Bug 707008

Modern hardware may be equipped with multiple PCI host bridges. The default MRG Realtime kernel settings are to use one PCI bridge, which means that some devices may be inaccessible to the kernel. 

The following line of output from the kernel boot indicates multiple PCI host bridges present (the output for the current boot may be found in /var/log/dmesg):

pci_root PNP0A03:00: ignoring host bridge windows from ACPI; boot with "pci=use_crs" to use them

If this output is seen when booting MRG Realtime on your system, edit the corresponding boot entry in /etc/grub.conf and add the text:  "pci=use_crs" to the kernel line. This will enable the use of the ACPI property "Current Resource Settings" to enumerate all pci host bridges available.

It also needs to come a release note on ATI Radeon cards as well.  Some of them results in a kernel backtrace during boot.  It might be that the physical VGA based console will not work in this case.  The workaround is to add 'radeon.hw_i2c=0' in the kernel command line.

(In reply to comment #2)
> It also needs to come a release note on ATI Radeon cards as well.  Some of them
> results in a kernel backtrace during boot.  It might be that the physical VGA
> based console will not work in this case.  The workaround is to add
> 'radeon.hw_i2c=0' in the kernel command line.

Agreed, I forgot that we needed to add a note about radeon.hw_i2c=0. Something along the lines of:

If the system display adapter does not function properly and is an ATI Radeon, adding the boot parameter string "radeon.hw_i2c=0" to the grub entry for the kernel may be a workaround for this issue.

    Technical note added. If any revisions are required, please edit the "Technical Notes" field
    accordingly. All revisions will be proofread by the Engineering Content Services team.
    
    New Contents:
Release Note Entry for c#1:

The MRG Realtime Kernel uses one PCI bridge by default, despite the fact that modern hardware is commonly equipped with multiple PCI host bridges. Due to this default setting, some devices may be inaccessible to the kernel.

The below line, if present in the kernel boot output (located at /var/log/dmesg), indicates an inconsistency in the number of PCI host bridges in the hardware and the MRG Realtime kernel:

pci_root PNP0A03:00: ignoring host bridge windows from ACPI; boot with
"pci=use_crs" to use them

Workaround:

If the previously stated kernel boot output displays, edit the corresponding boot entry at /etc/grub.conf and add the text below to the kernel line:

pci=use_crs

This edit enables the use of the ACPI property "Current Resource Settings" to enumerate all available Host Bridges.


Release Note Entry for c#2, c#3:

The system display adapter may not function correctly if an ATI Radeon display adapter is in use.

Workaround:

Add the below boot parameter string to the grub entry for the kernel:

radeon.hw_i2c=0

Looks like we have "one more issue" that needs to be addressed with a Release Note. 

The kernel-rt-doc package conflicts with the kernel-doc package in RHEL6. The work around is to only install one or the other package and not both. This file path conflict will be addressed in subsequent releases of MRG Realtime but for now please use the workaround and only install kernel-rt-doc or kernel-doc, not both.

Moving back to ASSIGNED so that comment#6 can be addressed.

    Technical note updated. If any revisions are required, please edit the "Technical Notes" field
    accordingly. All revisions will be proofread by the Engineering Content Services team.
    
    Diffed Contents:
@@ -24,4 +24,13 @@
 
 Add the below boot parameter string to the grub entry for the kernel:
 
-radeon.hw_i2c=0+radeon.hw_i2c=0
+
+
+Release Note Entry for c#6:
+
+Due to a path conflict, the kernel-rt-doc package conflicts with the kernel-doc package in Red Hat Enterprise Linux 6.
+
+Workaround:
+
+To circumvent this conflict, only one of the two packages can be installed at a time.