Re: [PATCH v2 1/4] serial: 8250_dw: Keep the BUSY-safe divisor hook when DLF is present

[Vinicius Pedrosa <vinicius.eduardo.pedrosa@gmail.com>]

Hi Andy,

On Wed, 21 Oct 2026, Andy Shevchenko wrote:

> No, just pass that as a 'bool autoconf' to it, and assign those callbacks
> there, while calling dw8250_setup_port() unconditionally from _probe().

I think the autoconf approach works for Octeon as long as everything
dw8250_setup_port() probes today stays under it, including the RS485
detection and UART_CAP_NOTEMT, not just DLF/CPR. With autoconf=false it
would only install the common divisor setter.

> I think it would be less flexible, also it will add an additional branch
> (actually two) each time the set_divisor is called (not that it's critical
> but just wanted to mentioned that).

The idle callbacks have to come from the drivers, since the
dw8250_idle_*() functions are static in 8250_dw.c. Stubs for LPSS are
fine with me.

> I dunno, I prefer just a longer solution, but I don't know how big this issue
> is that we need to backport in that way (and not taking the whole series as a
> fix).

On the severity: the IER restore comes from a7b9ce39fbe4. On the A733 I
saw hardware IER left at 0 and the console stop taking TX/RX
interrupts. I haven't tested this on hardware with a real DLF.

Given that, how about keeping the small fix as patch 1 with the stable
tag, and putting the refactoring after it in the same series? That would
keep the fix independently backportable if needed, while mainline would
still end up with the structure you proposed.

> I have Intel Galileo board that uses 8250_lpss.

The Galileo should be useful for checking the LPSS path.

Thanks,
Vinicius