For Synopsys DesignWare 8250 uart which version >= 4.00a, there's a valid divisor latch fraction register. The fractional divisor width is 4bits ~ 6bits.
patch1 lets serial8250_get_divisor() get uart_port * as param patch2 introduces necessary hooks to 8250 core. patch3 implements the fractional divisor support for Synopsys DW 8250. Since v1: - add an extra patch to let serial8250_get_divisor() get uart_port * as param - take Andy's suggestions to "integrates hooks in the same way like it's done for the rest of 8250 ones". Many thanks to Andy. Jisheng Zhang (3): serial: 8250: let serial8250_get_divisor() get uart_port * as param serial: 8250: introduce get_divisor() and set_divisor() hook serial: 8250_dw: add fractional divisor support drivers/tty/serial/8250/8250_core.c | 4 +++ drivers/tty/serial/8250/8250_dw.c | 53 +++++++++++++++++++++++++++++ drivers/tty/serial/8250/8250_port.c | 33 ++++++++++++++---- include/linux/serial_core.h | 7 ++++ 4 files changed, 90 insertions(+), 7 deletions(-) -- 2.18.0
