Re: ti_am33x_adc sampling bugs

Jonathan Cameron
2014-03-31T16:15:05Z

On March 31, 2014 9:17:53 AM GMT+01:00, Rob Mosher <nyt@countercultured.net> 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@countercultured.net
>>> <mailto:nyt@countercultured.net>> 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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