Intel® FSP External Architecture Specification v2.2 Has Been Released

[Desimone, Nathaniel L]

Hi Everyone,



We are pleased to announce that the FSP External Architecture Specification v2.2 has been posted to https://www.intel.com/fsp!



Highlights



  *   Multi-Phase Silicon Initialization – A new optional API has been added to FSP-S to address some of the ongoing community feedback surrounding FSP-S. In general, the feedback has been that FSP-S is too monolithic. FspSiliconInit() does a large amount of initialization in one API call; so much that it has made integration difficult in some cases. For example, firmware update/recovery flows. To address this, a new FspMultiPhaseSiInit() API has been added which splits FSP-S into multiple parts. This allows the bootloader to add board specific code throughout the SiliconInit flow as needed. The breakdown of silicon initialization steps may vary per product and will be detailed in the Integration Guide. FspMultiPhaseSiInit() is only used in API mode. In dispatch mode, equivalent functionality can be achieved using PPIs with less complexity.
  *   FSP Event Handlers – This new feature enables FSP to generate events messages to aid in the debugging of firmware issues. This eliminates the need for FSP to directly write debug messages to the UART. Instead FSP signals the bootloader to inform it of a new debug message. This allows the bootloader to provide board specific methods of reporting debug messages beyond the UART. This brings feature parity between dispatch mode and API mode as FSP 2.1 defined a similar method for dispatch mode.



Roadmap



TigerLakeFspBinPkg provides the first implementation of FSP 2.2. Tiger Lake FSP implements 2 phases for FSP-S: FspSiliconInit() will return after TCSS (“Type-C Sub System” – Integrated USB-C & Thunderbolt 4) initialization is complete. The second phase, invoked by FspMultiPhaseSiInit(), will initialize the graphics framebuffer and lock SAI/SPI writes. This allows board specific USB-C programming to be done before FSP attempts to start early video, and also provides a potentially convenient location for firmware update flows. Looking forward, our upcoming Alder Lake platform will also have FSP 2.2 support.



Does Anything Need to Change in coreboot?



In the strictest sense, no. FSP will only use Multi-Phase Silicon Initialization and FSP Event Handlers if the bootloader explicitly enables them. By default, they are disabled which makes the flow is fully backwards compatible with FSP 2.1. However, in order to leverage these new features coreboot will need to implement support for them. These changes were driven by community feedback and we are optimistic that they are welcome improvements.