Bug 40612

Summary:	UART not automatically enabled
Product:	ACPI	Reporter:	Bjorn Helgaas (bjorn)
Component:	Config-Other	Assignee:	acpi_config-other
Status:	CLOSED CODE_FIX
Severity:	normal	CC:	florian, jeff.chua.linux, rui.zhang
Priority:	P1
Hardware:	All
OS:	Linux
URL:	https://lkml.org/lkml/2011/7/28/27
Kernel Version:		Subsystem:
Regression:	No	Bisected commit-id:
Attachments:	dmesg log DSDT (disassembled)

Description Bjorn Helgaas 2011-08-05 15:11:15 UTC

Jeff says:

> I'm trying to access the serial port ttyS2 that is set in the BIOS as
> "OS Controlled" without much success. If it's set it to "Always
> Enabled",  I can access the serial port.

> This is on the Intermec CV60, and ttyS2 is the touchscreen port.

> # setserial /dev/ttyS2
> /dev/ttyS2, UART: 16550A, Port: 0x03e8, IRQ: 6


> If I set the BIOS to "OS Controlled", I can't access the serial port
> no matter what parameter I pass to the setserial. The factory default
> is "OS Controlled", and Window XP can detect and access the port.

and found that this is enough to enable it:

> echo "auto" > /sys/bus/pnp/devices/00:0a/resources

My guess (with no evidence) is that running _SRS enables the device, and that Windows does that automatically but Linux doesn't.

I think it's a bug that Linux doesn't make this port work automatically.

Comment 1 Bjorn Helgaas 2011-08-11 15:40:42 UTC

Created attachment 68572 [details]
dmesg log

Comment 2 Bjorn Helgaas 2011-08-11 15:41:34 UTC

Created attachment 68582 [details]
DSDT (disassembled)

Comment 3 Florian Mickler 2011-08-29 18:41:51 UTC

A patch referencing this bug report has been merged in Linux v3.1-rc4:

commit ab8ba3a2d2cba6a658ef596cd5b2e0905b6c8a9f
Author: Bjorn Helgaas <bhelgaas@google.com>
Date:   Tue Aug 16 12:02:28 2011 -0600

    serial: 8250_pnp: add Intermec CV60 touchscreen device

Comment 4 Zhang Rui 2012-01-18 05:31:16 UTC

Hmm,
what's the status of this bug?
Does the problem still exists in the latest upstream kernel?

Comment 5 Jeff Chua 2012-01-18 09:28:16 UTC

Fixed.

commit ab8ba3a2d2cba6a658ef596cd5b2e0905b6c8a9f
Author: Bjorn Helgaas <bhelgaas@google.com>
Date:   Tue Aug 16 12:02:28 2011 -0600

    serial: 8250_pnp: add Intermec CV60 touchscreen device
    
    It would have been nice if Intermec had supplied a PNP0501 _CID for the
    COM3 device, but they didn't, so we have to recognize it explicitly.
    
    Reference: https://bugzilla.kernel.org/show_bug.cgi?id=40612
    CC: Jeff Chua <jeff.chua.linux@gmail.com>
    Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
    Cc: stable <stable@kernel.org>
    Acked-by: Alan Cox <alan@linux.intel.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

Comment 6 Zhang Rui 2012-01-19 02:03:40 UTC

Good to know.
Bug closed.