Re: [PATCH v2] MIPS: dts: loongson64g-package: Switch to Loongson UART driver

[Thomas Bogendoerfer <tsbogend@alpha.franken.de>]

On Mon, Mar 16, 2026 at 02:44:00AM +0800, Rong Zhang wrote:
> Loongson64g is Loongson 3A4000, whose UART controller is compatible with
> Loongson 2K1500, which is NS16550A-compatible with an additional
> fractional frequency divisor register.
> 
> Update the compatible strings to reflect this, so that 3A4000 can
> benefit from the fractional frequency divisor provided by loongson-uart.
> This is required on some devices, otherwise their UART can't work at
> some high baud rates, e.g., 115200.
> 
> 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.
> 
> Signed-off-by: Rong Zhang <rongrong@oss.cipunited.com>
> ---
> This patch targets the MIPS tree.
> 
> The series for the serial tree to update dt-bindings and enable building
> 8250_loongson (loongson-uart) on MIPS Loongson64 is sent separately, as
> it's independant of this patch and can be applied in any order (the
> compatible strings here still contain "ns16550a", so no regression will
> be introduced).
> 
> Changes in v2:
> - Separated from v1 (patch 3): https://lore.kernel.org/r/20260314234143.651298-1-rongrong@oss.cipunited.com/
> (thanks Krzysztof Kozlowski)
> ---
>  arch/mips/boot/dts/loongson/loongson64g-package.dtsi | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

applied to mips-next

Thomas.

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