cbfs: Add LZ4 in-place decompression support for pre-RAM stages

This patch ports the LZ4 decompression code that debuted in libpayload
last year to coreboot for use in CBFS stages (upgrading the base
algorithm to LZ4's dev branch to access the new in-place decompression
checks). This is especially useful for pre-RAM stages in constrained
SRAM-based systems, which previously could not be compressed due to
the size requirements of the LZMA scratchpad and bounce buffer. The
LZ4 algorithm offers a very lean decompressor function and in-place
decompression support to achieve roughly the same boot speed gains
(trading compression ratio for decompression time) with nearly no
memory overhead.

For now we only activate it for the stages that had previously not been
compressed at all on non-XIP (read: non-x86) boards. In the future we
may also consider replacing LZMA completely for certain boards, since
which algorithm wins out on boot speed depends on board-specific
parameters (architecture, processor speed, SPI transfer rate, etc.).

BRANCH=None
BUG=None
TEST=Built and booted Oak, Jerry, Nyan and Falco. Measured boot time on
Oak to be about ~20ms faster (cutting load times for affected stages
almost in half).

Change-Id: Iec256c0e6d585d1b69985461939884a54e3ab900
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/13638
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

1 files changed, 21 insertions, 0 deletions

diff --git a/util/cbfstool/lz4/lib/README.md b/util/cbfstool/lz4/lib/README.md
new file mode 100644
index 0000000000..f6ebf5e10b
--- /dev/null
+++ b/util/cbfstool/lz4/lib/README.md
@@ -0,0 +1,21 @@
+LZ4 - Library Files
+================================
+
+The __lib__ directory contains several files, but you don't necessarily need them all.
+
+To integrate fast LZ4 compression/decompression into your program, you basically just need "**lz4.c**" and "**lz4.h**".
+
+For more compression at the cost of compression speed (while preserving decompression speed), use **lz4hc** on top of regular lz4. `lz4hc` only provides compression functions. It also needs `lz4` to compile properly.
+
+If you want to produce files or data streams compatible with `lz4` command line utility, use **lz4frame**. This library encapsulates lz4-compressed blocks into the [official interoperable frame format]. In order to work properly, lz4frame needs lz4 and lz4hc, and also **xxhash**, which provides error detection algorithm.
+(_Advanced stuff_ : It's possible to hide xxhash symbols into a local namespace. This is what `liblz4` does, to avoid symbol duplication in case a user program would link to several libraries containing xxhash symbols.)
+
+A more complex "lz4frame_static.h" is also provided, although its usage is not recommended. It contains definitions which are not guaranteed to remain stable within future versions. Use for static linking ***only***.
+
+The other files are not source code. There are :
+
+ - LICENSE : contains the BSD license text
+ - Makefile : script to compile or install lz4 library (static or dynamic)
+ - liblz4.pc.in : for pkg-config (make install)
+
+[official interoperable frame format]: ../lz4_Frame_format.md