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enjoy-digital / litepcie

Small footprint and configurable PCIe core
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Support for Xilinx soft PCIe PHY? #83

Open Elgox2 opened 2 years ago

Elgox2 commented 2 years ago

Hello,

I'm wondering if parts of this project can be used to control the Xilinx soft PCIe PHY (PG239)? If I'm right, the provided examples only use the hardened-in-silicon IPs from Xilinx.

Any experience with that core, or do you known some other resources for that?

Thanks :)

enjoy-digital commented 2 years ago

Hello @Elgox2,

LitePCIe is indeed using the hardened IPs with TLP interfaces. The Data Link and Transaction Layer will be missing. So this will not be directly supported but it could be a good intermediate step for a full open-source PCIe PHY. The Xilinx PHY could be reused + LitePCIe and the Data Link/Transaction Layers would be developed. Once working, we could also try to replace the PHY, this will probably consist of reusing LiteICLink wrappers + handling LTSSM.

JCBuck commented 2 years ago

Hi @Elgox2 and @enjoy-digital,

Perhaps this question is better suited for Xilinx themselves, but according to (PG239):

The Vivado® IP catalog does not allow generation of this IP for all UltraScale™ and UltraScale+™
devices; however, if a device is selected and has the same transceiver type as the desired device
(UltraScale GTH, UltraScale+ GTH or UltraScale+ GTY), the IP can then be migrated to the
desired part.
Currently, the IP can be generated for the following devices:
• UltraScale+: ZU9EG (GTH), VU3P (GTY), and VU9P(GTY).
• UltraScale: KU040 (GTH), KU115 (GTH), VU440 (GTH), and VU440 ES2 (GTH)

I'm looking at a Kintex-7 KU9P which does not contain any PCIE4 or PCIE4C blocks but does have 16Gb/s GTH transceivers according to ds890

Does the verbiage in PG239 imply that the soft PHY could be modified to work with the KU9P variant and subsequently LicePCIe, if and when the remaining layers are implemented? I'm not too sure if there are any other limitations hardware and timing wise in the FPGA that would otherwise be required for a working soft PCIe implementation.

enjoy-digital commented 2 years ago

Hi @JCBuck,

it seems the IP could indeed be generated for your device, but as I was describing in the previous message, it would still requires the Data Link/Transaction Layer to be implemented to work with LitePCIe.