[XS] Change in coreboot[master]: mb/google/rex: change ramstage compression to LZ4

[Wonkyu Kim (Code Review)]

Attention is currently required from: Jamie Ryu, Kapil Porwal, Raj Astekar, Subrata Banik, Tarun Tuli, Wonkyu Kim.

Hello Arthur Heymans, Jamie Ryu, Kapil Porwal, Raj Astekar, Subrata Banik, Tarun Tuli, build bot (Jenkins),

I'd like you to reexamine a change. Please visit

https://review.coreboot.org/c/coreboot/+/75769?usp=email

to look at the new patch set (#4).

Change subject: mb/google/rex: change ramstage compression to LZ4
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mb/google/rex: change ramstage compression to LZ4

for saving boot time, change ramstage compression from LZMA to LZ4.
Boot time saving is around 35ms(30-37ms) while SPI size impact is 230KB.
For detail, refer below.

Existing: LZMA(55.6 ms)
   8:starting to load ramstage                         894,519 (0)
  15:starting LZMA decompress (ignore for x86)         903,556 (9,036)
  16:finished LZMA decompress (ignore for x86)         949,997 (46,441)
   9:finished loading ramstage                         950,179 (182)

Changed: LZ4(17.8ms)
   8:starting to load ramstage                         900,876 (0)
  17:starting LZ4 decompress (ignore for x86)          917,650 (16,774)
  18:finished LZ4 decompress (ignore for x86)          918,690 (1,040)
   9:finished loading ramstage                         918,849 (158)

Size impact( 73KB * 3 = 219KB)
fallback/ramstage              0x62940    stage          240281 LZ4  (405524 decompressed)
fallback/ramstage              0x62940    stage          165452 LZMA (405524 decompressed)

BUG=b:286930648
TEST= Boot to OS and check boot time

Signed-off-by: Wonkyu Kim 
Change-Id: I6610f405d287bff2eb4eee6f09026e3361405ded
---
M src/mainboard/google/rex/Kconfig
1 file changed, 1 insertion(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/69/75769/4