From 09f2921b5dacaf79b391652cecd606be4dd69f50 Mon Sep 17 00:00:00 2001
From: Julius Werner <jwerner@chromium.org>
Date: Tue, 29 Sep 2015 13:51:35 -0700
Subject: 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>
---
 src/vendorcode/google/chromeos/vboot2/Makefile.inc | 1 +
 1 file changed, 1 insertion(+)

(limited to 'src/vendorcode/google/chromeos')

diff --git a/src/vendorcode/google/chromeos/vboot2/Makefile.inc b/src/vendorcode/google/chromeos/vboot2/Makefile.inc
index 61cf71df5a..2ca8a1adc3 100644
--- a/src/vendorcode/google/chromeos/vboot2/Makefile.inc
+++ b/src/vendorcode/google/chromeos/vboot2/Makefile.inc
@@ -72,6 +72,7 @@ ifeq ($(CONFIG_SEPARATE_VERSTAGE),y)
 cbfs-files-$(CONFIG_SEPARATE_VERSTAGE) += $(CONFIG_CBFS_PREFIX)/verstage
 $(CONFIG_CBFS_PREFIX)/verstage-file := $(objcbfs)/verstage.elf
 $(CONFIG_CBFS_PREFIX)/verstage-type := stage
+$(CONFIG_CBFS_PREFIX)/verstage-compression := $(CBFS_PRERAM_COMPRESS_FLAG)
 # Verstage on x86 expected to be xip.
 ifeq ($(CONFIG_ARCH_VERSTAGE_X86_32)$(CONFIG_ARCH_VERSTAGE_X86_64),y)
 $(CONFIG_CBFS_PREFIX)/verstage-options := -a 64 --xip -S ".car.data"
-- 
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