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

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Date:	Sat, 11 Nov 2006 15:30:05 +0000
From:	Russell King <rmk+lkml@....linux.org.uk>
To:	Marc Haber <mh+linux-kernel@...schlus.de>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: ttyS0 not working any more, LSR safety check engaged

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.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 Serial core
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