PCIE mode in new 5G modems

[Loic Poulain]

Hi Bruno,

On Thu, 28 Oct 2021 at 13:13, Bruno Antunes <baantunes at gmail.com> wrote:
>
> Hi Aleksander,
>
> Thank you for the prompt reply.
>
> On Wed, 27 Oct 2021 at 08:30, Aleksander Morgado
> <aleksander at aleksander.es> wrote:
> >
> > Hey Bruno,
> >
> > > Has anyone tried the PCIE mode on the newer 5G modems?
> >
> > Yes yes, I use one almost everyday in my laptop.
> >
> > > I have tested with both the Quectel RM500Q and the SIMCom 8202G with
no success.
> > > The Quectel model is detected by the modemmanager but can't establish
> > > a connection:
> > >
> > >
> > > mmcli -V
> > > mmcli 1.17.900
> > >
> > > mmcli -L
> > >     /org/freedesktop/ModemManager1/Modem/1 [manufacturer unknown]
model unknown
> > >     /org/freedesktop/ModemManager1/Modem/0 [Quectel] RM500Q-GL
>
> This is the output from a single Quectel modem.
> We cannot fully disable the USB mode, that is why the modem manager
> detects 2 modems, one in USB mode and other in PCI.
>
> > >
> > > mmcli -m 0
> > >   -----------------------------
> > >   General  |              path: /org/freedesktop/ModemManager1/Modem/0
> > >                  |         device id:
9490a63480fa96a9c2b519059801e65adb2a9681
> > >   -----------------------------
> > >   Hardware |      manufacturer: Quectel
> > >                   |             model: RM500Q-GL
> > >                   | firmware revision: RM500QGLABR11A03M4G
> > >                   |         supported: gsm-umts, lte
> > >                   |           current: gsm-umts, lte
> > >                   |      equipment id: 863305040265935
> > >   -----------------------------
> > >   System   |            device:
> > > /sys/devices/platform/soc/3110000.usb3/xhci-hcd.1.auto/usb4/4-1/4-1.2
> >
> > The RM500 here is being detected in USB mode, not in PCI mode.
> >
> > >                  |           drivers: option
> >
> > And only used with TTYs, not being managed in either MBIM or QMI. Is
> > this a custom system that doesn't have qmi_wwan or cdc_mbim support?
>
> Maybe I wasn't clear but both outputs correspond to the same Quectel
> modem that is being detected as USB (mmcli -m 0) and PCI (mmcli -m 1).
> Probably that's why some ports are on one modem and others on the other.
>
> >
> > >                  |            plugin: quectel
> > >                  |      primary port: ttyUSB2
> > >                  |             ports: ttyUSB0 (qcdm), ttyUSB1 (gps),
> > > ttyUSB2 (at)
> > >   -----------------------------
> > >   Status   |              lock: sim-pin
> > >                |    unlock retries: sim-pin (3), sim-puk (10),
> > > sim-pin2 (3), sim-puk2 (10)
> > >                |             state: locked
> >
> > Here it says the SIM-PIN is locked; did you try to unlock it before
> > attempting the connection?
> >
> > >                |       power state: on
> > >                |    signal quality: 0% (cached)
> > >   -----------------------------
> > >   Modes    |         supported: allowed: 2g, 3g, 4g; preferred: none
> > >                  |           current: allowed: 2g, 3g, 4g; preferred:
none
> > >   -----------------------------
> > >   IP       |         supported: ipv4, ipv6, ipv4v6
> > >   -----------------------------
> > >   3GPP     |     enabled locks: sim
> > >   -----------------------------
> > >   SIM      |  primary sim path: /org/freedesktop/ModemManager1/SIM/0
> > >
> > >
> > > mmcli -m 1
> > >   -------------------------
> > >   General |           path: /org/freedesktop/ModemManager1/Modem/1
> > >   -------------------------
> > >   System  |         device:
> > >
/sys/devices/platform/soc/3400000.pcie/pci0000:00/0000:00:00.0/0000:01:00.0
> > >                 |        drivers: mhi_net, mhi-pci-generic
> >
> > This one is PCI, yes.
> >
> > >                 |         plugin: generic
> > >                 |   primary port: wwan0qmi0
> > >                 |          ports: mhi_hwip0 (net), wwan0mbim0 (mbim),
> > > wwan0qmi0 (qmi)
> >
> > And we can see both QMI and MBIM ports exposed; which is similar to the
EM9191.

Output looks fine, but it seems to bind to the generic MHI configuration
which may not be suitable for Quectel, AFAIK Quectel usually rely on MBIM
for both control/data path and you may need to configure the driver for
that. Can you check if the device has subvendor PCI IDs?

Then you can add a new entry in:
https://github.com/torvalds/linux/blob/cc0356d6a02e064387c16a83cb96fe43ef33181e/drivers/bus/mhi/pci_generic.c#L406

And point to the same config as for em1xx modems (
mhi_quectel_em1xx_channels).

Regards,
Loic
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