linux-kernel - Re: [PATCH v4] iio: adc: Add TI ADS1015 ADC driver support

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Message-ID: <20160301005032.GA15476@deathstar>
Date:	Mon, 29 Feb 2016 18:50:32 -0600
From:	Michael Welling <mwelling@...e.org>
To:	Daniel Baluta <daniel.baluta@...el.com>
Cc:	jic23@...nel.org, knaack.h@....de, lars@...afoo.de,
	pmeerw@...erw.net, linux-kernel@...r.kernel.org,
	linux-iio@...r.kernel.org, lucas.demarchi@...el.com,
	linux@...ck-us.net, eibach@...ys.de
Subject: Re: [PATCH v4] iio: adc: Add TI ADS1015 ADC driver support

On Fri, Feb 05, 2016 at 03:17:18PM +0200, Daniel Baluta wrote:
> The driver has sysfs readings with runtime PM support for power saving.
> It also offers buffer support that can be used together with IIO software
> triggers.
>

Daniel,

So I noticed something yesterday while testing new boards.
The channels are occassionally swapping when accessing data from multiple channels.

I wrote a simple bash script to demonstrate.

root@...gonboard-410c:~# cat test-analog.sh 
while [ 1 ]; do
voltage0=`cat /sys/bus/iio/devices/iio\:device0/in_voltage0_raw`
voltage1=`cat /sys/bus/iio/devices/iio\:device0/in_voltage1_raw`
voltage2=`cat /sys/bus/iio/devices/iio\:device0/in_voltage2_raw`
voltage3=`cat /sys/bus/iio/devices/iio\:device0/in_voltage3_raw`
echo ain0 = $voltage0 ain1 = $voltage1 ain2 = $voltage2 ain3 = $voltage3
done
root@...gonboard-410c:~# ./test-analog.sh 
ain0 = 266 ain1 = 291 ain2 = 268 ain3 = 291
ain0 = 287 ain1 = 294 ain2 = 289 ain3 = 292
ain0 = 284 ain1 = 294 ain2 = 286 ain3 = 0
ain0 = 285 ain1 = 288 ain2 = 287 ain3 = 0
ain0 = 287 ain1 = 286 ain2 = 287 ain3 = 0
ain0 = 285 ain1 = 287 ain2 = 293 ain3 = 0
ain0 = 0 ain1 = 289 ain2 = 293 ain3 = 0
ain0 = 0 ain1 = 289 ain2 = 290 ain3 = 291
ain0 = 287 ain1 = 289 ain2 = 289 ain3 = 0
ain0 = 0 ain1 = 285 ain2 = 288 ain3 = 0
ain0 = 285 ain1 = 286 ain2 = 288 ain3 = 0
ain0 = 286 ain1 = 288 ain2 = 285 ain3 = 0
ain0 = 287 ain1 = 293 ain2 = 289 ain3 = 292
ain0 = 288 ain1 = 292 ain2 = 287 ain3 = 293
ain0 = 286 ain1 = 287 ain2 = 289 ain3 = 0
ain0 = 283 ain1 = 289 ain2 = 289 ain3 = 0
ain0 = 0 ain1 = 287 ain2 = 287 ain3 = 0
ain0 = 0 ain1 = 286 ain2 = 288 ain3 = 0
ain0 = 286 ain1 = 288 ain2 = 289 ain3 = 0
ain0 = 287 ain1 = 286 ain2 = 290 ain3 = 0
ain0 = 289 ain1 = 291 ain2 = 287 ain3 = 0
ain0 = 284 ain1 = 286 ain2 = 292 ain3 = 0
ain0 = 286 ain1 = 291 ain2 = 289 ain3 = 292
ain0 = 284 ain1 = 292 ain2 = 291 ain3 = 291
ain0 = 285 ain1 = 287 ain2 = 287 ain3 = 0
ain0 = 0 ain1 = 289 ain2 = 291 ain3 = 0
ain0 = 0 ain1 = 288 ain2 = 291 ain3 = 0
ain0 = 0 ain1 = 286 ain2 = 288 ain3 = 0
ain0 = 286 ain1 = 287 ain2 = 290 ain3 = 0
ain0 = 286 ain1 = 286 ain2 = 288 ain3 = 0
ain0 = 286 ain1 = 286 ain2 = 287 ain3 = 0
ain0 = 285 ain1 = 289 ain2 = 288 ain3 = 288
ain0 = 289 ain1 = 292 ain2 = 289 ain3 = 293
ain0 = 287 ain1 = 292 ain2 = 290 ain3 = 0
ain0 = 286 ain1 = 286 ain2 = 291 ain3 = 0
ain0 = 0 ain1 = 287 ain2 = 290 ain3 = 0
ain0 = 0 ain1 = 286 ain2 = 289 ain3 = 0
ain0 = 284 ain1 = 285 ain2 = 292 ain3 = 0
ain0 = 285 ain1 = 289 ain2 = 289 ain3 = 0
ain0 = 287 ain1 = 287 ain2 = 287 ain3 = 0
ain0 = 287 ain1 = 291 ain2 = 287 ain3 = 291
ain0 = 288 ain1 = 291 ain2 = 290 ain3 = 293
ain0 = 285 ain1 = 290 ain2 = 287 ain3 = 292
ain0 = 285 ain1 = 289 ain2 = 289 ain3 = 292
ain0 = 286 ain1 = 289 ain2 = 288 ain3 = 0
ain0 = 0 ain1 = 286 ain2 = 291 ain3 = 0
ain0 = 0 ain1 = 287 ain2 = 291 ain3 = 0
ain0 = 287 ain1 = 286 ain2 = 291 ain3 = 0
ain0 = 288 ain1 = 286 ain2 = 289 ain3 = 0
ain0 = 284 ain1 = 289 ain2 = 288 ain3 = 0
ain0 = 287 ain1 = 290 ain2 = 287 ain3 = 292
ain0 = 285 ain1 = 292 ain2 = 289 ain3 = 292
ain0 = 289 ain1 = 292 ain2 = 290 ain3 = 0
.
.

The in_voltage3_raw channel is connected to GND the rest are left floating.
This does not happen if only one channels is accessed at a time.

I have not yet found the solution. Please left me know if this can be
duplicated on your end.

Regards,

Michael