Re: [PATCH 1/2] dt-bindings: serial: 8250: add Microchip Core16550

[Kohei Otsuka]

On Tue, Nov 10, 2026 at 6:35 AM Conor Dooley <conor@xxxxxxxxxx> wrote:
>
> On Mon, Nov 09, 2026 at 01:54:17PM +1100, Kohei Otsuka wrote:
> > On Thu, Nov 5, 2026 at 3:20 AM Conor Dooley <conor@xxxxxxxxxx> wrote:
> > >
> > > On Tue, Nov 03, 2026 at 11:11:31AM +1100, Kohei Otsuka wrote:
> > > > Core16550 is a 16550-compatible UART soft IP core for Microchip FPGAs,
> > > > including the fabric of PolarFire SoC. Its registers follow the 16550A,
> > > > so ns16550a stays the fallback, but
> > >
> > > > it raises no interrupt on TEMT,
> > > > which the driver has to know about to support RS-485 on it.
> > >
> > > Doesn't this exclude using the fallback to ns16550a, since it requires
> > > specific interrupt handling?
> > >
> > Everything a plain ns16550a driver does works on
> > Core16550 including transmit, receive, FIFOs, modem control and the baud rate
> > divisor. The only thing that needs the specific compatible string is
> > software RS-485
> > (em485), which waits for a TEMT interrupt the core doesn’t raise.
> > Without the patch, RS-485 direction control is missing, but the UART
> > otherwise works. If you’d rather
> > not have the fallback, I can match the compatible in 8250_of directly.
>
> In my opinion, this is enough to invalidate the ns16550a fallback.


Thanks, v3 drops the fallback and matches the compatible in 8250_of.

-- 


Kohei Otsuka
Satellite Flight Software Team Lead

  koheio@xxxxxxxxxxxxxxxxx   spacemachines.com

 UTS Tech Lab, 36-38 Lord Street, Botany NSW 2019