On Wed, Sep 27, 2017 at 1:22 PM, William Hermans <[email protected]> wrote:
> So a few things to note about pwm behavior on the latest stretch image > versus Jessie. > Obviously, Jessie by default runs an older kernel. 4.4.x versus 4.9.x. > > > First, > > Jessie: > root@wgd:~# uname -r > 4.4.68-ti-r111 > root@wgd:~# lsmod |grep pwm > pwm_tiehrpwm > > Stretch: > root@wgd:~# uname -r > 4.9.50-ti-r61 > root@wgd:~# lsmod |grep pwm /* No output */ > > Here, I'm thinking the PWM module is built into the kernel. Because I'm > running the same custom overlay on both boards, and both have a populated > sysfs entry for pwm. However there is a difference. > > Jessie: > root@wgd:~# ls /sys/class/pwm/pwmchip0 > device export npwm power pwm0 pwm1 subsystem uevent unexport > > Stretch: > root@wgd:~# ls /sys/class/pwm/pwmchip0 > device export npwm power pwm0 subsystem uevent unexport > > Here, initially, there was no pwm0 substructure. This populated after I > ran echo '0' > /sys/class/pwm/pwmchip0/export as root. Further examination > seems to indicate that pwm0 channel A is fully functional. > > root@wgd:~# ls /sys/class/pwm/pwmchip0/pwm0/ > capture duty_cycle enable period polarity power uevent > > But I have not physically tested the hardware just yet. > > So my questions are this. What's the difference ? Does this have something > to do with the module being built into the kernel. or is there some kind of > overlay change I'm not currrently aware of ? > > config-pin for my project here is not an option . . . And in fact, > cape_universal is disabled via the uboot envrorinment file. > > Everything else seems to be exactly the same as far as I can tell, but I > have not poured over the whole system just yet. Seems to be pretty stable > too, but I've only been running the latest console stretch image for a few > days now. > Well there does seem to be a small difference between the two in the subchannel directory too. Jessie: root@wgd:~# ls /sys/class/pwm/pwmchip0/pwm0/ duty_cycle enable period polarity power uevent Stretch: root@wgd:~# ls /sys/class/pwm/pwmchip0/pwm0/ capture duty_cycle enable period polarity power uevent But I do not have a problem with that so much, as long as it doesnt interfere with pwm functionality. -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/CALHSORqa7OtAX9SpkiDeAfNUnGtQBuKPWDYXrQvC89JD4D9XNQ%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
