linux-kernel - Re: How to access serial port that is set in BIOS as OS Controlled

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Message-ID: <Pine.LNX.4.64.1108111657190.12436@boston.corp.fedex.com>
Date:	Thu, 11 Aug 2011 17:07:42 +0800 (SGT)
From:	Jeff Chua <jeff.chua.linux@...il.com>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
cc:	Andrey Panin <pazke@...trinvest.ru>,
	lkml <linux-kernel@...r.kernel.org>,
	Matthew Garrett <mjg@...hat.com>
Subject: Re: How to access serial port that is set in BIOS as OS Controlled



On Thu, Aug 11, 2011 at 12:46 AM, Bjorn Helgaas <bhelgaas@...gle.com> 
wrote:
> On Fri, Aug 5, 2011 at 7:02 PM, Jeff Chua <jeff.chua.linux@...il.com> 
wrote:
> Ping, just a reminder :)
> I'm pretty sure Linux only runs _SRS when we actually *change* 
> something, which doesn't seem to follow the intent of the spec.  So if
> we can get a little more evidence here, I think it'd be worth changing
> Linux to call _SRS for every device when it enumerates it.


Sorry, it too so long. Had to work on another project.

I did some test and it seems "auto" didn't enable the port. With "auto", 
dmesg showed more info (io 0x3e8-0x3ef irq 6), but port still disabled.

After "activate", then the port can be used.

After "disabled", the port cannot be activated again.

I've attached the DSDT.dat.dsl. I've reconfigured the kernel with 
CONFIG_PNP_DEBUG_MESSAGES=y, booting with "pnp.debug", but there were not 
a lot of messages in dmesg. I've captured those below, and attached the 
dmesg as well.

Thanks,
Jeff




#  lspnp
00:00 PNP0a03 (unknown)
00:01 PNP0c02 (unknown)
00:02 PNP0c02 (unknown)
00:03 PNP0200 (unknown)
00:04 PNP0c04 (unknown)
00:05 PNP0b00 (unknown)
00:06 PNP0800 (unknown)
00:07 PNP0303 (unknown)
00:08 PNP0501 (unknown)
00:09 PNP0501 (unknown)
00:0a PNP4972 (unknown)
00:0b PNP0501 (unknown)



# cat /sys/bus/pnp/devices/00:0a/resources
state = disabled

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

# dmesg
pnp 00:0a: [io  0x03e8-0x03ef]
pnp 00:0a: [irq 6]

# cat /sys/bus/pnp/devices/00:0a/resources
state = disabled
io 0x3e8-0x3ef
irq 6

# setserial /dev/ttyS2 uart 16550a irq 6
ttyS2: LSR safety check engaged!
ttyS2: LSR safety check engaged!


# echo activate > /sys/bus/pnp/devices/00:0a/resources

# dmesg
pnp 00:0a: [io  0x03e8-0x03ef]
pnp 00:0a: [irq 6]
pnp 00:0a: activated

# cat /sys/bus/pnp/devices/00:0a/resources
state = active
io 0x3e8-0x3ef
irq 6


# echo disable > /sys/bus/pnp/devices/00:0a/resources

# dmesg
pnp 00:0a: disabled

# cat /sys/bus/pnp/devices/00:0a/resources
state = disabled


# echo activate > /sys/bus/pnp/devices/00:0a/resources
-bash: echo: write error: Device or resource busy

# dmesg
pnp 00:0a: unable to assign resources




Thanks,
Jeff
View attachment "DSDT.dat.dsl" of type "TEXT/PLAIN" (106435 bytes)

View attachment "dmesg" of type "TEXT/PLAIN" (22770 bytes)