+), 19 deletions(-)
>>
>> diff --git a/drivers/iio/adc/meson_saradc.c b/drivers/iio/adc/meson_saradc.c
>> index dbd56bcc..d39711c0 100644
>> --- a/drivers/iio/adc/meson_saradc.c
>> +++ b/drivers/iio/adc/meson_saradc.c
>> @@ -278,33 +278,31 @@ static int meson_sar_adc_read_raw_sample(struct iio_dev *indio_dev,
>> int *val)
>> {
>> struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
>> - int regval, fifo_chan, fifo_val, sum = 0, count = 0;
>> + int regval, fifo_chan, fifo_val, count;
>>
>> if(!wait_for_completion_timeout(&priv->done,
>> msecs_to_jiffies(MESON_SAR_ADC_TIMEOUT)))
>> return -ETIMEDOUT;
>>
>
> I thought I had changed the following loop when I introduced
> meson_sar_adc_clear_fifo() but it seems that I didn't do it - so
> thanks for cleaning this up!
>> - while (meson_sar_adc_get_fifo_count(indio_dev) > 0 &&
>> - count < MESON_SAR_ADC_MAX_FIFO_SIZE) {
>> - regmap_read(priv->regmap, MESON_SAR_ADC_FIFO_RD, ®val);
>> -
>> - fifo_chan = FIELD_GET(MESON_SAR_ADC_FIFO_RD_CHAN_ID_MASK,
>> - regval);
>> - if (fifo_chan != chan->channel)
>> - continue;
>> -
>> - fifo_val = FIELD_GET(MESON_SAR_ADC_FIFO_RD_SAMPLE_VALUE_MASK,
>> - regval);
>> - fifo_val &= (BIT(priv->data->resolution) - 1);
>> -
>> - sum += fifo_val;
>> - count++;
>> + count = meson_sar_adc_get_fifo_count(indio_dev);
>> + if (count != 1) {
>> + dev_err(&indio_dev->dev,
>> + "ADC FIFO has %d elements instead of one\n", count);
>> + return -EINVAL;
>> }
>>
>> - if (!count)
>> - return -ENOENT;
>> + regmap_read(priv->regmap, MESON_SAR_ADC_FIFO_RD, ®val);
>> + fifo_chan = FIELD_GET(MESON_SAR_ADC_FIFO_RD_CHAN_ID_MASK, regval);
>> + if (fifo_chan != chan->channel) {
>> + dev_err(&indio_dev->dev,
>> + "ADC FIFO entry belongs to channel %d instead of %d\n",
>> + fifo_chan, chan->channel);
>> + return -EINVAL;
>> + }
>>
>> - *val = sum / count;
>> + fifo_val = FIELD_GET(MESON_SAR_ADC_FIFO_RD_SAMPLE_VALUE_MASK, regval);
>> + fifo_val &= GENMASK(priv->data->resolution - 1, 0);
> my code used "BIT(priv->data->resolution) - 1" instead of GENMASK. it
> shouldn't make a difference so I don't see an issue with that change
>
Functionally it's the same. I just think that using GENMASK is more
intuitive here as the statement is about applying a bitmask to a value.
>> + *val = fifo_val;
>>
>> return 0;
>> }
>> --
>> 2.11.1
>>
>>
>
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