Commit 21a0ffd9 authored Nov 27, 2021 by Stephan Gerhold Committed by David S. Miller Nov 29, 2021

net: wwan: Add Qualcomm BAM-DMUX WWAN network driver



The BAM Data Multiplexer provides access to the network data channels of
modems integrated into many older Qualcomm SoCs, e.g. Qualcomm MSM8916 or
MSM8974. It is built using a simple protocol layer on top of a DMA engine
(Qualcomm BAM) and bidirectional interrupts to coordinate power control.

The modem announces a fixed set of channels by sending an OPEN command.
The driver exports each channel as separate network interface so that
a connection can be established via QMI from userspace. The network
interface can work either in Ethernet or Raw-IP mode (configurable via
QMI). However, Ethernet mode seems to be broken with most firmwares
(network packets are actually received as Raw-IP), therefore the driver
only supports Raw-IP mode.

Note that the control channel (QMI/AT) is entirely separate from
BAM-DMUX and is already supported by the RPMSG_WWAN_CTRL driver.

The driver uses runtime PM to coordinate power control with the modem.
TX/RX buffers are put in a kind of "ring queue" and submitted via
the bam_dma driver of the DMAEngine subsystem.

The basic architecture looks roughly like this:

                   +------------+                +-------+
         [IPv4/6]  |  BAM-DMUX  |                |       |
         [Data...] |            |                |       |
        ---------->|wwan0       | [DMUX chan: x] |       |
         [IPv4/6]  | (chan: 0)  | [IPv4/6]       |       |
         [Data...] |            | [Data...]      |       |
        ---------->|wwan1       |--------------->| Modem |
                   | (chan: 1)  |      BAM       |       |
         [IPv4/6]  | ...        |  (DMA Engine)  |       |
         [Data...] |            |                |       |
        ---------->|wwan7       |                |       |
                   | (chan: 7)  |                |       |
                   +------------+                +-------+

Note that some newer firmware versions support QMAP ("rmnet" driver)
as additional multiplexing layer on top of BAM-DMUX, but this is not
currently supported by this driver.

Signed-off-by: Stephan Gerhold <stephan@gerhold.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent f3aee7c9

MAINTAINERS

+8 −0

Original line number	Diff line number	Diff line
		@@ -15727,6 +15727,14 @@ W: https://wireless.wiki.kernel.org/en/users/Drivers/ath9k
		F: Documentation/devicetree/bindings/net/wireless/qca,ath9k.yaml
		F: drivers/net/wireless/ath/ath9k/

		QUALCOMM BAM-DMUX WWAN NETWORK DRIVER
		M: Stephan Gerhold <stephan@gerhold.net>
		L: netdev@vger.kernel.org
		L: linux-arm-msm@vger.kernel.org
		S: Maintained
		F: Documentation/devicetree/bindings/net/qcom,bam-dmux.yaml
		F: drivers/net/wwan/qcom_bam_dmux.c

		QUALCOMM CAMERA SUBSYSTEM DRIVER
		M: Robert Foss <robert.foss@linaro.org>
		M: Todor Tomov <todor.too@gmail.com>

drivers/net/wwan/Kconfig

+13 −0

Original line number	Diff line number	Diff line
		@@ -50,6 +50,19 @@ config MHI_WWAN_MBIM
		To compile this driver as a module, choose M here: the module will be
		called mhi_wwan_mbim.

		config QCOM_BAM_DMUX
		tristate "Qualcomm BAM-DMUX WWAN network driver"
		depends on (DMA_ENGINE && PM && QCOM_SMEM_STATE) \|\| COMPILE_TEST
		help
		The BAM Data Multiplexer provides access to the network data channels
		of modems integrated into many older Qualcomm SoCs, e.g. Qualcomm
		MSM8916 or MSM8974. The connection can be established via QMI/AT from
		userspace with control ports available through the WWAN subsystem
		(CONFIG_RPMSG_WWAN_CTRL) or QRTR network sockets (CONFIG_QRTR).

		To compile this driver as a module, choose M here: the module will be
		called qcom_bam_dmux.

		config RPMSG_WWAN_CTRL
		tristate "RPMSG WWAN control driver"
		depends on RPMSG

drivers/net/wwan/Makefile

+1 −0

Original line number	Diff line number	Diff line
		@@ -10,5 +10,6 @@ obj-$(CONFIG_WWAN_HWSIM) += wwan_hwsim.o

		obj-$(CONFIG_MHI_WWAN_CTRL) += mhi_wwan_ctrl.o
		obj-$(CONFIG_MHI_WWAN_MBIM) += mhi_wwan_mbim.o
		obj-$(CONFIG_QCOM_BAM_DMUX) += qcom_bam_dmux.o
		obj-$(CONFIG_RPMSG_WWAN_CTRL) += rpmsg_wwan_ctrl.o
		obj-$(CONFIG_IOSM) += iosm/

drivers/net/wwan/qcom_bam_dmux.c

0 → 100644

+907 −0

File added.

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