linux-kernel - Re: [PATCH] iio: palmas: shut up warning about calibration mismatch (due to noise)

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Message-Id: <18533164-C17A-4CA1-A882-5A160D370498@goldelico.com>
Date:   Sun, 20 Mar 2022 17:28:21 +0100
From:   "H. Nikolaus Schaller" <hns@...delico.com>
To:     Jonathan Cameron <jic23@...nel.org>
Cc:     Colin Ian King <colin.king@...el.com>,
        Sergiu Cuciurean <sergiu.cuciurean@...log.com>,
        Julia Lawall <Julia.Lawall@...ia.fr>,
        Lars-Peter Clausen <lars@...afoo.de>,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
        letux-kernel@...nphoenux.org, kernel@...a-handheld.com,
        linux-omap@...r.kernel.org
Subject: Re: [PATCH] iio: palmas: shut up warning about calibration mismatch
 (due to noise)

Hi Jonathan,

> Am 20.03.2022 um 16:52 schrieb Jonathan Cameron <jic23@...nel.org>:
> 
> On Tue,  8 Mar 2022 13:53:03 +0100
> "H. Nikolaus Schaller" <hns@...delico.com> wrote:
> 
>> Although technically checking for ADC values below 0 is correct,
>> because they are outside of the calibration values, there is usually
>> noise which spuriously fills the console log with error messages if
>> calculated input voltage gets close to 0V.
>> 
>> Ignore small negative calculated values, but clamp them to 0.
>> 
>> Signed-off-by: H. Nikolaus Schaller <hns@...delico.com>
> Hi.
> 
> Should we treat this as a fix or a cleanup?
> 
> I don't mind either way.

I don't mind either since we have it for long time in our distribution kernel.

BR and thanks,
Nikolaus

> 
> Jonathan
> 
> 
>> ---
>> drivers/iio/adc/palmas_gpadc.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>> 
>> diff --git a/drivers/iio/adc/palmas_gpadc.c b/drivers/iio/adc/palmas_gpadc.c
>> index f9c8385c72d3..bcfa6a7f6cb2 100644
>> --- a/drivers/iio/adc/palmas_gpadc.c
>> +++ b/drivers/iio/adc/palmas_gpadc.c
>> @@ -376,7 +376,8 @@ static int palmas_gpadc_get_calibrated_code(struct palmas_gpadc *adc,
>> 					adc->adc_info[adc_chan].gain_error;
>> 
>> 	if (val < 0) {
>> -		dev_err(adc->dev, "Mismatch with calibration\n");
>> +		if (val < -10)
>> +			dev_err(adc->dev, "Mismatch with calibration var = %d\n", val);
>> 		return 0;
>> 	}
>> 
>