Serial changes for HP ia64 boxes (MAY BREAK YOUR CONSOLE)

From: Bjorn Helgaas <>
Date: 2004-11-06 07:47:52
This patch [1], which appeared up in 2.6.10-rc1-mm2, changes the way
serial devices are named.  This only affects machines where firmware
supplies an HCDP or PCDP table.  As far as I know, only HP has shipped
such machines.

If you have an HP machine and you're using the MP serial console port
(the connector labelled "console" on the 3-headed cable), this patch
will break your console!


 1) The console device will change from /dev/ttyS0 to /dev/ttyS1,
    ttyS2, or ttyS3, so:

    1a) Edit /etc/inittab to add a getty entry for
           /dev/ttyS1 (rx4640, rx5670, rx7620, rx8620, Superdome),
           /dev/ttyS2 (rx1600), or
           /dev/ttyS3 (rx2600).

    1b) Edit /etc/securetty to add ttyS1, ttyS2, or ttyS3.

    1c) Leave the existing ttyS0 entries in /etc/inittab and
        /etc/securetty so you can still boot old kernels.

 2) Edit /etc/elilo.conf to remove any "console=" arguments (see [2]).

 3) Run elilo to install the bootloader with new configuration.

 4) Reboot and use the EFI boot option maintenance menu to select
    exactly one device for console output, input, and standard error.
    Then do a cold reset so the changes take effect.

    For the MP console, be careful to select the device with
    "Acpi(HWP0002,700)/Pci(...)/Uart" in the path (see [3]).


  - Prior to patch [1], serial device names depended on the HCDP,
    which in turn depends on EFI console settings.  After this patch,
    the naming always stays the same, regardless of firmware settings.

    For example, an rx1600 with a single built-in serial port plus
    an MP has these ports:
                                   Old             Old
                  MMIO         (EFI console    (EFI console
                 address        on builtin)     on MP port)      New
                ----------     ------------    ------------     -----
    builtin     0xff5e0000        ttyS0           ttyS1         ttyS0
    MP UPS      0xf8031000        ttyS1           ttyS2         ttyS1
    MP Console  0xf8030000        ttyS2           ttyS0         ttyS2
    MP 2        0xf8030010        ttyS3           ttyS3         ttyS3
    MP 3        0xf8030038        ttyS4           ttyS4         ttyS4

  - If you want to have multiple devices in the EFI console path, you
    can, but Linux won't be able to deduce which console to use, so it
    will default to using VGA.  You can use "console=hcdp" (the UART
    device from the EFI path) or "console=ttyS<n>" to select the
    device directly.


  - No kernel output after "Uncompressing Linux... done":

        -> You're using an MP port as the console and specified
           "console=ttyS0".  This port is now named something else.
           Remove the "console=" option.

        -> Multiple UARTs selected as EFI console devices, and you're
           looking at the wrong one.  Make sure only one UART is
           selected (use the EFI Boot Manager "Boot option maintenance"

        -> You're physically connected to the MP port but have a
           non-MP UART selected as EFI console device.  Either move
           the console cable to the non-MP UART, or change the EFI
           console path to the MP UART (the MP UART is the one with
           "Acpi(HWP0002,700)/Pci(...)/Uart" in it.)

  - Long pause (60+ seconds) between "Uncompressing Linux... done"
    and start of kernel output:

        -> No early console, probably because you used "console=ttyS<n>".
           Remove the "console=" option.

  - Kernel and init script output works fine, but no "login:" prompt:

        -> Add getty entry to /etc/inittab for console tty.  Use the table
           in (1a) above or look for the "Adding console on ttyS<n>" message
           that tells you which device is the console.

  - "login:" prompt, but can't login as root:

        -> Add entry to /etc/securetty for console tty.


[2] When the EFI console path contains exactly one device (either
    serial or VGA), 2.6.6 and newer kernels default to that device
    automatically.  So if you remove "console=" arguments, you can use
    the same elilo configuration to boot any 2.6.6 or newer kernel
    with or without patch [1].

    If you need to boot kernels older than 2.6.6 (including RHEL3 and
    SLES9), keep an 'append="console=ttyS0"' line in those elilo.conf

    Non-HP machines will still need "console=" for serial consoles
    because they don't supply the HCDP table.

[3] The HP management card (MP) causes confusion because it is always
    active as an EFI console, even if it doesn't appear in the EFI
    console path.  If your console path is set to a non-MP UART, and
    you happen to be attached to the MP UART, everything works in EFI,
    but the kernel will think the non-MP UART is the console, so you
    won't see any kernel output.
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Received on Fri Nov 5 15:51:36 2004

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