Changing UART Baudrate to 115200

csagin · December 4, 2018, 2:52pm

Hello

I want to change UART baudrate from 1500000 to 115200, how can i do that? I try to update U-Boot setting “CONFIG_BAUDRATE” in evb-rk3399_defconfig file.

Thanks for your help and support

Loic · December 4, 2018, 6:18pm

One solution is to update the device tree node:

github.com

96rocks/kernel/blob/332d9a61dcfce0315d220b961aaa9f834faa28b4/arch/arm64/boot/dts/rockchip/rock960-model-ab-linux.dts#L63

    
      
          
          
	model = "ROCK960 - 96boards based on Rockchip RK3399";
          	compatible = "rockchip,rock960","rockchip,rk3399";
          
          
	fiq_debugger: fiq-debugger {
          		compatible = "rockchip,fiq-debugger";
          		rockchip,serial-id = <2>;
          		rockchip,signal-irq = <182>;
          		rockchip,wake-irq = <0>;
          		rockchip,irq-mode-enable = <1>;  /* If enable uart uses irq instead of fiq */
          		rockchip,baudrate = <1500000>;  /* Only 115200 and 1500000 */
          		pinctrl-names = "default";
          		pinctrl-0 = <&uart2c_xfer>;
          	};
          
          
	vcc1v8_s0: vcc1v8-s0 {
          		compatible = "regulator-fixed";
          		regulator-name = "vcc1v8_s0";
          		regulator-min-microvolt = <1800000>;
          		regulator-max-microvolt = <1800000>;
          		regulator-always-on;

csagin · December 10, 2018, 10:28am

Thanks a lot. It worked on my setup.

abhimanyu_PP · April 12, 2021, 7:46am

Hi @Loic,

I tried this change on Rock960c board. But the changes do not seem to take effect. I still get output at baud 1500000.

Also, I tried your suggesion at "getty: bad speed: 1500000" Error - #3 by csagin, by changing extconf at ./build/extlinux/rk3399.conf to the following.

console=ttyFIQ0,115200n8 .

The complete file looks like below

label kernel-4.4
    kernel /Image
    fdt /rock960-model-c-linux.dtb
    append earlycon=uart8250,mmio32,0xff1a0000 swiotlb=1 coherent_pool=1m earlyprintk console=ttyFIQ0,115200n8 rw root=PARTUUID=b921b045-1d rootfstype=ext4 init=/sbin/init rootwait

Could you please suggest?