[S] Change in coreboot[master]: mb/google/skyrim: Switch from LZMA to LZ4 compression for ramstage

[Martin L Roth (Code Review)]

Martin L Roth has submitted this change. ( https://review.coreboot.org/c/coreboot/+/71675 )

Change subject: mb/google/skyrim: Switch from LZMA to LZ4 compression for ramstage
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mb/google/skyrim: Switch from LZMA to LZ4 compression for ramstage

Because skyrim is loading ramstage from SPI with the DMA engine, the
size of the compressed image is less important to load speed than
decompression time.

Because the LZ4 decompression is so much faster than LZMA, compressing
with LZ4 saves us roughly 30ms in boot time.

For size, we're spending roughly 57KiB:
fallback/ramstage 0x9b00 stage 130864 LZMA (305316 decompressed)
fallback/ramstage 0x9b00 stage 189126 LZ4  (305316 decompressed)

Right now we have 2MiB empty space in Skyrim's RO before this change,
and roughly 550KiB empty space in RW, so there aren't currently any
size worries.

Just for fun, I also tested uncompressed ramstage, and it was still
18ms faster than LZMA, but that makes it roughly 12ms slower than LZ4.

BUG=b:264409477
TEST=Boot skyrim, look at boot speed.

Signed-off-by: Martin Roth 
Change-Id: Iedde6fc2db9d702c0ff2b0081e7baa254ac6699f
Reviewed-on: https://review.coreboot.org/c/coreboot/+/71675
Tested-by: build bot (Jenkins) 
Reviewed-by: Fred Reitberger 
Reviewed-by: Arthur Heymans 
Reviewed-by: Paul Menzel 
---
M src/mainboard/google/skyrim/Kconfig
1 file changed, 37 insertions(+), 0 deletions(-)

Approvals:
  build bot (Jenkins): Verified
  Paul Menzel: Looks good to me, but someone else must approve
  Arthur Heymans: Looks good to me, approved
  Fred Reitberger: Looks good to me, approved

diff --git a/src/mainboard/google/skyrim/Kconfig b/src/mainboard/google/skyrim/Kconfig
index 493ecb5..94659db 100644
--- a/src/mainboard/google/skyrim/Kconfig
+++ b/src/mainboard/google/skyrim/Kconfig
@@ -37,6 +37,7 @@
    select I2C_TPM
    select MAINBOARD_HAS_CHROMEOS
    select MAINBOARD_HAS_TPM2
+	select MB_COMPRESS_RAMSTAGE_LZ4
    select SOC_AMD_MENDOCINO
    select SOC_AMD_COMMON_BLOCK_I2C3_TPM_SHARED_WITH_PSP
    select SOC_AMD_COMMON_BLOCK_USE_ESPI