topic PCIe: Virtual channels in i.MX Processors

PCIe: Virtual channels

julian_dietrich — Fri, 05 Apr 2019 13:30:27 GMT

Hey all,

I need to know which NXP MCUs/MPUs supports more then one Virtual Channel (VC) for PCIe.

I need to realize isochronous data transfers over PCIe.

Thanks in advance!

Re: PCIe: Virtual channels

igorpadykov — Sat, 06 Apr 2019 02:47:39 GMT

Hi Julian

virtual channels are supported, for example this is described in

sect.48.2.4 Configuration-Dependent Module (CDM)

i.MX 6Dual/6Quad Applications Processor Reference Manual

or sect.19.2.1.2 Features

i.MX 8DualXPlus/8QuadXPlus Applications Processor Reference Manual

Best regards
igor
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Re: PCIe: Virtual channels

julian_dietrich — Mon, 08 Apr 2019 08:33:29 GMT

Thanks Igor!

Maybe I'm blind but in both documents I can't find any answer about how many VC's are supported?

Furthermore I'm quite new in the PCIe-technology and I have a general question:

I want to connect several PCIe-endpoints via a PCIe-switch and the communication between the endpoints must be isochronous.

Is it true, that for isochronous data transfers I need more then one VC also in the endpoints?

Or are the several VCs only for the PCIe switch required?

Re: PCIe: Virtual channels

dav1 — Wed, 14 Aug 2019 09:54:44 GMT

julian.dietrich@hbm.com Did you solve this? curious which pcie switch you used?

Re: PCIe: Virtual channels

julian_dietrich — Thu, 15 Aug 2019 08:30:18 GMT

Hi dav1,

It turns out that you need the VC-capability for all connected PCIe-parts in the system. So while the enumeration phase, the RC will scan the capabilities of each part/port, and when the Endpoint has only one VC, the hole communication path between RC/Switch/EP will only use one VC, even if the switch itself has more than one VC.

For me it doesn't make sense - but that's the way it works...

In the end we kicked all VC/TC-schemes for our system. It is very less supported by manufactures, especially for EPs.

We're going the way to only have realtime/isochronous data in our system. Thus, we won't have to seperate these data streams via VC/TC anymore.

Re: PCIe: Virtual channels

dav1 — Thu, 21 Nov 2019 01:29:37 GMT

Thanks for the comments Julian,

what switch IC did you use?