SRU request for LP#210637

[Colin Ian King]


https://bugs.launchpad.net/ubuntu/+source/linux/+bug/210637


SRU Justification
-----------------

Impact: Regression for sata_nv on Hardy - system reboots or causes XFS
filesystem shutdown due to errors.

Fix description: Patch to check for NV_ADMA_STAT_CMD_COMPLETE to handle
a completed command rather than checking for NV_ADMA_STAT_DONE.

Testcase: Turn off drive caching using hdparm -W 0 /dev/sda and exercise
the XFS filesystem on the drive (a HDS7250SASUN500G).

commit a1fe782414b7122d4c0501d3a0988b7302fa586f
Author: Robert Hancock <hancockr at shaw.ca>
Date:   Tue Jan 29 19:53:19 2008 -0600

    sata_nv: fix for completion handling
    
    This patch is based on an original patch from Kuan Luo of NVIDIA,
    posted under subject "fixed a bug of adma in rhel4u5 with
HDS7250SASUN500G".
    His description follows. I've reworked it a bit to avoid some
unnecessary
    repeated checks but it should be functionally identical.
    
    "The patch is to solve the error message "ata1: CPB flags CMD err,
    flags=0x11" when testing HDS7250SASUN500G in rhel4u5.
    I tested this hd in 2.6.24-rc7 which needed to remove the mask in
    blacklist to run the ncq and the same error also showed up.
    
    I traced the  bug and found that the interrupt finished a command
(for
    example, tag=0) when the driver got that adma status is
    NV_ADMA_STAT_DONE  and  cpb->resp_flags is NV_CPB_RESP_DONE.
    However, For this hd, the drive maybe didn't clear bit 0 at this
moment.
    It meaned the hardware  had not completely finished the command.
    If at the same time  the driver freed the command(tag 0) and sended
    another command (tag 0), the error happened.
    
    The notifier register is 32-bit register containing notifier value.
    Value is bit vector containing one bit per tag number (0-31) in
    corresponding bit positions (bit 0 is for tag 0, etc). When bit is
set
    then ADMA indicates that command with corresponding tag number
completed
    execution.
    
    So i added the check notifier code. Sometimes i saw that the
notifier
    reg set some bits  , but the adma status set
NV_ADMA_STAT_CMD_COMPLETE
    ,not NV_ADMA_STAT_DONE. So i added the NV_ADMA_STAT_CMD_COMPLETE
check
    code."
    
    Signed-off-by: Robert Hancock <hancockr at shaw.ca>
    Signed-off-by: Jeff Garzik <jeff at garzik.org>



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