Re: git: 1491fe8f864a - main - uart/pci: support 16550A PCI serial devices

On Fri, Mar 27, 2026 at 08:33:37AM +0000, Roger Pau Monné wrote:
> The branch main has been updated by royger:
> 
> URL: https://cgit.FreeBSD.org/src/commit/?id=1491fe8f864af5af37e83f1d12459905fb6097fd
> 
> commit 1491fe8f864af5af37e83f1d12459905fb6097fd
> Author:     Roger Pau Monné <royger@FreeBSD.org>
> AuthorDate: 2026-03-26 10:01:57 +0000
> Commit:     Roger Pau Monné <royger@FreeBSD.org>
> CommitDate: 2026-03-27 08:26:32 +0000
> 
>     uart/pci: support 16550A PCI serial devices
>     
>     Expand the current check to also attach the ns8250 driver to devices
>     reporting as 16550A.  This has been tested to work on a real device.
>     
>     From an inspection of the code in the ns8250 driver it seems like it should
>     support up to 16950A devices, but I don't have hardware to ensure that,
>     hence be conservative with the change.

I have a system which hangs in uart_bus_probe() after this change.  It
has a 2-port UART PCI card installed:

puc0@pci0:6:0:0:        class=0x070002 rev=0x00 hdr=0x00 vendor=0x1415 device=0xc158 subvendor=0x1415 subdevice=0xc158
    vendor     = 'Oxford Semiconductor Ltd'
    device     = 'OXPCIe952 Dual Native 950 UART'
    class      = simple comms
    subclass   = UART

Normally puc(4) attaches to it and creates two child uart devices:

    puc0
	Interrupt request lines:
	    0x11
	pcib7 memory window:
	    0x84000000-0x841fffff
	    0x84200000-0x843fffff
	    0x84400000-0x84403fff
      uart2
	  puc0 I/O memory mapping:
	      0x84401000-0x844011ff
	  puc0 port numbers:
	      0x1
      uart3
	  puc0 I/O memory mapping:
	      0x84401200-0x844013ff
	  puc0 port numbers:
	      0x2

After this change, though, uart(4) tries to probe the device directly
and hangs.  Presumably we still want to exclude at least multi-port
devices here?

>     MFC: 2 weeks
>     Reviewed by: imp
>     Differential revision: https://reviews.freebsd.org/D56095
> ---
>  sys/dev/uart/uart_bus_pci.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/sys/dev/uart/uart_bus_pci.c b/sys/dev/uart/uart_bus_pci.c
> index 22af8ee8663c..7087958cbfa9 100644
> --- a/sys/dev/uart/uart_bus_pci.c
> +++ b/sys/dev/uart/uart_bus_pci.c
> @@ -297,7 +297,7 @@ uart_pci_probe(device_t dev)
>  	}
>  	if (pci_get_class(dev) == PCIC_SIMPLECOMM &&
>  	    pci_get_subclass(dev) == PCIS_SIMPLECOMM_UART &&
> -	    pci_get_progif(dev) < PCIP_SIMPLECOMM_UART_16550A) {
> +	    pci_get_progif(dev) <= PCIP_SIMPLECOMM_UART_16550A) {
>  		/* XXX rclk what to do */
>  		id = &cid;
>  		sc->sc_class = &uart_ns8250_class;
>