Hi all, This is an info mail for addressing this patch (soc/intel/elkhartlake: Introduce Intel PSE [1]): With the Elkhart Lake Platform Intel has introduced an additional subsystem controller inside the Chipset which can be used to offload different kind of tasks from the main CPU. This controller is called the Programmable Service Engine (PSE) and is an ARM Cortex M7 based CPU with 384 KB of Tightly Coupled Memory (TCM for data and code) and 1MB of L2 SRAM. The firmware this controller executes has to be loaded during boot-time of the main CPU and can be any custom designed piece of firmware that serves the needs of the application. In addition, the PSE can be a Zephyr OS based.
In order to perform the task in a given application, which might be e.g., real-time communication over Time Sensitive Network (TSN), Intel(r) EC Lite Service, Out Of Band (OOB) Management or even a network proxy, there are several SoC internal peripherals that can be assigned to the PSE (.../pci_devs.h [2]). This assignment must be done at boot time of the main CPU and cannot be changed later. So once a peripheral is assigned to the PSE, it disappears from the host subsystem and is only useable with the PSE to perform the task in question. There is one communication channel between the host subsystem and the PSE subsystem so that the host CPU can communicate with the application running on the PSE. IPC HW with HECI protocol. There is further no way that the PSE application can access host dedicated peripherals. To achieve this the PSE is equipped with a dedicated MMU which isolates both subsystems.
As mentioned earlier the Firmware of the PSE needs to be loaded at boot time of the host CPU, this is mandatory for Elkhart Lake. There is a patch on Gerrit provides an interface to load the PSE firmware (soc/intel/elkhartlake: Introduce Intel PSE [1]. This patch does not introduce the PSE-Firmware itself nor does it add a new blob to the coreboot repository. In fact, this patch acquires the PSE firmware to load located inside the CBFS and loads it into DRAM, adds some settings related to the PSE like peripheral ownership and passes this DRAM buffer to the FSP, which then performs the loading of the firmware among with the settings into the PSE controller itself.
Please and thank you, Sheng
[1]: https://review.coreboot.org/c/coreboot/+/55367 [2]: https://review.coreboot.org/c/coreboot/+/58466