Description of problem:
Installation of RHEL4U4 off a ahci SATA cdrom fails.  The installation process
fails to load the cdrom driver correctly and prompts the user to select the
driver.  However, the relevant driver (ahci) is already loaded.  The problem
seems to happen in the 'install' scenario only. After a successful install
(through NFS), the RHEL kernel 2.6.9-42.EL boots up fine and even recognizes the
cd/dvd drive.  Surprisingly, it is the exact same kernel and set of modules used
for the anaconda install kernel, and, the cdrom does not get recognized during
install!!

Version-Release number of selected component (if applicable):
RHEL4U4


How reproducible:
All the time.  This happened with more than one machine in our labs.

Steps to Reproduce:
1. Start RHEL4 U4 installation from a cdrom attached to the ahci SATA port
2. Proceed to the point where the installation process needs to mount the cdrom.
 Installation process fails to detect the cdrom.

  
Actual results:
Installation failure through CDROM

Expected results:
Successful installation from CDROM

Additional info:
Attaching the dmesg from same machine 1. With the full distro running off the
disk 2. Booting the machine off the cdrom and falling back into rescue mode
(loading the rescue image over NFS).  Please note the timeout error in dmesg
while probing for the cdrom in the latter case:

scsi1 : ahci
ata3: SATA link up 1.5 Gbps (SStatus 113)
ata3: dev 0 cfg 49:0f00 82:0218 83:4000 84:4000 85:0218 86:0000 87:4000 88:101f
ata3: dev 0 ATAPI, max UDMA/66
ata3: qc timeout (cmd 0xef)
ata3: failed to set xfermode (err_mask=0x4)

I don't notice the timeout on booting the installed kernel from the disk:

scsi1 : ahci
ata3: SATA link up 1.5 Gbps (SStatus 113)
ata3: dev 0 cfg 49:0f00 82:0218 83:4000 84:4000 85:0218 86:0000 87:4000 88:101f
ata3: dev 0 ATAPI, max UDMA/66
ata3: dev 0 configured for UDMA/66
scsi2 : ahci