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, 8 insertions, 0 deletions

diff --git a/src/include/cbfs.h b/src/include/cbfs.h
index 0d95387940..2d1921898a 100644
--- a/src/include/cbfs.h
+++ b/src/include/cbfs.h
@@ -35,6 +35,14 @@ int cbfs_boot_locate(struct cbfsf *fh, const char *name, uint32_t *type);
  * the mapping and sets the size of the file. */
 void *cbfs_boot_map_with_leak(const char *name, uint32_t type, size_t *size);
 
+/* Load |in_size| bytes from |rdev| at |offset| to the |buffer_size| bytes
+ * large |buffer|, decompressing it according to |compression| in the process.
+ * Returns the decompressed file size, or 0 on error.
+ * LZMA files will be mapped for decompression. LZ4 files will be decompressed
+ * in-place with the buffer size requirements outlined in compression.h. */
+size_t cbfs_load_and_decompress(const struct region_device *rdev, size_t offset,
+	size_t in_size, void *buffer, size_t buffer_size, uint32_t compression);
+
 /* Load stage into memory filling in prog. Return 0 on success. < 0 on error. */
 int cbfs_prog_stage_load(struct prog *prog);