linux compile for enable uart2 - linux

Question

I am using openwrt, initially, under /dev, there is only ttyO0 with is serial port for console. and I am using it to connect the board(siamilar to beaglebone black).
Now, I am wire a gps to uart2. but I think somehow the openwrt is not enable it by default.
I checked the device tree, am335x-bone.dts(I am using bone for my board, cause my board is not BBB). I not too much setting in it. most of config is from am33xx.dtst and am335x-bone-common.dtsi.
I check the am33xx dtsi, there are some code like this under the ocp{}
uart0: serial#44e09000 {
compatible = "ti,omap3-uart";
ti,hwmods = "uart1";
clock-frequency = <48000000>;
reg = <0x44e09000 0x2000>;
interrupts = <72>;
status = "disabled";
};
uart1: serial#48022000 {
compatible = "ti,omap3-uart";
ti,hwmods = "uart2";
clock-frequency = <48000000>;
reg = <0x48022000 0x2000>;
interrupts = <73>;
status = "disabled";
};
uart2: serial#48024000 {
compatible = "ti,omap3-uart";
ti,hwmods = "uart3";
clock-frequency = <48000000>;
reg = <0x48024000 0x2000>;
interrupts = <74>;
status = "disabled";
};
uart3: serial#481a6000 {
compatible = "ti,omap3-uart";
ti,hwmods = "uart4";
clock-frequency = <48000000>;
reg = <0x481a6000 0x2000>;
interrupts = <44>;
status = "disabled";
};
uart4: serial#481a8000 {
compatible = "ti,omap3-uart";
ti,hwmods = "uart5";
clock-frequency = <48000000>;
reg = <0x481a8000 0x2000>;
interrupts = <45>;
status = "disabled";
};
uart5: serial#481aa000 {
compatible = "ti,omap3-uart";
ti,hwmods = "uart6";
clock-frequency = <48000000>;
reg = <0x481aa000 0x2000>;
interrupts = <46>;
status = "disabled";
};
I did change uart2 from disabled status to "okay" and also change code in am335x-bone-common.dtsi undert &am33xx_pinmux{}
uart0_pins: pinmux_uart0_pins {
pinctrl-single,pins = <
0x170 (PIN_INPUT_PULLUP | MUX_MODE0) /* uart0_rxd.uart0_rxd */
0x174 (PIN_OUTPUT_PULLDOWN | MUX_MODE0) /* uart0_txd.uart0_txd */
>;
};
uart2_pins: pinmux_uart2_pins {
pinctrl-single,pins = <
0x150 (PIN_INPUT_PULLUP | MUX_MODE0) /* uart0_rxd.uart0_rxd */
0x154 (PIN_OUTPUT_PULLDOWN | MUX_MODE0) /* uart0_txd.uart0_txd */
>;
};
uart0 part is default there, I add code for uart2 part below it.
and in am335x-bone.dts, I add this code to enable uart2
&uart2 {
pinctrl-names = "default";
pinctrl-0 = <&uart0_pins>;
status = "okay";
};
after compile this, I can see the /dev/ttyO2 shows up in openwrt. but when I use script write to this port and then read from it. nothing shows up.
this is my script I use lua since it's build-in
local clock = os.clock
function wait(n) -- seconds
local t0 = clock()
while clock() - t0 <= n do end
end
while true do
print("Writing")
wuar0 = io.open("/dev/ttyO0","w")
wuar1 = io.open("/dev/ttyO1","w")
wuar2 = io.open("/dev/ttyO2","w")
wuar0:write("This is uart0 \n")
wuar1:write("This is uart1 \n")
wuar2:write("This is uart2 \n")
wuar0:flush()
wuar1:flush()
wuar2:flush()
wuar0 = io.close()
wuar1 = io.close()
wuar2 = io.close()
wait(2)
print("Reading")
ruar0 = io.open("/dev/ttyO0","r")
ruar1 = io.open("/dev/ttyO1","r")
ruar2 = io.open("/dev/ttyO2","r")
print(ruar0:read())
print(ruar1:read())
print(ruar2:read())
ruar0:flush()
ruar1:flush()
ruar2:flush()
ruar0 = io.close()
ruar1 = io.close()
ruar2 = io.close()
wait(2)
end
Did I do it right? if not, what I need to do to enable the uart2.
I did a lot research, but most of them are out of update. not work in my case.
or if anyone could tell me what is the step to enable this or how I can check if it is enable or not.
any information would help a lot. Thanks.