On Wed, 16 Nov 2022, Pavel Machek wrote:
> > From: Maciej W. Rozycki <macro@xxxxxxxxxxx>
> >
> > [ Upstream commit 9906890c89e4dbd900ed87ad3040080339a7f411 ]
> >
> > A SERIAL_8250_16550A_VARIANTS configuration option has been recently
> > defined that lets one request the 8250 driver not to probe for 16550A
> > device features so as to reduce the driver's device startup time in
> > virtual machines.
> >
> > Some actual hardware devices require these features to have been fully
> > determined however for their driver to work correctly, so define a flag
> > to let drivers request full 16550A feature probing on a device-by-device
> > basis if required regardless of the SERIAL_8250_16550A_VARIANTS option
> > setting chosen.
> >
> > Fixes: dc56ecb81a0a ("serial: 8250: Support disabling mdelay-filled probes of 16550A variants")
> > Cc: stable@xxxxxxxxxxxxxxx # v5.6+
>
> You said you'd drop this. It is still unused in 5.10.155, as flag is
> never set.
Right. Technically it fixes a problem introduced in v5.6, but it wasn't
exposed until commit 00b7a4d4ee42 ("serial: 8250: Request full 16550A
feature probing for OxSemi PCIe devices") in v5.19 (unless, of course
another UART broke that we don't know of). I agree it's OK to drop this
change in this case.
Maciej
