Hi TJF, thanks for your note. Are you saying that the only way to get PWM
in a 4.x kernel is by modifying am33xx-clocks.dtsi? Also, how can I verify
whether the register is set correctly?
Thanks,
Justin
On Friday, March 31, 2017 at 9:48:33 AM UTC-7, TJF wrote:
>
> Hi Justin!
>
> The initial device tree changed between kernel 3.8 and 4.x. In 4.x the
> Control Module register *pwmss_ctrl* (@664h) gets cleared at boot. This
> register can get used to sychronize several PWM subsystems. A feature that
> isn't supported by the kernel nor by any of it's drivers. So no reason to
> change the initial state and clear that register. This just disables all
> PWM subsystems and makes kernel versions incompatible. (You may call it an
> official kernel virus).
>
> Anyway, in order to get the PWM subsystems working in kernel 4.x you have
> to make sure that the register doesn't get cleared at boot. Ie. you can
> invert the bit-logic. Therefor download the device tree sources, edit file
> *am33xx-clocks.dtsi*, find the following nodes and make them look like (=
> add tag *ti,set-bit-to-disable)*
>
> ehrpwm0_tbclk: ehrpwm0_tbclk@44e10664 {
> #clock-cells = <0>;
> compatible = "ti,gate-clock";
> clocks = <&l4ls_gclk>;
> ti,bit-shift = <0>;
> ti,set-bit-to-disable;
> reg = <0x0664>;
> };
>
> ehrpwm1_tbclk: ehrpwm1_tbclk@44e10664 {
> #clock-cells = <0>;
> compatible = "ti,gate-clock";
> clocks = <&l4ls_gclk>;
> ti,bit-shift = <1>;
> ti,set-bit-to-disable;
> reg = <0x0664>;
> };
>
> ehrpwm2_tbclk: ehrpwm2_tbclk@44e10664 {
> #clock-cells = <0>;
> compatible = "ti,gate-clock";
> clocks = <&l4ls_gclk>;
> ti,bit-shift = <2>;
> ti,set-bit-to-disable;
> reg = <0x0664>;
> };
>
> Then compile and install the binary trees. PWM subsystems will work after
> reboot.
>
> Regards
>
--
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/0c5efa6d-0b91-4c45-a595-072eedc54c43%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
