PWM is not working on several latest JetPack Versions with Jetson Nano Dev Kit

Robotics & Edge Computing Jetson & Embedded Systems Jetson Nano
, ,
1

Hello,

We’ve tested PWM and LED with 3ea of jetson nano dev kit.
The result of PWM function test as below for each JetPack version :
PWM is working => JP-4.6 / JP-4.6.1 / JP-4.6.2
PWM is not working => JP-4.6.3 / JP-4.6.4 / JP-4.6.5

I can see 0x700031fc is set to 0x00000001 after PWM is enabled from jetson-io.py on all of 6 jetpack versions.
The below image from JetPack 4.6.4 installed Jetson Nano Dev Kit.

image
image1854×475 126 KB

Register’s values are same for PWM with All JetPack versions what I’ve tested.
But the led light doesn’t come up on JetPack versions above JP-4.6.3

And It has to install with Recovery mode for lower version below JP-4.6.2 if the board is installed for latest version above JP-4.6.3 before.
The installed JetPack version on QSPI affect PWM, either.

4

Sorry for the late response.
Is this still an issue to support? Any result can be shared?

5

We are using JP-4.6.2.
It is fine for us in our work process right now.
But It is still an issue technically.

I didn’t capture result for all versions.
In case of output checking, we was just seeing the led.
So, there is nothing special more for sharing in now.
If you want any other result information?
Please, let me know. I can share it.

6

Hi sumin.lee1,

Which PWM are you using for LED? (7000a000.pwm or 70110000.pwm)

Have you tried to get a scope to measure the waveform at this moment?

Please share the full dmesg in both release(JP4.6.2(working) and JP4.6.3(not working)) for further check.

7

We don’t have scope. we can check output through led only now.
And 70110000.pwm device is busy when it export.
I’m testing only pin 32 and pin 33 on GPIO Expansion.
Both pins looks 7000a000.pwm.
image
On the Jetson.GPIO, result of pin 33 as same as pin 32.

And I cross checked between sd card and qspi(dev kit).
The result as belown:
QSPI - 4.6.2 / JetPack - 4.6.2 => It works
QSPI - 4.6.2 / JetPack - 4.6.3 => It works
QSPI - 4.6.3 / JetPack - 4.6.2 => It doesn’t works
QSPI - 4.6.3 / JetPack - 4.6.3 => It doesn’t works

And the dmesg are here
dmesg_jp4.6.2.txt (59.4 KB)
dmesg_jp4.6.3.txt (59.4 KB)
dmesg_qspi-4.6.2_sdcard-4.6.3.txt (57.8 KB)
dmesg_qspi-4.6.3_sdcard-4.6.2.txt (59.4 KB)

Maybe, the issue from device tree as I guess.

8

Those are device tree from each installed filesystem.
I extracted the device-tree file after the pin 32 and 33 is enabled for PWM from jetson-io.py.
device-tree-jp462.dts.txt (322.3 KB)
device-tree-jp463.dts.txt (322.4 KB)

“lcd_bl_pwm_pv0” are different as below:

// JetPack-4.6.2

lcd_bl_pwm_pv0 {
nvidia,enable-input = <0x0>;
nvidia,pins = “lcd_bl_pwm_pv0”;
nvidia,tristate = <0x1>;
nvidia,function = “rsvd3”;
nvidia,pull = <0x1>;
};

// JetPack-4.6.3

lcd_bl_pwm_pv0 {
nvidia,enable-input = <0x1>;
nvidia,pins = “lcd_bl_pwm_pv0”;
nvidia,tristate = <0x0>;
nvidia,function = “rsvd3”;
nvidia,pull = <0x1>;
};

9

From the dmesg you shared, it seems the similar for all 4 combinations.

Have you tried to use the lcd_bl_pwm_pv0 configuration of JP4.6.2 to JP4.6.3 to check if it could help in your case?

and I found this node(lcd_bl_pwm_pv0) is under unused_lowpower in JP4.6.2, but under common in JP4.6.3.

10

I have to try nothing yet for custom configuration.
I did only cross-equip SD Card and Board with default BSP.
As I known, Jetson Nano needs to build L4T kernel for applying custom pinmux.
Now, I’m doing another work right now.
Maybe, I can do this test 2 weeks later at least.

11

Yes, you have to rebuild kernel dtb to apply the change for pinmux.
Okay, you can also just use JP4.6.2 now and open another topic 2 weeks later if you want to do further debug on this issue.

13

This topic was automatically closed 14 days after the last reply. New replies are no longer allowed.