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| -rwxr-xr-x | Documentation/soc/amd/family17h.md | 117 |
1 files changed, 71 insertions, 46 deletions
diff --git a/Documentation/soc/amd/family17h.md b/Documentation/soc/amd/family17h.md index 9608b57325..b917c94526 100755 --- a/Documentation/soc/amd/family17h.md +++ b/Documentation/soc/amd/family17h.md @@ -14,13 +14,12 @@ Family 17h products are x86-based designs. This documentation assumes familiarity with x86, its reset state and its early initialization requirements. -To the extent necessary, the role of the Platform Security Processor -(a.k.a. PSP) in system initialization is addressed here. AMD has -historically required an NDA for access to the PSP -specification<sup>1</sup>. coreboot relies on util/amdfwtool to build -the structures and add various other firmware to the final image<sup>2</sup>. -The Family 17h PSP design guide adds a new BIOS Directory Table, similar to -the PSP Directory Table. +To the extent necessary, the role of the AMD Secure Processor (a.k.a. +Platform Security Processor or PSP) in system initialization is addressed +here. The PSP specification<sup>1</sup> is available only with an NDA. +coreboot relies on util/amdfwtool to build the structures and add various +other firmware to the final image<sup>2</sup>. The Family 17h PSP design +guide adds a new BIOS Directory Table, similar to the PSP Directory Table. Support in coreboot for modern AMD products is based on AMD’s reference code: AMD Generic Encapsulated Software Architecture @@ -51,8 +50,13 @@ related firmware images * Embedded Firmware Structure - Signature and pointers used by the PSP to locate the PSP Directory Table and BIOS Directory Table; these items are generated during coreboot build and are located in the SPI ROM -* Verstage - The code to verify the firmware contained in the -writable section of the SPI ROM +* vboot - The generic technology name for verifying/choosing a RW A/B +or fallback RO path. +* verstage - The code (vboot) to verify the firmware contained in the +writable section of the SPI ROM, traditionally run on the x86 processor, +and in some cases a separate stage added to coreboot +* vboot app - A portion of vboot technology designed and compiled +to run on the PSP * APCB - AMD PSP Customization Block - A binary containing PSP and system configuration preferences (analogous to v5 BUILDOPT_ options), and generated by APCBTool to be added to coreboot/utils later @@ -90,7 +94,8 @@ dependency expressions, much functionality is rewritten as libraries, etc. It would, in no way, fit into the v5 model used in coreboot. * For the foreseeable future, AGESA source will distributed only -under NDA. +under NDA. Furthermore, because AGESA's integrated debug services divulge +NDA information, no debug builds will be released to the general public. ## Basic Pre-x86 Boot Flow @@ -102,15 +107,15 @@ The following steps occur prior to x86 processor operation. the SPI ROM * PSP verifies and executes the PSP off-chip bootloader * ChromeOS systems: - * Off-chip bootloader attempts to locate verstage via the RO BIOS + * Off-chip bootloader attempts to locate vboot app via the RO BIOS Directory Table - * If verstage is not found, booting continues with ABLs below - * Verstage initializes, setting up GPIOs, UART if needed, + * If vboot app is not found, booting continues with ABLs below + * vboot app initializes, setting up GPIOs, UART if needed, communication path to the EC, and the SPI controller for direct access to the flash device. - * Verstage verifies the RW sections (as is typically performed by + * vboot app verifies the RW sections (as is typically performed by the main processor) - * Verstage locates the Embedded Firmware Directory within the + * vboot app locates the Embedded Firmware Directory within the verified FMAP section and passes a pointer to the PSP bootloader. If the verification fails, it passes a pointer to the RO header to the bootloader. @@ -166,44 +171,61 @@ jump to protected mode must jump to the physical address in DRAM. Any code that is position-dependent must be linked to run at the final destination. -## Initial coreboot Implementation +## Implementation for coreboot -Supporting Picasso doesn’t fit well with many of the coreboot -assumptions. Initial porting shall attempt to fit within existing -coreboot paradigms and make minimal changes to common code. +Supporting Picasso doesn’t fit perfectly with many of the coreboot +assumptions about x86 processors. Changes are introduced primarily +into arch/x86 to accommodate a processor starting in DRAM and at a +nontraditional reset vector. -### CAR and bootblock +### CAR and early stages -The coreboot bootblock contains features