AM3352: eHRPwm1:A/B dual channel output issue

user6563005

Prodigy 60 points

Part Number: AM3352
Other Parts Discussed in Thread: AM3358

Dear sir,

The eHRPwm1:A is working good! And we recently added eHRPwm1:B to our board, but now we encounter an issue.

When both channels are stopped, then start any of channel, the issue appear: Both channel now work.

I have "cat /sys/class/pwm/ehrpwm.1:0/run" and "cat /sys/class/pwm/ehrpwm.1:1/run"，one is '1', but another is '0'。

There is a printk of "PWMSS1 registers" and "eHRPwm1 registers" after starting one of the channel (eHRPwm.1:0):

Any advise or infomation would be appreciated !

over 5 years ago

0 Nick Saulnier over 5 years ago

TI__Guru** 108980 points

What version of software are you using?

Regards,

Nick

0 user6563005 over 5 years ago in reply to Nick Saulnier

Prodigy 60 points

Hi Nick,

Nick Saulnier said:
What version of software are you using?

The sdk file name is "ti-sdk-am335x-evm-06.00.00.00".

After debug, I found maybe AQCSFRC value been cleared to zero is a cause， it's value changed from 0x5 to 0. And this happend in the method ehrpwm_aq_set_csfrc_load_mode()，which called by ehrpwm_channel_output_enable().

I saved the AQCSFRC value , and restored it after ehrpwm_aq_set_csfrc_load_mode()，the issue diappeared! But i'm not sure this changing is good enough, will you help me analyze this!

Thanks a lot!

Regards.

0 user6563005 over 5 years ago in reply to Nick Saulnier

Prodigy 60 points

Hi Nick,

After my searching, I found another very similar issue been asked, it's AM3358, maybe my issue is also a SDK bug.

https://e2e.ti.com/support/processors/f/791/t/691603?tisearch=e2e-sitesearch&keymatch=ehrpwm

Regards.

0 Nick Saulnier over 5 years ago in reply to user6563005

TI__Guru** 108980 points

Hello,

Please note that AM335x SDK 6.0 (Linux kernel version 3.2) is very old software. We don't support it any more, so I am limited in how much assistance I can offer. AM335x SDK was replaced by Processor SDK AM335x.

I suspect you are seeing the same behavior as we saw in that post you linked (That post used Linux Processor SDK AM335x 4.3, which uses Linux kernel version 4.9). The latest Linux Processor SDK AM335x 6.3 (Linux 4.19) has many changes to drivers/pwm/pwm-tiehrpwm.c. That includes changes to function ehrpwm_pwm_disable() that are similar to (but not the same as) the patch we posted on that thread.

Your issue should be fixed by moving to the latest SDK release. If you can't do that, try patching the kernel driver using later versions of the driver as a guide. However, I will not be able to help debug the process of patching old drivers.

Regards,

Nick

0 user6563005 over 5 years ago in reply to Nick Saulnier

Prodigy 60 points

Hi Nick,

Thank you a lot for giving me an excellent guild, following this, my issue has been resolved now!

Regards.

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AM3352: eHRPwm1:A/B dual channel output issue