Re: [PATCH v2 0/2] serial: 8250: loongson: Add support for MIPS-based Loongson 3A4000

[Jiaxun Yang]

On Sun, 15 Mar 2026, at 6:42 PM, Rong Zhang wrote:
> This series targets the serial tree.
>
> The UART controller on Loongson 3A4000 is compatible with Loongson
> 2K1500, which is NS16550A-compatible with an additional fractional
> frequency divisor register.
>
> Patch 1 adds loongson,ls3a4000-uart as compatible with
> loongson,ls2k1500-uart.
>
> Patch 2 enables building 8250_loongson (loongson-uart) on MIPS
> Loongson64.
>
> Tested on Loongson-LS3A4000-7A1000-NUC-SE with a 25MHz UART clock.
> Without fractional frequency divisor, the actual baud rate was 111607
> (25MHz / 16 / 14, measured value: 111545) and some USB-to-UART
> converters couldn't work with it at all. With fractional frequency
> divisor, the measured baud rate becomes 115207, which is quite accurate.
>
> The patch for the MIPS tree to update the compatible strings in the
> loongson64g-package DTS is sent separately, as it's independant of this
> series and can be applied in any order (the compatible strings there
> still contain "ns16550a", so no regression will be introduced).
>
> Changes in v2:
> - Separated from v1 (patch 1,2): 
> https://lore.kernel.org/r/20260314234143.651298-1-rongrong@xxxxxxxxxxxxxxxxx/
> (thanks Krzysztof Kozlowski)

For the series:

Reviewed-by: Jiaxun Yang <jiaxun.yang@xxxxxxxxxxx>

Thanks!

>
> Rong Zhang (2):
>   dt-bindings: serial: 8250: Add Loongson 3A4000 uart compatible
>   serial: 8250: loongson: Enable building on MIPS Loongson64
>
>  Documentation/devicetree/bindings/serial/8250.yaml | 1 +
>  drivers/tty/serial/8250/Kconfig                    | 9 +++++----
>  2 files changed, 6 insertions(+), 4 deletions(-)
>
>
> base-commit: 267594792a71018788af69e836c52e34bb8054af
> -- 
> 2.53.0

-- 
- Jiaxun