Help / Clarification regarding M2x

The M.2 socket on the Edge V supports 4 full-duplex lane PCIe 2.1:

The M.2 socket on the Vim3 supports PCIe 2.0 (one lane ), and M.2 2280 NVMe SSD, USB 2.0, I2S, I2C, ADC, 100M Ethernet PHY interface, GPIO

M2X compatibility matrix states:

VIM3 (Full-Featured, PCIe x1 Lane)
Edge-V (SSD-only, PCIe x4 Lane)

Which means when connecting M2X to Edge-V the LTE module on the M2X will not be recognized.

Can anyone please explain where this limitation comes from?
Does that mean the issue is with USB2 support on the SBC side?
Or does the problem reside with the LTE modules themselves?

Thank you.

Hello, I would assume it has to do with the configurations of the respective M.2 sockets themselves. If you compare the specs of the M.2 socket on each…while the Edge dedicates its socket to the 4 lanes, because the 3399 supports that, the socket on the VIM3 uses one lane, freeing up room for other functions. PCI-e single lane likely a limitation of the a311d SoC’s PCI-e controller.
See A311D data sheet, maybe the answer is there.

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Yes, the LTE module with USB interface, and you almost cannot find a LTE module with PCIe interface.

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Thank you both for your answers.
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I have been scouring the detailed specifications of a number of LTE modules.
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It seems Sierra Wireless has redacted its docs and retracted the sections pertaining of PCIe support for recent LTE chips such as em7565 and em7511, see page 4 and 19 of this document:

https://source.sierrawireless.com/resources/airprime/minicard/75xx/airprime_em7565_product_technical_specification/
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Telit states on the LM960 detailed specifications “Currently PCIe interface is not supported but will be enabled soon” on page 40 of this document:

Quectel shows PCIe interface as “optional” on the general specs of EP06. I could not find any reference to it in the detailed technical documentation:

@Gouwa,
In your message you say that LTE module with PCIe interface is almost not found.
Almost is better than nil :slight_smile:
Can you suggest an LTE module that would work? Huawei maybe?

@goenjoy will confirm and response here.

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Thank you.
For the benefit of the community, I would like to share that I have reviewed the detailed spec sheets of two additional modules by Fibocom: L850-GL and L860-GL.
L850-GL defaults to PCIe interface and also supports USB.
L860-GL is purely a PCIe based LTE module.
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Unfortunately these are based on Intel chipsets XMM7360 and XMM7560 respectively and there is NO linux driver available working on the PCIe interface for these modules, despite the fact that they are shipped on numerous high end business laptops (Thinkpads X1, HP Spectre, HP Elite, Dell XPS, etc).

As a coincidence it appears the modem division of Intel was acquired by Apple last month… not sure how this will affect Linux driver support…

I look forward to any suggestion of an LTE module that would work using the PCIe interface on Linux.

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