AGX Thor T5000 Enable PWM2 no output

Robotics & Edge Computing Jetson Systems Jetson Thor
,
1

Hi NVTeam,

On my T5000 OEM Board with JetPack7.2, I want to use GPIO27(H52) pin as PWM2 function.
I have change the PINMUX spreadsheet and Kernel DTS as below:

image
image1565×333 152 KB

#include "tegra264-p4071-0000+p3834-0008-nv.dts"

/ {
        bus@0 {
                pwm@810c5e0000 {
	            status = "okay";
                };
       };
};

And in the OS, I can see the pinmux and pwmchip all worked,

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But, I can’t measure any waveform from the GPIO27 pin with the oscilloscope?
Is there anything wrong with my operation?

By the way, in order to test my hardware connection:
I set the GPIO27(H52) pinmux as GPIO, and pull HIGH and LOW with gpiod tools.
I can measure the changes in voltage levels using a multimeter.
This should mean that there is no problem with my hardware connection.

4

Hi kang.pan,

Do you have the AGX Thor devkit board to reproduce the similar issue?

Your operation and commands look good to me.
Could you try configuring other period/duty_cycle value to check if there’s any PWM signal output?

5

Hi KevinFFF,

This signal on the DevKit is not routed externally, so it cannot be tested.

I have test the below period/duty_cycle values:
period=10000, duty_cycle=5000, Yes
period=100000, duty_cycle=50000, Yes
period=1000000, duty_cycle=500000, Yes
period=10000000, duty_cycle=5000000, No

I think it should be same as this post, and I know what to do now.
Many Thanks!

6

Hi，
I follow the Dev Guide, to set the PWM2 output 30Hz.

Test Case 1:
Set the DTS property nvidia,pwm-depth = <65535>;
When I set the 30Hz output in sysfs: period=33333333, duty_cycle=16666666,
I can measure the PWM output with oscilloscope， it is 29.46Hz.

/ {
        bus@0 {
                pwm@810c5e0000 {
                         assigned-clocks = <&bpmp TEGRA264_CLK_PWM2>;
                         assigned-clock-parents = <&bpmp TEGRA264_CLK_OSC>;
                         nvidia,pwm-depth = <65535>;
                         status = "okay";
                };
        };
};

Test Case 2:
Set the DTS property nvidia,pwm-depth = <449>; to get more precise output frequency.
When I set the 30Hz output in sysfs: period=33333333, duty_cycle=16666666,
I can not measure the any output from the same pin.

/ {
        bus@0 {
                pwm@810c5e0000 {
                         assigned-clocks = <&bpmp TEGRA264_CLK_PWM2>;
                         assigned-clock-parents = <&bpmp TEGRA264_CLK_OSC>;
                         nvidia,pwm-depth = <449>;
                         status = "okay";
                };
        };
};

When I set the nvidia,pwm-depth = <449>;, I have tested more target freq, the result is as below:

Target Freq PFM Measure with Oscilloscope
1kHz 59 ✅
~469Hz 127 ✅
~234Hz 255 ✅
~117Hz 511 ❌ No output
100Hz 599 ❌ No output
30Hz 1999 ❌ No output

Seems the PFM range is only 0 ~ 255 (8bit width).
This is incomapatible with the .scale_width = 16 in tegra-pwm.c seems inconsistent with actual measurements.

static const struct tegra_pwm_soc tegra264_pwm_soc = { 
        .channel_offset = 0,
        .depth_offset = 4,
        .depth_shift = 15, 
        .depth_width = 16, 
        .duty_shift = 16, 
        .duty_width = 16, 
        .enb_offset = 4,
        .num_channels = 1,
        .scale_shift = 0,
        .scale_width = 16, 
        .has_depth_csr = true,
};
7

Hi kang.pan,

We can reproduce the similar issue as yours.
I’m checking this with internal team.

Before that, you can simply configure nvidia,pwm-depth = <0xe0f>; for exact 30Hz output.
27000000Hz/(1+3599)/(1+249) = 30Hz
I have verified it working on my setup:

image
image952×741 34.8 KB

8

Hi KevinFFF,
OK，got it! Thanks for your reply.

10

Hi kang.pan,

We have identified the cause of the “No output” issue seen with some pwm-depth and PFM combinations on Thor. On Thor, the hardware requires PWM_DEPTH >= PFM; otherwise, no waveform is generated

Please check whether you observe results similar to the ones below:

Parent Clock - OSC (Hz) Target PWM output
frequency (Hz)		 PWM_DEPTH PFM Waveform Result
27000000 30 3599 249 Pass
27000000 30 1799 499 Pass
27000000 30 999 899 Pass
27000000 30 899 999 No Output