AM4378: Using the Hardware UART peripheral of the PRU-ICSS

Part Number: AM4378

I need to use the UART hardware peripheral of the PRU-ICSS in a custom board running Linux. Could you please guide me on how to get started.

Hi,

The PRU-ICSS UART is enabled for AM335x. Following are the kernel patches which enable it for AM335x. I think you only need modify AM437x device tree to add the pruss_uart node and set the pinmux.

https://git.ti.com/cgit/ti-linux-kernel/ti-linux-kernel/log/?h=ti-linux-5.4.y&qt=grep&q=pruss+uart

Here is the documentation about PRU-ICSS UART driver on AM335x.

https://software-dl.ti.com/processor-sdk-linux/esd/docs/07_03_00_005/linux/Foundational_Components/PRU-ICSS/Linux_Drivers/pruss-uart.html

Hi Bin Liu,

Thank you for your inputs. Could you also please suggest how to get the corresponding PRU firmware that implements the hardware uart ?

Thanks,

Mukundan

Hi,

Mukundan Parthasarathy said:

How do I use this driver for sending and receiving bytes, as I do not see any functions in it for Open, Read, Write. 

In the same way as using other UARTs. This driver will expose the PRU UART device node /dev/ttyS*.

Mukundan Parthasarathy said:

The driver seems to be setting baud to 38,400. If I replace this number by 115200, would that work?

No, the number 38400 you see in the driver source code does not hard code the baud rate. Don't change the code. The buad rate is set in user space applications.

Mukundan Parthasarathy said:

Is there a demo app that uses this driver?

Any Linux UART program can use this PRU UART device.

Mukundan Parthasarathy said:

Do I need to access the 16550 registers? If so how do I do it?

No, I believe you don't need to change anything in the driver, just add the device tree bindings to enable this PRU UART on your platform.

Mukundan Parthasarathy said:

Does the driver handle Rx and Tx interrupts automatically through pruss_intc driver?

Yes.

Thank you, Bin Liu. Your help is much appreciated.

Mukundan