Re: ti_am33x_adc sampling bugs

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I believe the AIN files came from 0020-iio-ti_am335x_adc-Add-IIO-map-interface.patch. The bug is the same reading from in_voltageX_raw files.

On 3/31/2014 12:14 PM, Jonathan Cameron wrote:


On March 31, 2014 9:17:53 AM GMT+01:00, Rob Mosher <nyt@xxxxxxxxxxxxxxxxxxx> wrote:
The following patches were removed and behavior returned to normal.

0019-iio-ti_am335x_adc-Add-continuous-sampling-and-trigge.patch
0020-iio-ti_am335x_adc-Add-IIO-map-interface.patch

Once 19 was re-applied, the bug returned.

It would appear that patch19 is the problem.  On an unrelated note, the

continuous sampling patch seems to still be missing the mode file to
tell it to sample continuously or oneshot in the sysfs directory as
referenced at
http://processors.wiki.ti.com/index.php/AM335x_ADC_Driver%27s_Guide.
Someone should update that wiki page.
Such an attribute was not and will not be
  part of the mainline kernel ABI. Drivers can play fast and loose in staging but to move
  out the ABI must conform to existing definitions or be proposed reviewed and accepted.

I am somewhat confused. Where did the AIN sysfs attributes come from?

Maybe this should be moved to the beta kernel until stable?


Cheers.

On 3/31/2014 12:04 AM, Rob Mosher wrote:
(sorry for the duplicate, got bounces due to HTML encoding)

The specified patch is already included.  The system was running the
latest kernel from Robert Nelson's repo.  Any suggestions?  I'll try
removing some of the patches to see if it fixes this behavior.  I
have a
feeling I know which one is doing it.

Thanks.

output from running patch.sh with source pulled from
https://github.com/beagleboard/kernel/tree/3.8


/home/bbuild/comp/kernel/patches/adc/0017-IIO-ADC-ti_adc-Fix-1st-sample-read.patch:
applied

Just in case, I built and installed the kernel and the same behavior
persisted.

root@rbone:/# uname -a
Linux rbone 3.8.13-00737-g7dfad77 #1 SMP Sun Mar 30 22:11:44 EDT 2014
armv7l GNU/Linux

gpio30 is connected to AIN4 using a voltage divider

root@rbone:/# cd /sys/class/gpio/
root@rbone:/sys/class/gpio# echo 30 > export
root@rbone:/sys/class/gpio# echo BB-ADC >
/sys/devices/bone_capemgr.9/slots
root@rbone:/sys/class/gpio# cd /sys/devices/ocp.3/helper.11/
root@rbone:/sys/devices/ocp.3/helper.11# echo out >
/sys/class/gpio/gpio30/direction

root@rbone:/sys/devices/ocp.3/helper.11# echo 1 >
/sys/class/gpio/gpio30/value
root@rbone:/sys/devices/ocp.3/helper.11# cat AIN4
1460

root@rbone:/sys/devices/ocp.3/helper.11# echo 0 >
/sys/class/gpio/gpio30/value
root@rbone:/sys/devices/ocp.3/helper.11# cat AIN4
0

root@rbone:/sys/devices/ocp.3/helper.11# grep . AIN[0-3] AIN[5-7]
AIN0:1550
AIN1:1213
AIN2:1485
AIN3:795
AIN5:513
AIN6:744
AIN7:1698

root@rbone:/sys/devices/ocp.3/helper.11# echo 1 >
/sys/class/gpio/gpio30/value
root@rbone:/sys/devices/ocp.3/helper.11# cat AIN4
0
root@rbone:/sys/devices/ocp.3/helper.11# cat AIN4
0
root@rbone:/sys/devices/ocp.3/helper.11# cat AIN4
0
root@rbone:/sys/devices/ocp.3/helper.11# cat AIN4
0
root@rbone:/sys/devices/ocp.3/helper.11# cat AIN4
0
root@rbone:/sys/devices/ocp.3/helper.11# cat AIN4
0
root@rbone:/sys/devices/ocp.3/helper.11# cat AIN4
1460

On 3/30/2014 9:16 AM, Zubair Lutfullah wrote:

https://github.com/beagleboard/kernel/blob/3.8/patches/adc/0017-IIO-ADC-ti_adc-Fix-1st-sample-read.patch

IIRC, this patch fixes this issue

Can you compile the kernel from the sources and check?
https://github.com/beagleboard/kernel/tree/3.8

Regards
ZubairLK

On Sun, Mar 30, 2014 at 7:04 AM, Rob Mosher <nyt@xxxxxxxxxxxxxxxxxxx
<mailto:nyt@xxxxxxxxxxxxxxxxxxx>> wrote:

     Just a note, the same behavior persists with BB-ADC dtb and
     reading from in_voltage4_raw


     On 3/30/2014 12:30 AM, Rob Mosher wrote:

         Hello fine developers,

         It seems I've stumbled upon a problem while developing a
full
         featured Ruby gem for the Beaglebone.

         It seems a patch included in the beaglebone kernel causes
some
         issues while reading analog inputs.  Apparently the samples
         get backlogged by the number of adc pins in use.  I'm not
sure
         which patch exactly as there are a number that affect adc
         buffering and I'm not currently setup for kernel building,
         however the below output should detail the problem.

         Using the official Debian image.
         Linux rbone 3.8.13-bone43 #1 SMP Wed Mar 26 14:21:39 UTC
2014
         armv7l GNU/Linux

         Distributor ID: Debian
         Description:    Debian GNU/Linux 7.4 (wheezy)
         Release:        7.4
         Codename:       wheezy

         root@rbone:~# echo cape-bone-iio >
         /sys/devices/bone_capemgr.9/slots

         This is the normal and expected behavior.

         1.8v applied to AIN4
         root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
         1798

         0v applied to AIN4
         root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
         0

         1.8v applied to AIN4
         root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
         1798

         0v applied to AIN4
         root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
         0

         So far working as intended....  Now reading from the other
pins.

         root@rbone:/sys/devices/ocp.3/helper.12# grep . AIN[0-3]
AIN[5-7]
         AIN0:1563
         AIN1:1221
         AIN2:1487
         AIN3:789
         AIN5:514
         AIN6:743
         AIN7:1698

         Now applying 1.8v to AIN4
         root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
         0
         root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
         0
         root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
         0
         root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
         0
         root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
         0
         root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
         0
         root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
         1798

         Now applying 0v to AIN4

         root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
         1460
         root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
         1798
         root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
         1798
         root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
         1460
         root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
         1460
         root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
         1460
         root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
         0



         And another example, showing relation to the number of pins
in
         use.

         1.8v to AIN4
         root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
         1460
         root@rbone:/sys/devices/ocp.3/helper.12# grep . AIN[0-3]
         AIN0:1697
         AIN1:1298
         AIN2:1524
         AIN3:816
         root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
         1798

         0v to AIN4
         root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
         1798
         root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
         1460
         root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
         1460
         root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
         1460
         root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
         0

         1.8v to AIN4
         root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
         0
         root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
         0
         root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
         0
         root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
         0
         root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
         1798

         --         Rob Mosher
         Senior Network and Software Engineer
         Hurricane Electric / AS6939






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