PCIE CXL

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CXL (Express Compute Link) HW validation

Integrate and validate CXL protocol in a sumulated env. with Synopsys VCS and Virtual Platform (SIMICs).

PCI/PCIe

• Basics: [1], [2], and [3]
• PCIe enumaration, bus-device-function, PCIe controller, bridge, endpoints: [4], and [5]
• From Linux kernel and device tree:
  • What PCIe host driver reads from device tree [6]
  • Accessing PCIe Config Regs on [7]
• Compiled a doc on "Single Root Enumeration Example" [8]

Express Compute Link

• Spec revision 2.0 [9]
• https://bwidawsk.net/blog/2022/6/compute-express-link-intro/

SIMICs

• Run SIMICs tutorial for the Simics Quick-Start Platform (QSP), extended with a custom Mandelbrot accelerator PCI-express (PCIe) add-in card in [10].

  First install SIMICs. SIMICs is provided by Intel in a public release [11] and sold commercially by Wind River. Intel's free-of-charge version supports only Intel Architecture. Follow the User Guide [12] and open Documentation through cd ~/simics-projects/my-simics-project-1/; ./documentation &. The PCIe system the tutorial is about looks as in the fig. below:

• Read through the Documentation (opened in the bullet point above):
  • Model Builder's User Guide
  • Device Modeling Language 1.4 Reference Manual
  • API Reference Manual

Synopsys VCS simulator [13]

An interesting similarity is an Aglilex FPGA-Silicon system from Intel (former Altera) with Coherent Processor Attach with Compute Express Link (CXL) (on the very left hand side in the Fig. below)

It enables creation or use of an FPGA-based accelerator sittin on the R-tile, which is incorporated in selected members of the Intel® Agilex™ I-series and Intel® Agilex™ M-series FPGA families [14]. As an option it also enables VCS simulation for protocol compliance.

References

[1] http://xillybus.com/tutorials/pci-express-tlp-pcie-primer-tutorial-guide-1
[2] PCI_Express_Basics_Background
[3] PCIE bridge in device tree
[4] https://www.khoury.northeastern.edu/~pjd/cs7680/homework/pci-enumeration.html
[5] https://wiki.osdev.org/PCI
[6] https://elinux.org/Device_Tree_Usage#PCI_Host_Bridge
[7] IA Accessing PCI Express Configuration Registers Using Intel Chipsets
[8] Single Root Enumeration Example
[9] CXL spec
[10] w02-builder-workshop-instructions.pdf
[11] https://www.intel.com/content/www/us/en/developer/articles/guide/simics-simulator-installation.html
[12] https://www.intel.com/content/www/us/en/developer/articles/guide/simics-simulator-get-started.html
[13] http://cc.ee.ntu.edu.tw/~ric/teaching/SoC_Verification/S06/Homework/HW1/vcs.pdf
[14] https://www.intel.co.uk/content/www/uk/en/products/details/fpga/intellectual-property/interface-protocols/cxl-ip.html