AMD Hudson/Yangtze: Enable support for SATA port multipliers

This patch sets a bit in the Yangtze southbridge to enable
the extra protocol necessary to handle port multiplier chips.
This has been turned on during most of Kabini development
without any notable impact. Olive Hill has an optional daughter
board that incorporates Silicon Image Steel Vines chips.  This
change has been tested with and without the daughter board.  This
change can be regression tested using any Hudson-based motherboard,
although it has no impact on boards with discreet Hudson/Bolton
southbridges.

This was tested for impact on SATA performance in the absence of
a port multiplier using the IOZone benchmarks within the Phoronix
Test Suite.  A SATA 3 hard drive (6.0 Gbps) and an SSD were
connected to the ports on Olive Hill without using the port
multiplier card.  The test results contained more run-to-run
variation within the same configuration than was seen in the
aggregate results comparing the interface with and without the
port multiplier protocol additions.  In other words, the test
had less accuracy than the impact caused by turning on port
multiplier support.

Change-Id: Ie87873b093f3e2a6a5c83b96ccb6c898d3e25f72
Signed-off-by: Bruce Griffith <bruce.griffith@se-eng.com>
Reviewed-by: Martin Roth <martin.roth@se-eng.com>
Reviewed-by: Dave Frodin <dave.frodin@se-eng.com>
Reviewed-on: http://review.coreboot.org/3808
Tested-by: build bot (Jenkins)

0 files changed, 0 insertions, 0 deletions