Sierra EM9291 on Verdin iMX8MM/P

Technical Support
, ,
1

Hi,

As suggested by the Toradex support team we bought Sierra EM9291 and use it with Verdin iMX8M on a Mallow board.

The modem is not detected, and dmesg suggests that device enumeration fails (phy link never came up).
Furthermore, on device boot, we observe write timeouts on i2c-3 <i2c_imx_write> write timedout.

Could you please help to clarify whether the modem is supported officially (despite not listed in the compatible peripherals list), or do we need to customize dtb?

I can confirm that the device is indeed operating in PCIE mode (PCIE_DIS=0), in the meantime checking further signals.

Thanks for your help in advance.

[   10.134324] imx6q-pcie 33800000.pcie: host bridge /soc@0/pcie@33800000 ranges:
[   10.134374] imx6q-pcie 33800000.pcie:       IO 0x001ff80000..0x001ff8ffff -> 0x0000000000
[   10.134392] imx6q-pcie 33800000.pcie:      MEM 0x0018000000..0x001fefffff -> 0x0018000000
[   10.198409] i2c i2c-3: <i2c_imx_write> write timedout
[   10.205140] lm75: probe of 3-004f failed with error -110
[   10.368620] imx6q-pcie 33800000.pcie: iATU: unroll T, 4 ob, 4 ib, align 64K, limit 4G
[   10.814216] CAN device driver interface
[   11.360598] imx6q-pcie 33800000.pcie: Phy link never came up
[   12.070276] Bluetooth: FW download over, size 623352 bytes
[   12.309331] btmrvl_sdio mmc2:0001:2: sdio device tree data not available
[   12.348725] imx6q-pcie 33800000.pcie: Phy link never came up
[   12.349565] imx6q-pcie 33800000.pcie: PCI host bridge to bus 0000:00
[   12.349583] pci_bus 0000:00: root bus resource [bus 00-ff]
[   12.349592] pci_bus 0000:00: root bus resource [io  0x0000-0xffff]
[   12.349599] pci_bus 0000:00: root bus resource [mem 0x18000000-0x1fefffff]

Software summary
------------------------------------------------------------
Bootloader:               U-Boot
Kernel version:           6.6.84-7.2.0-g87bfb710b6f1 #1-Torizon SMP PREEMPT Mon Mar 31 08:47:48 UTC 2025
Kernel command line:      root=LABEL=otaroot rootfstype=ext4 quiet logo.nologo vt.global_cursor_default=0 plymouth.ignore-serial-consoles splash fbcon=map:3 ostree=/ostree/boot.1/torizon/bc82c85a12c54eb00
Distro name:              NAME="Torizon OS"
Distro version:           VERSION_ID=7.2.0-build.13
Distro variant:           VARIANT="Docker"
Hostname:                 verdin-imx8mm-15557745
------------------------------------------------------------

Hardware info
------------------------------------------------------------
HW model:                 Toradex Verdin iMX8M Mini WB on Verdin Development Board
Toradex version:          0060 V1.1C
Serial number:            15557745
Processor arch:           aarch64
------------------------------------------------------------
2

Hi, I’m the Toradex AI Assistant.

I might make mistakes. Our support team will step in if needed. If I answered your question, please tick the “Solution” checkbox. For follow-up questions to me, please use @ToradexAI in your post.

Did you like my answer? :+1: :-1:

Hello! Thank you for reaching out with detailed information about your setup and issue.

Based on current documentation, the Sierra EM9291 modem is not officially listed as a compatible peripheral for the Mallow carrier board in combination with the Verdin iMX8M Plus (or Mini) SoM. The compatibility list for the Mallow carrier board includes displays, heatsinks, and modules, but does not mention the EM9291 modem (Reference). Official support for this specific modem and carrier board combination is not currently available.

PCIe Device Not Detected (phy link never came up)

The message phy link never came up in your kernel log typically indicates an issue at the PCIe physical link layer—common causes include:

  • Incompatible voltage levels on PCIe, REFCLK, or control signals.
  • Missing or incorrect device tree configuration (for supported devices).
  • Hardware incompatibility between the modem, carrier board, and module.
  • Power-up sequencing issues or PCIe reset not being properly released.

Since the EM9291 is not officially supported, a device tree customization may be required to properly enable the PCIe interface for this device. However, even with correct DT configuration, hardware compatibility needs to be verified, particularly regarding voltage levels and presence of necessary signals (e.g., PERST, CLKREQ, etc.).

I2C Timeout (i2c_imx_write write timedout)

I2C issues likely relate to voltage level mismatches or incorrect pinmuxing. The Mallow board uses 1.8V for I2C signal levels (Reference). Please ensure that all connected I2C devices—including the modem (if it uses I2C for control)—are compatible with 1.8V logic levels. Otherwise, I2C communication may fail, leading to timeouts as seen in your log.

General Troubleshooting Steps

  1. Verify Connections & Signal Levels

    • Ensure the modem is properly seated and all required signals (PCIe power, reset, REFCLK, PERST) are present.
    • Double-check that all involved peripherals support 1.8V logic on I2C and PCIe.

  2. Device Tree Adjustment

    • Look into adjusting the device tree to enable the proper PCIe root complex. Example overlays are available for supported PCIe devices. While not explicitly for EM9291, you may reference them for base configuration.
    • Check for device tree settings related to the Mallow board and PCIe usage on the Verdin iMX8M platform:
      Mallow Carrier Board - Hardware Documentation

  3. Review Software and Kernel Logs

    • Double-check that kernel drivers required by the Sierra modem are available/enabled.
    • Review the full dmesg output for any other PCIe or power domain hints.

  4. Minimal Setup

    • If possible, try removing other peripherals from the carrier board to rule out conflicts or voltage issues.

Additional Resources

Summary

  • The Sierra EM9291 modem is not officially supported with the Mallow carrier and Verdin iMX8M.
  • PCIe enumeration failures (phy link never came up) likely stem from hardware incompatibility or require custom device tree overlays.
  • The I2C voltage level (1.8V on Mallow) should be verified across all connected devices to avoid timeouts.

If you need a general outline for customizing the device tree for PCIe devices or further troubleshooting steps, let me know and I can provide guidance.

Best regards,
Toradex AI Assistant.

3

Dear @simon.isg,

Thank you for your post and the provided information. We have been in contact with Semtech/Sierra regarding the hurdle you are currently facing. Here is the information we got from them:

It is not clear from the post what mode they want to operate the device in, PCI or USB? They say they have confirmed it is operating in PCI implying that they want it to enumerate in USB mode, if this is the case the first thing they need to check is that they are driving pin 20 high when the device is powered up, this will force it into USB mode.

If you wish, we would be happy to facilitate an introduction to Semtech/Sierra for direct communication.

Best regards,
Collin

4

Hi @collin.tx,

Thanks for your reply and the information. We try to get the modem running in PCI mode, which is the default operating mode for this modem.

Can you confirm whether Toradex engineers have worked with this modem before?
Other than that, is there an alternative 5G modem supported with Toradex (other than the ones listed in the compatibility list (i.e., Fibocom FM-160)?
If possible, getting in touch with Semtech is an alternative indeed.

Thanks,
Simon