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Visitor pvanleeuwen
Visitor
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Registered: ‎12-17-2018

How do I get PCIE Gen3 X16 working on a VCU118 Rev 2.0 board

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Hi,

I have a VCU118 Rev 2.0 board that is supposed to be able to do PCIE Gen3 x16 according to the User Guide.
I double checked VCCint using SysMon and this is indeed 0.85V.

However, when I create a design using PCIE Gen3 x16, it does not work reliably. It apparently does link train, as I can see it using lspci, but I cannot actually use it from my application.
If I reconfigure the design for either PCIE Gen2 x16 -or- PCIE Gen3 x8, it works just fine, so I'm pretty confident the problem is with the PCIE configuration.

I did notice this remark in the User Manual: "When creating FPGA designs for the VCU118, the correct VCCINT must be chosen in the Xilinx Vivado tool.", but I have not been able to find any such option in the Vivado tool. Perhaps that is the reason it doesn't work? But then I'd like to know where to find the VCCint selection in the tool ...

 

Regards,
Pascal

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Visitor pvanleeuwen
Visitor
401 Views
Registered: ‎12-17-2018

Re: How do I get PCIE Gen3 X16 working on a VCU118 Rev 2.0 board

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I can hereby confirm that enabling narrow burst support solved the issue :-) i.e this was pilot error, I guess.

But still, to anyone out there designing with the PCIE AXI bridge: I would strongly recommend ENABLING narrow burst support (it shouldn't hurt except maybe for adding a few more LUTs) UNLESS you have a very good reason to disable it and are VERY sure you are not going to need those narrow bursts!

(if you disable it and then later try to upgrade the core settings to something with a wider AXI interface, chances are significant that you forget to enable narrow burst support again ... I just learned the hard way)

 

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Moderator
Moderator
501 Views
Registered: ‎08-10-2007

Re: How do I get PCIE Gen3 X16 working on a VCU118 Rev 2.0 board

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What version of the core are you using?  Please ensure you are using v3.1 or later, using Vivado 2017.1 or later.

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Visitor pvanleeuwen
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491 Views
Registered: ‎12-17-2018

Re: How do I get PCIE Gen3 X16 working on a VCU118 Rev 2.0 board

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I'm using Vivado 2018.2, PCIE DMA/Bridge Subsystem version appears to be 4.1 if I have to believe the block diagram re-customization dialog box ...

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Visitor pvanleeuwen
Visitor
453 Views
Registered: ‎12-17-2018

Re: How do I get PCIE Gen3 X16 working on a VCU118 Rev 2.0 board

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I think I just realised what my problem is here ... still have to try, but very plausible.

The thing is, my AXI master is 256 bit wide doing only 256 bit transfers. Since the PCIE bridge AXI interface for Gen2x16 or Gen3x8 is also 256 bit wide, I had the narrow burst support disabled, since not needed.

BUT ... when I switch to PCIE Gen3x16, the AXI width increases to 512 bits. So I *think* I need to enable narrow burst support now ...

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Visitor pvanleeuwen
Visitor
402 Views
Registered: ‎12-17-2018

Re: How do I get PCIE Gen3 X16 working on a VCU118 Rev 2.0 board

Jump to solution

I can hereby confirm that enabling narrow burst support solved the issue :-) i.e this was pilot error, I guess.

But still, to anyone out there designing with the PCIE AXI bridge: I would strongly recommend ENABLING narrow burst support (it shouldn't hurt except maybe for adding a few more LUTs) UNLESS you have a very good reason to disable it and are VERY sure you are not going to need those narrow bursts!

(if you disable it and then later try to upgrade the core settings to something with a wider AXI interface, chances are significant that you forget to enable narrow burst support again ... I just learned the hard way)