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I have a 64-bit RHEL 5.5 system and am trying to increase the number of run time uarts to 16. I have tried changing the grub to: Code: title Red ...
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  1. #1
    Just Joined!
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    More than 4 serial ports (64-bit RHEL 5.5)


    I have a 64-bit RHEL 5.5 system and am trying to increase the number of run time uarts to 16. I have tried changing the grub to:
    Code:
    title Red Hat Enterprise Linux Server (2.6.18-194.el5xen)
            root (hd0,0)
            kernel /xen.gz-2.6.18-194.el5 crashkernel=128M@32M
            module /vmlinuz-2.6.18-194.el5xen 8250.nr_uarts=16 ro root=/dev/VolGroup00/LogVol00 rhgb quiet  ramdisk_size=2000000
            module /initrd-2.6.18-194.el5xen.img
    but I get this:
    Code:
    # dmesg | grep -i uart
    Bootdata ok (command line is 8250.nr_uarts=16 ro root=/dev/VolGroup00/LogVol00 rhgb quiet ramdisk_size=2000000)
    Kernel command line: 8250.nr_uarts=16 ro root=/dev/VolGroup00/LogVol00 rhgb quiet ramdisk_size=2000000
    Unknown boot option `8250.nr_uarts=16': ignoring
    This all worked with the 32-bit RHEL 5.5.
    [EDIT] I see that in the 32-bit RHEL 5.5 the /boot/config-2.6.18-194.el5PAE file:
    Code:
    # Serial drivers  32-bit RHEL 5.5
    #
    CONFIG_SERIAL_8250=y
    CONFIG_SERIAL_8250_CONSOLE=y
    CONFIG_SERIAL_8250_PCI=y
    CONFIG_SERIAL_8250_PNP=y
    CONFIG_SERIAL_8250_CS=m
    CONFIG_SERIAL_8250_NR_UARTS=32
    CONFIG_SERIAL_8250_RUNTIME_UARTS=4
    CONFIG_SERIAL_8250_EXTENDED=y
    CONFIG_SERIAL_8250_MANY_PORTS=y
    CONFIG_SERIAL_8250_SHARE_IRQ=y
    CONFIG_SERIAL_8250_DETECT_IRQ=y
    CONFIG_SERIAL_8250_RSA=y
    but in 64-bit RHEL 5.5 I have:
    Code:
    # Serial drivers 64-bit RHEL 5.5
    #
    CONFIG_SERIAL_8250=m
    CONFIG_SERIAL_8250_PCI=m
    CONFIG_SERIAL_8250_PNP=m
    CONFIG_SERIAL_8250_CS=m
    CONFIG_SERIAL_8250_NR_UARTS=32
    CONFIG_SERIAL_8250_RUNTIME_UARTS=4
    CONFIG_SERIAL_8250_EXTENDED=y
    CONFIG_SERIAL_8250_MANY_PORTS=y
    CONFIG_SERIAL_8250_SHARE_IRQ=y
    CONFIG_SERIAL_8250_DETECT_IRQ=y
    CONFIG_SERIAL_8250_RSA=y
    Given it was not a module in the 32-bit version, How do I fix it for the 64-bit version? What am I missing?

    Code:
    $ uname -a 
    Linux dev.com 2.6.18-194.el5xen #1 SMP Tue Mar 16 22:01:26 EDT 2010 x86_64 x86_64 x86_64 GNU/Linux
    $
    Last edited by histrungalot; 11-05-2012 at 03:56 PM.

  2. #2
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    Hi,

    According to this bug report, you are on the right track. Because it is built as a kernel module, those kernel parameters are being ignored. You need to either rebuild the kernel and make that module built-in instead, or pass the 8250 parameters to modprobe. You can add them to a file read by the kernel modprobe system. See this article on that:

    https://access.redhat.com/knowledge/...e_Loading.html

  3. #3
    Just Joined!
    Join Date
    Aug 2011
    Posts
    51

    Lightbulb

    Thanks for you response! I tried and tried to load the module but no luck. Hours later I found out that the kernel version that was loaded was the wrong one (2.6.18-194.el5xen). It should have been just 2.6.18-194.el5 without the xen (What is xen?). After that was installed, I was able to use the 8250.nr_uarts=16 in the grub file because 8250 serial was built into this kernel by default.

    Thanks again.

  4. #4
    Trusted Penguin
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    May 2011
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    Excellent, glad you got it sorted. I'll go ahead and mark this thread as Solved for you.

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