coreboot 4.22 & 4.22.01 releases

The next release is planned for the 19th of February, 2024

These notes cover the latest updates and improvements to coreboot over the past three months. A big thank you to the returning contributors as well as the 14 individuals who committed code for the first time. We greatly appreciate everyone’s dedication and expertise. As with past releases, this one reflects a commitment to open source innovation, security enhancements, and expanding hardware support.

4.22.01 release

The week between tagging a release and announcing it publicly is used to test the tagged version and make sure everything is working as we expect. This is done instead of freezing the tree and doing release candidates before the release.

For the 4.22 release cycle we found an uninitialized variable error on the sandybridge/ivybridge platforms and rolled that into the 4.22.01 release package.

coreboot version naming update

This release is the last release to use the incrementing 4.xx release name scheme. For future releases, coreboot is switching to a Year.Month.Sub-version naming scheme. As such, the next release, scheduled for February of 2024 will be numbered 24.02, with the sub-version of 00 implied. If we need to do a fix or future release of the 24.02 release, we’ll append the values .01, .02 and so on to the initial release value.

coreboot default branch update

Immediately after the 4.21 release, the coreboot project changed the default git branch from ‘master’ to ‘main’. For the first couple of months after the change, The master branch was synced with the main branch several times a day, allowing people time to update any scripts. As of 2023-11-01, the sync rate has slowed to once a week. This will continue until the next release, at which time the master branch will be removed.

Significant or interesting changes

x86: support .data section for pre-memory stages

x86 pre-memory stages did not support the .data section and as a result developers were required to include runtime initialization code instead of relying on C global variable definitions.

Other platforms do not have that limitation. Hence, resolving it helps to align code and reduce compilation-based restrictions (cf. the use of ENV_HAS_DATA_SECTION compilation flag in various places of coreboot code).

There were three types of binary to consider:

  1. eXecute-In-Place pre-memory stages
  2. bootblock stage is a bit different as it uses Cache-As-Ram but the memory mapping and its entry code different
  3. pre-memory stages loaded in and executed from Cache-As-RAM (cf. CONFIG_NO_XIP_EARLY_STAGES).

eXecute-In-Place pre-memory stages (#1) rely on a new ELF segment as the code segment Virtual Memory Address and Load Memory Address are identical but the data needs to be linked in cache-As-RAM (VMA) to be stored right after the code (LMA).

bootblock (#2) also uses this new segment to store the data right after the code and it loads it to Cache-As-RAM at runtime. However, the code involved is different.

Not eXecute-In-Place pre-memory stages (#3) did not need any special work other than enabling a .data section as the code and data VMA / LMA translation vector is the same.

Related important commits:

  • c9cae530e5 (“cbfstool: Make add-stage support multiple ignore sections”)
  • 79f2e1fc8b (“cbfstool: Make add-stage support multiple loadable segments”)
  • b7832de026 (“x86: Add .data section support for pre-memory stages”)

x86: Support CBFS cache for pre-memory stages and ramstage

The CBFS cache scratchpad offers a generic way to decompress CBFS files through the cbfs_map() function without having to reserve a per-file specific memory region.

CBFS cache x86 support has been added to pre-memory stages and ramstage.

  1. pre-memory stages: The new PRERAM_CBFS_CACHE_SIZE Kconfig can be used to set the pre-memory stages CBFS cache size. A cache size of zero disables the CBFS cache feature for all pre-memory stages. The default value is 16 KiB which seems a reasonable minimal value enough to satisfy basic needs such as the decompression of a small configuration file. This setting can be adjusted depending on the platform’s needs and capabilities.

    Note that we have set this size to zero for all the platforms without enough space in Cache-As-RAM to accommodate the default size.

  2. ramstage: The new RAMSTAGE_CBFS_CACHE_SIZE Kconfig can be used to set the ramstage CBFS cache size. A cache size of zero disables the CBFS cache feature for ramstage. Similarly to pre-memory stages support, the default size is 16 KiB.

    As we want to support the S3 suspend/resume use case, the CBFS cache memory cannot be released to the operating system and therefore cannot be an unreserved memory region. The ramstage CBFS cache scratchpad is defined as a simple C static buffer as it allows us to keep the simple and robust design of the static initialization of the cbfs_cache global variable (cf. src/lib/cbfs.c).

    However, since some AMD SoCs (cf. SOC_AMD_COMMON_BLOCK_NONCAR Kconfig) already define a _cbfs_cache region we also introduced a POSTRAM_CBFS_CACHE_IN_BSS Kconfig to gate the use of a static buffer as the CBFS cache scratchpad.

Allow romstage to be combined into the bootblock

Having a separate romstage is only desirable:

  • with advanced setups like vboot or normal/fallback
  • boot medium is slow at startup (some ARM SOCs)
  • bootblock is limited in size (Intel APL 32K)

When this is not the case there is no need for the extra complexity that romstage brings. Including the romstage sources inside the bootblock substantially reduces the total code footprint. Often the resulting code is 10-20k smaller.

This is controlled via a Kconfig option.

soc/intel/cmn/gfx: Add API to report presence of external display

This implements an API to report the presence of an external display on Intel silicon. The API uses information from the transcoder and framebuffer to determine if an external display is connected.

