Re: [PATCH] serial: 8250_dw: preserve BUSY-safe fractional divisor programming

[sashiko-bot@kernel.org]

> dw8250_probe() installs a divisor setter that makes the UART idle and
> checks DLAB before writing DLL and DLH. When dw8250_setup_port() detects
> fractional-divisor support, it replaces that setter with the library's
> callback. The replacement writes DLF and uses serial8250_do_set_divisor(),
> bypassing the divisor setter's idle sequence and DLAB readback.
> 
> If the LCR update fails to set DLAB, the subsequent divisor writes can
> reach TX and IER instead of DLL and DLH.
> 
> Install the BUSY-safe setter after hardware discovery and extend it to
> write DLF when fractional divisors are supported. Program both divisor
> fields only after DLAB has been confirmed, retaining the fractional
> divisor calculation selected by dw8250_setup_port().
> 
> Fixes: a7b9ce39fbe4 ("serial: 8250_dw: Ensure BUSY is deasserted")
> Cc: stable@vger.kernel.org
> Signed-off-by: James Hilliard <james.hilliard1@gmail.com>

Sashiko has reviewed this patch and found no issues.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261023-submit-serial-8250-dw-divisor-v1-v1-1-f452d4bb1b1f@gmail.com?part=1