Re: [PATCH] MIPS: Loongson: Add support for serial console

From: WANG Xuerui
Date: Sat May 16 2020 - 07:09:20 EST


On 5/16/20 3:03 PM, Tiezhu Yang wrote:

After commit 87fcfa7b7fe6 ("MIPS: Loongson64: Add generic dts"),
there already exists the node and property of Loongson CPU UART0
in loongson3-package.dtsi:

cpu_uart0: serial@1fe001e0 {
compatible = "ns16550a";
reg = <0 0x1fe001e0 0x8>;
clock-frequency = <33000000>;
interrupt-parent = <&liointc>;
interrupts = <10 IRQ_TYPE_LEVEL_HIGH>;
no-loopback-test;
};

In order to support for serial console on the Loongson platform,
add CONFIG_SERIAL_OF_PLATFORM=y to loongson3_defconfig.

With this patch, we can see the following boot message:

[ 1.877745] printk: console [ttyS0] disabled
[ 1.881979] 1fe001e0.serial: ttyS0 at MMIO 0x1fe001e0 (irq = 16, base_baud = 2062500) is a 16550A
[ 1.890838] printk: console [ttyS0] enabled

And also, we can login normally from the serial console.

Signed-off-by: Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>
---

Hi Jiaxun,

Thank you very much for your suggestion.

arch/mips/configs/loongson3_defconfig | 1 +
1 file changed, 1 insertion(+)

diff --git a/arch/mips/configs/loongson3_defconfig b/arch/mips/configs/loongson3_defconfig
index 6768c16..cd95f08 100644
--- a/arch/mips/configs/loongson3_defconfig
+++ b/arch/mips/configs/loongson3_defconfig
@@ -217,6 +217,7 @@ CONFIG_SERIAL_8250_EXTENDED=y
CONFIG_SERIAL_8250_MANY_PORTS=y
CONFIG_SERIAL_8250_SHARE_IRQ=y
CONFIG_SERIAL_8250_RSA=y
+CONFIG_SERIAL_OF_PLATFORM=y
CONFIG_HW_RANDOM=y
CONFIG_RAW_DRIVER=m
CONFIG_I2C_CHARDEV=y

Hi,

The patch title is again exaggerating things. This is a defconfig change, so please refer to `git log` output of `arch/mips/configs` and use something like "MIPS: Loongson: loongson3_defconfig: enable serial console" or "MIPS: Loongson: enable serial console in defconfig". The current title reads as if Loongson kernels never were able to use a serial console in the past.