rk3399修改调试串口

rk3399可以修改调试串口为任意板载的uart

由于厂家的一级loader没有开源，因此更改调试串口后，一级loader的打印无法再看到了

手里面有一块rockpi4b的板子
其pin脚如下，从官方的uart改为下图中的uart4

官方支持的bsp代码

https://github.com/radxa/rockchip-bsp.git 

首先修改uboot的代码

git diff
diff --git a/arch/arm/dts/rk3399-u-boot.dtsi b/arch/arm/dts/rk3399-u-boot.dtsi
index 8000614..4c44548 100644
--- a/arch/arm/dts/rk3399-u-boot.dtsi
+++ b/arch/arm/dts/rk3399-u-boot.dtsi
@@ -11,7 +11,7 @@
        };
 };
 
-&uart2 {
+&uart4 {
        clock-frequency = <24000000>;
:...skipping...
diff --git a/arch/arm/dts/rk3399-u-boot.dtsi b/arch/arm/dts/rk3399-u-boot.dtsi
index 8000614..4c44548 100644
--- a/arch/arm/dts/rk3399-u-boot.dtsi
+++ b/arch/arm/dts/rk3399-u-boot.dtsi
@@ -11,7 +11,7 @@
        };
 };
 
-&uart2 {
+&uart4 {
        clock-frequency = <24000000>;
        u-boot,dm-pre-reloc;
        status = "okay";
diff --git a/arch/arm/dts/rockpi-4b-linux.dts b/arch/arm/dts/rockpi-4b-linux.dts
old mode 100644
new mode 100755
index f28fa8f..46a147b
--- a/arch/arm/dts/rockpi-4b-linux.dts
+++ b/arch/arm/dts/rockpi-4b-linux.dts
@@ -22,7 +22,7 @@
        };
 
        chosen {
-               stdout-path = &uart2;
+               stdout-path = &uart4;
                u-boot,spl-boot-order = &sdhci, &sdmmc;
        };
 
diff --git a/configs/rock-pi-4b-rk3399_defconfig b/configs/rock-pi-4b-rk3399_defconfig
index f0292e8..5a4b2e1 100644
--- a/configs/rock-pi-4b-rk3399_defconfig
+++ b/configs/rock-pi-4b-rk3399_defconfig
@@ -14,7 +14,7 @@ CONFIG_DEBUG_UART=y
 CONFIG_FIT=y
 CONFIG_SPL_LOAD_FIT=y
 CONFIG_SPL_FIT_GENERATOR="arch/arm/mach-rockchip/make_fit_atf.py"
-CONFIG_BOOTDELAY=1
+CONFIG_BOOTDELAY=5
 # CONFIG_DISPLAY_CPUINFO is not set
 CONFIG_ANDROID_BOOTLOADER=y
 CONFIG_SPL_STACK_R=y
@@ -71,9 +71,9 @@ CONFIG_RAM=y
 CONFIG_SPL_RAM=y
 CONFIG_DM_RESET=y
 CONFIG_BAUDRATE=1500000
-CONFIG_DEBUG_UART_BASE=0xFF1A0000
+CONFIG_DEBUG_UART_BASE=0xFF370000
 CONFIG_DEBUG_UART_CLOCK=24000000
-CONFIG_DEBUG_UART_SHIFT=2
+CONFIG_DEBUG_UART_SHIFT=4
 CONFIG_SYSRESET=y
 CONFIG_USB=y
 CONFIG_USB_XHCI_HCD=y

linux kernel更改如下

 git diff
diff --git a/arch/arm64/boot/dts/rockchip/overlays-rockpi4/hw_intfc.conf b/arch/arm64/boot/dts/rockchip/overlays-rockpi4/hw_intfc.conf
index 024fe76..41d3d48 100644
--- a/arch/arm64/boot/dts/rockchip/overlays-rockpi4/hw_intfc.conf
+++ b/arch/arm64/boot/dts/rockchip/overlays-rockpi4/hw_intfc.conf
@@ -21,7 +21,7 @@ intfc:i2c7=off
 #intfc:dtoverlay=at24c02
 
 # Serial console on UART2
-intfc:dtoverlay=console-on-ttyS2
+intfc:dtoverlay=console-on-ttyS4
 
 # Serial console on UART4
 #intfc:dtoverlay=console-on-ttyS4
diff --git a/arch/arm64/boot/dts/rockchip/rockpi-4-linux.dtsi b/arch/arm64/boot/dts/rockchip/rockpi-4-linux.dtsi
index 1a18fc4..e6ea618 100644
--- a/arch/arm64/boot/dts/rockchip/rockpi-4-linux.dtsi
+++ b/arch/arm64/boot/dts/rockchip/rockpi-4-linux.dtsi
@@ -54,13 +54,13 @@
        fiq_debugger: fiq-debugger {
                status = "disabled";
                compatible = "rockchip,fiq-debugger";
-               rockchip,serial-id = <2>;
+               rockchip,serial-id = <4>;
                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>;
+               pinctrl-0 = <&uart4_xfer>;
        };
 
        vcc1v8_s0: vcc1v8-s0 {
@@ -750,7 +750,7 @@
 };
 
 &uart4 {
-       status = "disabled";
+       status = "okay";
 };

上板子调试完全可以，只是缺少了一级loader的打印