AM6548: Not able to set PRU GPIO value

sarfaraz shaikh

Part Number: AM6548

Hi TI,

I am trying to set the PRG1_PRU0GPO5 (pad no AF27) value to 1 but system is automatically making it 0. we tried to remove the Pru Ethernet driver and also we tried to remove other pru related drivers but Linux is not able to set the value 1.

what can be the issue here why linux is not able to set the value of PRU GPIO.

below is the dts snapshot

AM65X_IOPAD(0x00f4, PIN_OUTPUT, 7) /* (AF27) GPIO0_61

Thanks

8 months ago

0 Nick Saulnier 8 months ago

TI__Guru** 110030 points

Hello,

To clarify, you are trying to use the GPIO signal from Linux, right? NOT use the PRU core to write values to the pins?

What version of Linux kernel are you using?

Regards,

Nick

0 sarfaraz shaikh 8 months ago in reply to Nick Saulnier

Expert 1546 points

Hey Nick, Thanks for connecting. Yes we are using the GPIO signals from Linux. Linux version is linux-5.10.100 which was part of 8.2 SDK.

Regards,

Sarfaraz

0 Shriya Surti 8 months ago in reply to sarfaraz shaikh

TI__Intellectual 2150 points

Hi Sarfaraz,

Please note AM65 has limited design support as seen on the product page: AM6548 data sheet, product information and support | TI.com. I suggest taking a look at the following FAQ to see how to set the pinmux correctly and establish a reference node (look under "GPIOs were selected to use in Linux, how can the GPIO be enabled in the Linux device tree"): [FAQ] PROCESSOR-SDK: Getting Started with GPIOs in Linux using the AM62 and AM64 Family Processors - Processors forum - Processors - TI E2E support forums. Since libgpiod does not apply to your older kernel version, make sure to use sysfs to try setting the GPIO value. More information on SYSFS is available within the FAQ as well.

Best Regards,

Shriya

0 sarfaraz shaikh 8 months ago in reply to Shriya Surti

Expert 1546 points

We are trying through sys interface. GPIO is a simple thing. Other GPIO are working properly only issue is with PRU GPIO controlled from Linux.

0 Shriya Surti 8 months ago in reply to sarfaraz shaikh

TI__Intellectual 2150 points

Hi Sarfaraz,

Since other GPIOs are working as expected, there is a possible pinmux conflict elsewhere in the device tree. Could you please check if the same address (0x00f4) is being configured anywhere else in your dts file?

Additionally, it would be helpful to use devmem2 to read back the corresponding pinmux register on your board at runtime and confirm what mode and direction are actually being applied after boot. This will help determine whether the pinmux is being overwritten.

Regards,
Shriya

0 Shankar Boyane 8 months ago in reply to Shriya Surti

Prodigy 20 points

Hello Shirya,

We have verified and confirmed the address 0x00f4 is not used anywhere else in our device tree file. Additionally, we are observing the same issue on the TI Evaluation board as well. This suggests that the problem might not be specific to our custom hardware but could be related to the pinmux configuration or driver behavior.

Please let us know if you recommend any additional checks or if there are known limitations with this pinmux setting on the TI platform.

0 Shriya Surti 8 months ago in reply to Shankar Boyane

TI__Intellectual 2150 points

Hi Shankar,

One thing to note is that on the EVM, the pinmux register at 0x00f4 is not configured by default. The register is not explicitly set during early boot, just trying to set the pin at runtime will not work as expected. Can you verify the register value at runtime using devmem2? Please read the register value once before any GPIO interaction, and then read it again after trying to set it. This will show whether the expected mode and direction are actually being applied.

Regards,

Shriya

0 Shankar Boyane 8 months ago in reply to Shriya Surti

Prodigy 20 points

Hello Shriya,

We were able to enable GPIO5 by writing directly to the register (0x00f4) using the devmem2 on our customized board:

devmem2 0x0011C0f4 w 0x08050007

Additionally, we were able to set the value on the same register successfully.

Thanks for your support!

0 Shriya Surti 8 months ago in reply to Shankar Boyane

TI__Intellectual 2150 points

Hi Shankar,

Great to hear, glad we could help.

Shriya