summaryrefslogtreecommitdiff
path: root/payloads
diff options
context:
space:
mode:
authorDuncan Laurie <dlaurie@chromium.org>2011-12-22 10:59:40 -0800
committerStefan Reinauer <stefan.reinauer@coreboot.org>2012-03-30 17:53:39 +0200
commit7389fa945f48c6da6e5f39d871c0efd9dfba93a1 (patch)
tree6698b2500dc28d8270122eee3abf9e4333edfc5a /payloads
parent67e6c2aaf4d4194dac824014197cc684af9750f5 (diff)
downloadcoreboot-7389fa945f48c6da6e5f39d871c0efd9dfba93a1.tar.xz
MTRR: add alternate allocation method for odd memory maps
With >= 4GB memory installed we get a memory map split in the middle due to remap that has boundaries that are inconveniently aligned for MTRRs due to the various UMA regions. 0000MB-2780MB 2780MB RAM (writeback) 2780MB-2782MB 2MB TSEG (uncached/SMRR) 2782MB-2784MB 2MB GFX GTT (uncached) 2784MB-2816MB 32MB GFX UMA (uncached) 2816MB-4096MB 1280MB EMPTY (N/A) 4096MB-5368MB 1272MB RAM (writeback) 5368MB-5376MB 8MB ME UMA (uncached) The default MTRR allocation method of trying to cover everything with one MTRR and then carve out a single uncached region does not work for the GPU aperture which needs write-combining type, and it also has issues trying to cover the uneven boundaries in the avaiable variable MTRRs. My goal was to make a minimal set of changes and avoid modifying behavior on existing systems with an algorithm that is not always optimal for a typical memory layout. So the flag 'above4gb=2' will change these allocation behaviors: 1) Detect the number of available variable MTRRs rather than limiting to hardcoded value. We need every last MTRR. 2) Don't try to cover all RAM with one MTRR, instead let each RAM region get covered independently. 3) Don't assume uma_memory_base is part of the last region and increase the size of that region. In this case the UMA region is carved out from the lower memory region and it is already declared as part of the ram region. 4) If a memory region can't be covered with MTRRs >= 16MB then instead make a larger region and trim it with uncached MTRRs. Change-Id: I5a60a44ab6d3ae2f46ea6ffa9e3677aaad2485eb Signed-off-by: Duncan Laurie <dlaurie@google.com> Reviewed-on: http://review.coreboot.org/761 Tested-by: build bot (Jenkins) Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
Diffstat (limited to 'payloads')
0 files changed, 0 insertions, 0 deletions