Re: [patch 29/30] sata_nv: don't read shadow registers when in ADMA mode

[Jeff Garzik <jeff@garzik.org>]

akpm@linux-foundation.org wrote:
> From: Robert Hancock <hancockr@shaw.ca>
> 
> Reading from the ATA shadow registers while we are in ADMA mode may cause
> undefined behavior.  Don't read the ATA status register when completing
> commands for this reason, it shouldn't be needed as the controller will
> notify us if the command failed.  Also, don't allow commands with result
> taskfile requested to execute in ADMA mode, since that requires accessing
> the shadow registers.  We also still need to override tf_read since libata
> will read the result taskfile on a command failure, and we need to go into
> port register mode before allowing this.
> 
> Signed-off-by: Robert Hancock <hancockr@shaw.ca>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> ---
> 
>  drivers/ata/sata_nv.c |   33 ++++++++++++++++++++-------------
>  1 file changed, 20 insertions(+), 13 deletions(-)

Robert, do you think this should be pushed into #upstream-fixes (2.6.21-rc)?

I lean towards "yes", since it is a needed-by-hardware fix, but I also 
am interested in testing feedback since it is so late in the 2.6.21-rc game.

	Jeff