PROCESSOR-SDK-J721E: How to use uart3(serial@2830000) in 8.0 sdk?

Here is our uart DTS config:

main_uart3_pins_default: main_uart3_pins_default {
pinctrl-single,pins = <
J721E_IOPAD(0x78, PIN_INPUT, 14) /* (Y23) PRG1_PRU1_GPO8.UART3_RXD */
J721E_IOPAD(0x74, PIN_OUTPUT, 14) /* (AC21) PRG1_PRU1_GPO7.UART3_TXD */
>;
};

&main_uart3 {
status = "okay";
pinctrl-names = "default";
pinctrl-0 = <&main_uart3_pins_default>;
};

main_uart3: serial@2830000 {
compatible = "ti,j721e-uart", "ti,am654-uart";
reg = <0x00 0x02830000 0x00 0x100>;
reg-shift = <2>;
reg-io-width = <4>;
interrupts = <GIC_SPI 195 IRQ_TYPE_LEVEL_HIGH>;
clock-frequency = <48000000>;
current-speed = <115200>;
power-domains = <&k3_pds 280 TI_SCI_PD_EXCLUSIVE>;
clocks = <&k3_clks 280 0>;
clock-names = "fclk";
};

[ 4.336842] 40a00000.serial: ttyS1 at MMIO 0x40a00000 (irq = 15, base_baud = 6000000) is a 8250
[ 4.346192] 2800000.serial: ttyS2 at MMIO 0x2800000 (irq = 30, base_baud = 3000000) is a 8250
[ 4.354938] printk: console [ttyS2] enabled
[ 4.373794] 2810000.serial: ttyS3 at MMIO 0x2810000 (irq = 31, base_baud = 3000000) is a 8250
[ 4.382741] 2830000.serial: ttyS5 at MMIO 0x2830000 (irq = 32, base_baud = 3000000) is a 8250
[ 4.391682] 2840000.serial: ttyS6 at MMIO 0x2840000 (irq = 33, base_baud = 3000000) is a 8250

This is my tty start up log

By the way,we try to use vfs_read,vfs_write in kernel  to use uart3.

But no data output.

And we found that there are some change between 7.3 and 8.0 in tty_io.c.(Is this  kernel verison update change? )

Kernel use read_iter write_iter function instead of read and write.

May be lead to this issue?

This is a custom board

Also what is your final goal?  ---- We use uart3 to control Max96745

Based on the above the pin muxing needs to be changed  -----  pinmux we have change to mode 14 (as same as TI pinmux tool)

Could you show us a correct pinmux config for uart3?