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JeffyCN / meta-rockchip

Yocto BSP layer for the Rockchip SOC boards
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What is the best way to enable uart? #83

Closed yrik closed 10 months ago

yrik commented 10 months ago

I'm building the project where I want to use uart/serial for communication with an external device. I have two options. Either to free the default uart from system communications (linux is using this serial to show boot logs) or to enable another uart. Is it possible to configure it on yocto level? Are there any configuration variables I could use?

I see there is SERIAL_CONSOLES defined in this repo, would it help if I redefine it? Or is there a way to edit bootargs? What is the best way to include a custom device tree overlay like the one mentioned here https://forum.radxa.com/t/enable-serial-port-uart2/15467?

JeffyCN commented 10 months ago

it's easy to enable uart in kernel dts, something like

&uartx {
status="okay"
};

so you might need to: 1/ use git clone to download the kernel source 2/ modify your kernel dts and git commit it 3/ set the kernel to use this local source(follow the readme.md of this repo's last section)

yrik commented 10 months ago

Thank you for the answer. I was looking for a way to do it on the level of yocto configuration. For example, for meta-raspberrypi I can do the following settings in conf/machine/rpi4.conf:

 # prevent using serial for linux output
CMDLINE_SERIAL = ""
 # modify boot commands
CMDLINE:append = "..."
 # modify device overlays 
RPI_KERNEL_DEVICETREE_OVERLAYS:append = "overlays/tc358743-overlay.dtbo"

In ideal case, I would need to have way to directly use https://github.com/radxa/overlays/blob/main/arch/arm64/boot/dts/rockchip/overlays/rk3588-uart3-m1.dts