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Subject[PATCH v4 0/3] serial: 8250_dw: add fractional divisor support
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 introduces necessary hooks to 8250 core.
patch2 exports serial8250_do_set_divisor()
patch3 implements the fractional divisor support for Synopsys DW 8250.

Since v3:
- simplify the dw8250_get_divisor() implementation again.

Since v2:
- rebase to tty-next branch, since I need one patch from Andy which
is in tty-next
- drop the patch "serial: 8250: let serial8250_get_divisor() get
uart_port * as param" since it's in tty-next now.
- add a new patch to export serial8250_do_set_divisor(), and reuse it
to complete dw8250_set_divisor().
- remove DW 8250 version check, since the DLF register always exists
and if fractional divisor isn't supported, the register read as 0
- add comments to explain how dw8250_get_divisor() get quot and frac.
- the frac calcuation is simplified with well implemented GENMASK
- Add Andy's Reviewed-by tag to patch1.

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: introduce get_divisor() and set_divisor() hook
serial: 8250: export serial8250_do_set_divisor()
serial: 8250_dw: add fractional divisor support

drivers/tty/serial/8250/8250_core.c | 4 +++
drivers/tty/serial/8250/8250_dw.c | 45 +++++++++++++++++++++++++++++
drivers/tty/serial/8250/8250_port.c | 30 +++++++++++++++----
include/linux/serial_8250.h | 3 ++
include/linux/serial_core.h | 7 +++++
5 files changed, 84 insertions(+), 5 deletions(-)


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