Re: [PATCH] arm64: defconfig: increase SERIAL_8250_NR_UARTS

[Nishanth Menon]

On 16:31-20231201, Arnd Bergmann wrote:
> On Fri, Dec 1, 2023, at 07:49, Nishanth Menon wrote:
> > On 08:03-20231201, Tony Lindgren wrote:
> >> * Francesco Dolcini <francesco@xxxxxxxxxx> [231130 23:17]:
> >> > Increase CONFIG_SERIAL_8250_NR_UARTS from 4 to 8, the current legacy value
> >> > is not adequate for embedded systems that use SoCs where it's common to
> >> > have a large number of serial ports.
> >> > 
> >> > No need to change CONFIG_SERIAL_8250_RUNTIME_UARTS, see commit 9d86719f8769
> >> > ("serial: 8250: Allow using ports higher than SERIAL_8250_RUNTIME_UARTS").
> >> > 
> >> > This enables using the UART connected Bluetooth device on Verdin AM62
> >> > board.
> >> 
> >> OK makes sense for distro use.
> >> 
> >> Disabling unused ports leads into port names shifting, which we still can't
> >> easily tolerate until we have the DEVNAME:0.0 style addressing available for
> >> ports. So for now we still depend CONFIG_SERIAL_8250_NR_UARTS, eventually
> >> that too should become just a legacy ISA port array.. Meanwhile:
> >> 
> >> Reviewed-by: Tony Lindgren <tony@xxxxxxxxxxx>
> >
> > I'd prefer to get Arnd's view on the topic as well (I kind of
> > recollect some historic discussion which I am not failing to trace
> > that there usage model doesn't exceed 4 and aliases could be used to
> > map these as required for the platform). The 8250 debate has been
> > popping on and off over the years.. Sigh.. memories of [1] still haunt
> > me.
> 
> I don't recall any reason to have the limit set to the default
> of 4, other than possibly using excessive amounts of .data in
> vmlinux, but we have other serial port drivers that just hardcode
> a much larger value.

Thanks Arnd, we will queue this up.

Francesco: Could you respin with a more clear commit message to indicate
actual board usage instance.

-- 
Regards,
Nishanth Menon
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