Re: console issue since 3.6, console=ttyS1 hangs

From: Nathan Zimmer
Date: Wed Oct 19 2016 - 18:14:18 EST

On 10/19/2016 04:07 AM, Sean Young wrote:
On Tue, Oct 18, 2016 at 02:29:30PM -0500, Nathan Zimmer wrote:
On Tue, Oct 18, 2016 at 07:05:18PM +0100, Sean Young wrote:
On Tue, Oct 18, 2016 at 11:40:04AM -0500, Nathan Zimmer wrote:
cat /sys/bus/pnp/drivers/serial/*/resources
state = active
io 0x2f8-0x2ff
irq 12
dma disabled

:~ # cat /sys/bus/pnp/drivers/serial/*/resources
cat: /sys/bus/pnp/drivers/serial/*/resources: No such file or directory
irq 12 for ttyS1? That should be irq 3. The bios is putting bogus information
in pnp. Maybe there is rubbish in the bios setup or maybe it's fixed in a
newer bios update.

So before this change, the kernel would assume irq 3. After this change,
the kernel first uses the information in pnp to see where the serial
port is. It gets told that it's irq 12 and presumably it runs into all
sorts of problems then. If memory serves that's the irq for the ps/2 mouse.

The interesting bit is in 3.6.0:

/dev/ttyS1, UART: 16550A, Port: 0x02f8, IRQ: 3

becomes in 3.7.0:

/dev/ttyS1, UART: 16550A, Port: 0x02f8, IRQ: 12

You should be able to set the right irq with setserial, but obviously
that doesn't help you if it fails in early boot. It's not immediately
obvious to me what can be done in the kernel for this. Maybe the dmesg
output could inspire, thanks.
Yea the changing irq seemed weird to me too but I couldn't manage a guess to why.

Here are the dmesgs.
So with 3.6.0:

[ 2.079980] Serial: 8250/16550 driver, 8 ports, IRQ sharing disabled
[ 2.100887] serial8250: ttyS1 at I/O 0x2f8 (irq = 3) is a 16550A
[ 2.101715] serial 00:04: unable to assign resources
[ 2.102174] serial: probe of 00:04 failed with error -16
The pnp probe fails for some reason. I don't understand why.

With 3.7.0:

[ 2.062700] Serial: 8250/16550 driver, 8 ports, IRQ sharing disabled
[ 2.063250] serial 00:04: [io 0x02f8-0x02ff]
[ 2.063875] serial 00:04: [irq 12]
[ 2.064345] serial 00:04: [dma 18446744073709551615 disabled]
[ 2.065540] serial 00:04: activated
[ 2.086442] 00:04: ttyS1 at I/O 0x2f8 (irq = 12) is a 16550A
Now the pnp probe succeeds (with broken irq from pnp).

Can you please check if there is a wrong irq configured in the bios setup
or if there is a bios update available? I don't know why this worked in
the first place.


Apparently this is the latest bios available for these nodes.
Also in the bios setup screens I don't see anything for changing irq numbers for serial console.
But this is a cluster so sometimes thing get hidden to keep everything uniform as possible.

If you want to point me to the pnp probe code you would be suspicious of I can try to debug and see what is going there.