Re: ttyS0 not working any more, LSR safety check engaged

[Andrew Morton <akpm@osdl.org>]

On Sat, 11 Nov 2006 15:30:05 +0000
Russell King <rmk+lkml@arm.linux.org.uk> wrote:

> On Sat, Nov 11, 2006 at 01:34:55PM +0100, Marc Haber wrote:
> > On Sat, Nov 11, 2006 at 11:50:16AM +0000, Russell King wrote:
> > > Maybe something to do with PNP?  Maybe ACPI?  Both of those I know
> > > nothing about, but I suggest that if you have PNP enabled, you
> > > build and use the 8250_pnp module, even if your port is detected
> > > by the legacy detection methods in 8250.
> > 
> > How do I configure that?
> > 
> > I have:
> >   ? ?<*> 8250/16550 and compatible serial support                         ? ?
> >   ? ?[*]   Console on 8250/16550 and compatible serial port               ? ?
> >   ? ?<*>   8250/16550 PCI device support                                  ? ?
> >   ? ?<*>   8250/16550 PNP device support                                  ? ?
> 
> That's fine.
> 
> > $ grep -i 'nov 11.*\(8250\|serial\|ttyS\|pnp\)' /var/log/syslog/syslog
> > pnp: PnP ACPI init
> > pnp: PnP ACPI: found 15 devices
> > PnPBIOS: Disabled by ACPI PNP
> > pnp: 00:0d: ioport range 0x4d0-0x4d1 has been reserved
> > pnp: 00:0d: ioport range 0x1000-0x107f could not be reserved
> > pnp: 00:0d: ioport range 0x1100-0x113f has been reserved
> > pnp: 00:0d: ioport range 0x1200-0x121f has been reserved
> > isapnp: Scanning for PnP cards...
> > isapnp: No Plug & Play device found
> > Serial: 8250/16550 driver $Revision: 1.90 $ 4 ports, IRQ sharing disabled
> > serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
> 
> ttyS0 detected via legacy ISA probes.
> 
> > serial8250: ttyS2 at I/O 0x3e8 (irq = 4) is a 16550A
> 
> ttyS2 detected via legacy ISA probes.
> 
> > 00:02: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
> 
> ttyS0 detected via PNP device 00:02.
> 
> > ttyS0: LSR safety check engaged!
> > ttyS2: LSR safety check engaged!
> 
> and then it mysteriously disappears on us.
> 
> It's certainly a mystery.  Suggest you git bisect to find the offending
> change - I doubt it'll be serial/8250 itself.

/proc/ioports and /proc/iomem might contain hints - can we see those please?