For example, if the transcoder is attached to any DDI ports other than DDI-A (eDP), and the framebuffer is initialized, then it is likely that an external display is present.

This information can be used by payloads to determine whether or not to power on the display, even if eDP is not initialized.

device/pci_rom: Set VBIOS checksum when filling VFCT table

AMD’s Windows display drivers validate the checksum of the VBIOS data in the VFCT table (which gets modified by the FSP GOP driver), so ensure it is set correctly after copying the VBIOS into the table if the FSP GOP driver was run. Without the correct checksum, the Windows GPU drivers will fail to load with a code 43 error in Device Manager.

Additional coreboot changes

  • Move all ‘select’ statements from files to Kconfig
  • acpigen now generates variable-length PkgLength fields instead of a fixed 3-byte size to improve compatibility and to bring it in line with IASL
  • Work to allow Windows to run on more Chromebooks
  • General cleanup and reformatting
  • Add initial AMD openSIL implementation
  • Add ACPI table generation for ARM64
  • Stop resetting CMOS during s3 resume even if marked as invalid
  • Comply with ACPI specification by making _STR Unicode strings
  • Fix SMM get_save_state calculation, which was broken when STM was enabled
  • SNB+MRC boards: Migrate MRC settings to devicetree
  • Work on chipset devicetrees for all platforms

Changes to external resources

Toolchain updates

  • Upgrade GMP from 6.2.1 to 6.3.0
  • Upgrade binutils from 2.40 to 2.41
  • Upgrade MPFR from 4.2.0 to 4.2.1

Git submodule pointers

  • amd_blobs: Update from commit id 6a1e1457af to e4519efca7 (16 commits)
  • arm-trusted-firmware: Update from commit id 37366af8d4 to 88b2d81345 (214 commits)
  • fsp: Update from commit id 3beceb01f9 to 481ea7cf0b (15 commits)
  • intel-microcode: Update from commit id 6f36ebde45 to 6788bb07eb (1 commit)
  • vboot: Update from commit id 0c11187c75 to 24cb127a5e (24 commits)
  • genoa_poc/opensil: New submodule updated to 0411c75e17 (41 commits)

External payloads

  • U-Boot: Use github mirror and the latest version
  • edk2: Update default branch for MrChromebox repo to 2023-09

Platform Updates

Added 17 mainboards

  • AMD Onyx
  • Google: Anraggar
  • Google: Brox
  • Google: Chinchou
  • Google: Ciri
  • Google: Deku
  • Google: Deku4ES
  • Google: Dexi
  • Google: Dochi
  • Google: Nokris
  • Google: Quandiso
  • Google: Rex4ES EC ISH
  • Intel: Meteorlake-P RVP with Chrome EC for non-Prod Silicon
  • Purism Librem 11
  • Purism Librem L1UM v2
  • Siemens FA EHL
  • Supermicro X11SSW-F

Added 1 SoC

  • src/soc/amd/genoa

Statistics from the 4.21 to the 4.22 release

  • Total Commits: 977
  • Average Commits per day: 10.98
  • Total lines added: 62993
  • Average lines added per commit: 64.48
  • Number of patches adding more than 100 lines: 60
  • Average lines added per small commit: 37.55
  • Total lines removed: 30042
  • Average lines removed per commit: 30.75
  • Total difference between added and removed: 32951
  • Total authors: 135
  • New authors: 14

Significant Known and Open Issues

Issues from the coreboot bugtracker:

Payload-specific issues

# Subject
499 edk2 boot fails with RESOURCE_ALLOCATION_TOP_DOWN enabled
496 Missing malloc check in libpayload
484 No USB keyboard support with secondary payloads
414 X9SAE-V: No USB keyboard init on SeaBIOS using Radeon RX 6800XT

Platform-specific issues

# Subject
509 SD Card hotplug not working on Apollo Lake
507 Windows GPU driver fails on Google guybrush & skyrim boards
506 APL/GML don’t boot OS when CPU microcode included “from tree”
505 Harcuvar CRB - 15 of 16 cores present in the operating system
499 T440p - EDK2 fails with RESOURCE_ALLOCATION_TOP_DOWN enabled
495 Stoney Chromebooks not booting PSPSecureOS
478 X200 booting Linux takes a long time with TSC
474 X200s crashes after graphic init with 8GB RAM
457 Haswell (t440p): CAR mem region conflicts with CBFS_SIZE > 8mb
453 Intel HDMI / DP Audio not present in Windows after libgfxinit
449 ThinkPad T440p fail to start, continuous beeping & LED blinking
448 Thinkpad T440P ACPI Battery Value Issues
446 Optiplex 9010 No Post
439 Lenovo X201 Turbo Boost not working (stuck on 2,4GHz)
427 x200: Two battery charging issues
412 x230 reboots on suspend
393 T500 restarts rather than waking up from suspend
350 I225 PCIe device not detected on Harcuvar

Plans for the next release

  • Finish adding chipset device trees for all SOCs
  • Improve code for options/setup
  • Start reformatting C files with clang-format
  • Add warning/error step for Makefiles at the end