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    SubjectRe: commit 7e92b4fc34 - x86, serial: convert legacy COM ports to platform devices - broke my serial console
    On Wed, 25 Jul 2007 15:32:53 +0200 Sébastien Dugué <sebastien.dugue@bull.net> wrote:

    >
    > 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.

    But I also need to change my inittab. At least it confirms the
    root cause of the problem.

    Sébastien.
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