Messages in this thread | | | Date | Wed, 25 Jul 2007 15:32:53 +0200 | From | Sébastien Dugué <> | Subject | Re: commit 7e92b4fc34 - x86, serial: convert legacy COM ports to platform devices - broke my serial console |
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Hi Bjorn,
On Wed, 25 Jul 2007 07:16:44 -0600 Bjorn Helgaas <bjorn.helgaas@hp.com> wrote:
> On Wednesday 25 July 2007 01:45:54 am Sébastien Dugué wrote: > > looks like the commit was dropped, nevertheless here is some more info > > to try and understand what may be going on so it may benefit the posterity ;-) > > Thank you very much. > > Your machine does indeed describe both UARTs in ACPI, and the PNP probe > finds them correctly. The only wrinkle is that the PNP probe names the > ports in the order they appear in the ACPI namespace, and your firmware > has them "backwards": > > Device (COMB) > { > Name (_HID, EisaId ("PNP0501")) > Name (_DDN, "COM2") > Name (_UID, 0x02) > > Device (COMA) > { > Name (_HID, EisaId ("PNP0501")) > Name (_DDN, "COM1") > Name (_UID, 0x01)
Yes, that's what I thought was weird in the DSDT, but thought the PnP layer would map those devices according to UID or at least DDN. It seems that's not the case.
> > There's nothing illegal about this, but with the current PNPACPI, > it causes the names to be reversed. The blind probe tries 0x3f8 > first, and names that ttyS0. But the PNP probe, using the namespace > order, finds the "COM2" port at 0x2f8 first: > > 00:0b: ttyS0 at I/O 0x2f8 (irq = 3) is a 16550A > 00:0c: ttyS1 at I/O 0x3f8 (irq = 4) is a 16550A
Oh I see, didn't notice this though.
> > So I think your serial console would work without "legacy_serial.force" > if you used "console=ttyS1" instead of "console=ttyS0". But you > shouldn't have to do that, of course.
Will try ttyS1 just to confirm...
Waiting for reboot...
OK boots fine with the serial console fully operational again.
> > The _DDN is a "DOS device name", and the _UID is a "logical device ID > that does not change across reboots." Both are optional, and PNPACPI > ignores them. But maybe we could change PNPACPI to sort by them if > they are present. I'll think about this a bit.
That would be nice, but I wish you good luck with all those crappy BIOSes out there.
Thanks,
Sébastien.
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