[PATCH 0/3] MIPS: dts: loongson64g-package: Switch to Loongson UART driver

[Rong Zhang]

Loongson64g is Loongson 3A4000, whose UART controller 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.

Patch 3 updates 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.

Rong Zhang (3):
  dt-bindings: serial: 8250: Add Loongson 3A4000 uart compatible
  serial: 8250: loongson: Enable building on MIPS Loongson64
  MIPS: dts: loongson64g-package: Switch to Loongson UART driver

 Documentation/devicetree/bindings/serial/8250.yaml   | 1 +
 arch/mips/boot/dts/loongson/loongson64g-package.dtsi | 4 ++--
 drivers/tty/serial/8250/Kconfig                      | 9 +++++----
 3 files changed, 8 insertions(+), 6 deletions(-)


base-commit: 69237f8c1f69112cca7388af7fab6d0ee45a2525
-- 
2.53.0