Picasso doesn’t require or -can’t use, and is assumed to execute in an unusable location. -Picasso’s requirement for bootblock in coreboot will be eliminated. +The traditional coreboot bootblock and romstage rely on cache-as-RAM +and a linker script that positions temporary storage accordingly. A +substitute for the DCACHE variables, called EARLYRAM, is introduced. +Like DCACHE, this allows for a consistent mapping of early regions +required across multiple stages prior to cbmem coming online. +Examples are the _preram_cbmem_console and _timestamp. -### Hybrid romstage +Due to Picasso's unique nature of starting with DRAM already available, +no early stages run as execute-in-place (XIP). All post-bootblock +stages are copied from the BIOS flash into DRAM for faster +performance, and these regions are marked reserved later in POST. -Picasso’s x86 reset state doesn’t meet the coreboot expectations -for jumping directly to ramstage. The primary feature of romstage is -also not needed, however there are other important features that are -typically in romstage that Picasso does need. +Unlike CAR-based systems, and because Picasso does not run early +stages as XIP, its early stages are not constrained in their use +of .bss or .data sections. All stages' .bss is zeroed, and all +.data sections are fully R/W at load time. -The romstage architecture is designed around the presence of CAR. -Several features implement ROMSTAGE_CBMEM_INIT_HOOK, expecting to move -data from CAR to cbmem. The hybrid romstage consumes DRAM for the -purpose of implementing the expected CAR storage. This region as well -as the DRAM where romstage is decompressed must be reserved and -unavailable to the OS. +### bootblock -The initial Picasso port implements a hybrid romstage that contains the -first instruction fetched at the reset vector. It minimally configures -flat protected mode, initializes cbmem, then loads the next stage. -Future work will consider breaking the dependencies mentioned above -and/or potentially loading ramstage directly from the PSP. +Picasso uses a bootblock that mirrors a traditional bootblock as much +as possible. Because the image is loaded by the PSP, the bootblock is +not restricted to the top of the BIOS flash device. The compressed +image is added into the PSP's `amdfw.rom` build. + +### vboot app and verstage + +Development is currently underway for the vboot app, and potentially +an x86-based verstage companion. This document shall be updated once +the design is finalized and functioning. Support for the PSP honoring +the presence of the vboot app is available only in certain SKUs. + +### romstage and postcar + +A traditional romstage is maintained for Picasso. The primary reason for +this choice is to remain compatible with coreboot conventions and +to support the FSP 2.0 driver. Picasso's romstage uses an +fsp_memory_init() call to glean the memory map from AGESA. (See below.) +fsp_memory_init() brings cbmem online before returning to the caller. + +No postcar stage is required or supported. ## AGESA v9 on Picasso -Due to the current inability to publish AGESA source, a pre-built -binary solution remains a requirement. The rewrite from v5 to v9 for -direct inclusion into UEFI source makes modifying it for conforming to -the existing v5 interface impractical. +Due to the current restriction on publishing AGESA source, a pre-built +binary solution remains a requirement. Modifying v9 to conform to the +existing v5 binaryPI interface was considered impractical. Given the UEFI nature of modern AGESA, and the existing open source work from Intel, Picasso shall support AGESA via an FSP-like prebuilt @@ -211,12 +233,15 @@ image. The Intel Firmware Support Package<sup>5</sup> combines reference code with EDK II source to create a modular image with discoverable entry points. coreboot source already contains knowledge of FSP, how to parse it, integrate it, and how to communicate with it. +Picasso's FSP is compatible with rev. 2.0 of the External Architecture +Specification. Deviations, e.g., no FSP-T support, shall be published +in an Integration Guide. ## Footnotes -1. “AMD Platform Security Processor BIOS Architecture Design Guide -for AMD Family 17h Processors” (PID #55758) and “AMD Platform -Security Processor BIOS Architecture Design Guide” (PID #54267) for +1. *AMD Platform Security Processor BIOS Architecture Design Guide +for AMD Family 17h Processors* (PID #55758) and *AMD Platform +Security Processor BIOS Architecture Design Guide* (PID #54267) for earlier products 2. [PSP Integration](psp_integration.md) 3. [https://www.amd.com/system/files/TechDocs/44065_Arch2008.pdf](https://www.amd.com/system/files/TechDocs/44065_Arch2008.pdf) |