[SOLVED] More than 4 serial ports (64-bit RHEL 5.5)

[histrungalot]

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:

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:

# 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:

# 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:

# 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?

$ 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
$

[atreyu]

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

[histrungalot]

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.

[atreyu]

Excellent, glad you got it sorted. I'll go ahead and mark this thread as Solved for you.