AM6442: Issue on UART3

Thinh Nguyen

Intellectual 825 points

Part Number: AM6442

Hello TI supporters,

I have a AM64x-evm Kit,

I am testing uart3 on Linux SDK8.0 as below:

1. add node inside k3-am642-evm.dts

main_uart3_pins_default: main-uart3-pins-default {
		pinctrl-single,pins = <
			AM64X_IOPAD(0x0248, PIN_INPUT, 4) /* (D16 )UART1_CTSn.UART3_RXD */
			AM64X_IOPAD(0x024c, PIN_OUTPUT, 4) /* (E16) UART1_RTSn.UART3_TXD */
		>;
	};
&main_uart3 {
	status = "okay";
	pinctrl-names = "default";
	pinctrl-0 = <&main_uart3_pins_default>;
};

2. Build and copy dtb file inside the /root/boot/ and then reboot board.

3. testing UART3

root@am64xx-evm:~# cat /dev/ttyS5& echo "dsafdsadfsaf" > /dev/ttyS5
[5] 1079
root@am64xx-evm:~# cat /dev/ttyS2& echo "dfsafsaf" > /dev/ttyS2
[6] 1085
dfsafsaf

Nothing on the console,

I also open another minicom with /dev/ttyUSB3 but nothing to show.

I also test show devicetree infor by:

root@am64xx-evm:~# cat /proc/device-tree/bus@f4000/serial@2830000/status   
okay

On the am64x-evm board, UART3 connect to FTD chip with device file on PC is /dev/ttyUSB3 that is comfortable for testing.

But I don't know why UART3 can not work . Di you already tested UART3 on evm board yet?

I am wondering if the pin function is configurated correctly? Do I need to configure inside U-Boot?

over 4 years ago

0 Thinh Nguyen over 4 years ago

Intellectual 825 points

I setup more command stty -F /dev/ttyS5 11500, sending/receiving data on UART3 properly.

I have a question as below:

in the k3-am64-main.dtsi

main_uart3: serial@2830000 {
		compatible = "ti,am64-uart", "ti,am654-uart";
		reg = <0x00 0x02830000 0x00 0x100>;
		reg-shift = <2>;
		reg-io-width = <4>;
		interrupts = <GIC_SPI 181 IRQ_TYPE_LEVEL_HIGH>;
		clock-frequency = <48000000>;
		current-speed = <115200>;
		power-domains = <&k3_pds 154 TI_SCI_PD_EXCLUSIVE>;
		clocks = <&k3_clks 154 0>;
		clock-names = "fclk";
	};

Bouadrate:
current-speed = <115200>;

Why current-speed is 115200 in dtb but also need to set the stty -F /dev/ttyS5 115200

for UART3. please explain me.

0 Abin Raj over 4 years ago in reply to Thinh Nguyen

Prodigy 160 points

Hi Thinh Nguyen Uart3 & 5 is pinmuxed with SD card right ?

Were you able to send and receive in UART3 with the above changes ? I am also looking to get Uart3 & 5 working

0 Thinh Nguyen over 4 years ago in reply to Abin Raj

Intellectual 825 points

Hello Abin Raj,

UART3 works well on am64x-evm board with above setting

0 Bin Liu over 4 years ago in reply to Thinh Nguyen

TI__Guru**** 177981 points

Hi Thinh,

Instead of "stty -F /dev/ttyS5 115200", if you run command "stty -F /dev/ttyS5" (without the baud rate) after booted the board, what is the baud rate reported? I believe it is 9600, not 115200.

0 Thinh Nguyen over 4 years ago in reply to Bin Liu

Intellectual 825 points

Hello Bin Liu,

Yes, baud rate after booted is 9600. That means the parameter current-speed = <115200>; in device tree did not use for setting baudrate under driver probe.

0 Bin Liu over 4 years ago in reply to Thinh Nguyen

TI__Guru**** 177981 points

Hi Thinh,

current-speed doesn't set the baud rate for all cases. Please see the kernel Documentation/devicetree/bindings/serial/serial.yaml for the explanation of current-speed.

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AM6442: Issue on UART3