AM5728 Linux PWM Driver

Mike Danby

Other Parts Discussed in Thread: AM5728

Hello,

I am using the Processor SDK for AM57x Sitara™ Processors - Linux on a am5728 custom SBC, and being new to Linux kernel development I am struggling with getting the PWM driver up and running.
I believe the drivers in question pwm-tipwmss.c and pwm-tiehrpwm.c are being included in the kernel and the following information is included in the device tree:

       epwmss0: epwmss@4843e000 {
           compatible = "ti,dra7xx-pwmss", "ti,am33xx-pwmss";
           reg = <0x4843e000 0x30>;
           ti,hwmods = "epwmss0";
           #address-cells = <1>;
           #size-cells = <1>;
           status = "disabled";
           ranges = <0x4843e100 0x4843e100 0x80 /* ECAP */
                  0x4843e180 0x4843e180 0x80 /* EQEP */
                  0x4843e200 0x4843e200 0x80>;/* EHRPWM */

           ehrpwm0: ehrpwm@4843e200 {
               compatible = "ti,dra7xx-ehrpwm",
                         "ti,am33xx-ehrpwm";
               #pwm-cells = <3>;
               reg = <0x4843e200 0x80>;
               ti,hwmods = "ehrpwm0";
               status = "disabled";
           };
       };

       epwmss1: epwmss@48440000 {
           compatible = "ti,dra7xx-pwmss", "ti,am33xx-pwmss";
           reg = <0x48440000 0x30>;
           ti,hwmods = "epwmss1";
           #address-cells = <1>;
           #size-cells = <1>;
           status = "disabled";
           ranges = <0x48440100 0x48440100 0x80   /* ECAP */
                  0x48440180 0x48440180 0x80   /* EQEP */
                  0x48440200 0x48440200 0x80>; /* EHRPWM */

           ehrpwm1: ehrpwm@48440200 {
               compatible = "ti,dra7xx-ehrpwm",
                         "ti,am33xx-ehrpwm";
               #pwm-cells = <3>;
               reg = <0x48440200 0x80>;
               ti,hwmods = "ehrpwm1";
               status = "disabled";
           };
       };

       epwmss2: epwmss@48442000 {
           compatible = "ti,dra7xx-pwmss", "ti,am33xx-pwmss";
           reg = <0x48442000 0x30>;
           ti,hwmods = "epwmss2";
           #address-cells = <1>;
           #size-cells = <1>;
           status = "disabled";

           ranges = <0x48442100 0x48442100 0x80   /* ECAP */
                  0x48442180 0x48442180 0x80   /* EQEP */
                  0x48442200 0x48442200 0x80>; /* EHRPWM */

           ehrpwm2: ehrpwm@48442200 {
               compatible = "ti,dra7xx-ehrpwm",
                         "ti,am33xx-ehrpwm";
               #pwm-cells = <3>;
               reg = <0x48442200 0x80>;
               ti,hwmods = "ehrpwm2";
               status = "disabled";

           };
       };

can anyone point out what I am missing from the device tree or is there another problem ?

over 9 years ago

0 Cvetolin Shulev-XID over 9 years ago

TI__Guru 65405 points

Hi Mike,

I don't find any errors in your configuration of device tree. I suggest you to verify PWM functionality of your board as follow instructions in the linked PWMSS Driver's Guide:
processors.wiki.ti.com/.../AM335x_PWM_Driver's_Guide

BR
Tsvetolin Shulev

0 Mike Danby over 9 years ago in reply to Cvetolin Shulev-XID

Prodigy 20 points

There must be something wrong as the eHRPWM device dose not appear in the SYSFS interface. There is no messages in the dmesg log relating the PWM devices.

0 Yordan Kovachev over 9 years ago in reply to Mike Danby

TI__Guru**** 161600 points

Hi,

Those are dtsi entries. You missed configuring the pwm pinmux, if pinmuxing is needed. Also if you check your entries, you'll see that you have status="disabled", which means that the IP is not used by your system.

You should add the following in your .dts file, i.e. to enable epwmss1 and ehrpwm1:
&epwmss1 {
status = "okay";

ehrpwm1: ehrpwm@48440200 {
status = "okay";
};
};

This will tell linux that your pwm driver is used in the system and will bind it to pwm-tipwmss.c and pwm-tiehrpwm.c and also create the correct sysfs entries.

Best Regards,
Yordan

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AM5728 Linux PWM Driver