linux-kernel - Re: console issue since 3.6, console=ttyS1 hangs

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Date:   Wed, 19 Oct 2016 10:07:19 +0100
From:   Sean Young <sean@...s.org>
To:     Nathan Zimmer <nzimmer@....com>
Cc:     linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
        gregkh@...uxfoundation.org, alan@...ux.intel.com
Subject: Re: console issue since 3.6, console=ttyS1 hangs

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:
> > > 3.7.0
> > > cat /sys/bus/pnp/drivers/serial/*/resources
> > > state = active
> > > io 0x2f8-0x2ff
> > > irq 12
> > > dma disabled
> > > 
> > > 3.6.0
> > > :~ # 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:
> > 
> > setserial
> > /dev/ttyS1, UART: 16550A, Port: 0x02f8, IRQ: 3
> > 
> > becomes in 3.7.0:
> > 
> > setserial
> > /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.


Sean