[RFC PATCH v2 0/4] can: bxcan: add support for ST bxCAN controller

[Dario Binacchi <dario.binacchi@amarulasolutions.com>]

The series adds support for the basic extended CAN controller (bxCAN)
found in many low- to middle-end STM32 SoCs.

The driver design (one core module and one driver module) was inspired
by other ST drivers (e. g. drivers/iio/adc/stm32-adc.c,
drivers/iio/adc/stm32-adc-core.c) where device instances share resources.
The shared resources functions are implemented in the core module, the
device driver in a separate module.

The driver has been tested on the stm32f469i-discovery board with a
kernel version 5.19.0-rc2 in loopback + silent mode:

ip link set can0 type can bitrate 125000 loopback on listen-only on
ip link set up can0
candump can0 -L &
cansend can0 300#AC.AB.AD.AE.75.49.AD.D1

For uboot and kernel compilation, as well as for rootfs creation I used
buildroot:

make stm32f469_disco_sd_defconfig
make

but I had to patch can-utils and busybox as can-utils and iproute are
not compiled for MMU-less microcotrollers. In the case of can-utils,
replacing the calls to fork() with vfork(), I was able to compile the
package with working candump and cansend applications, while in the
case of iproute, I ran into more than one problem and finally I decided
to extend busybox's ip link command for CAN-type devices. I'm still
wondering if it was really necessary, but this way I was able to test
the driver.

Changes in v2:
- Change the file name into 'st,stm32-bxcan-core.yaml'.
- Rename compatibles:
  - st,stm32-bxcan-core -> st,stm32f4-bxcan-core
  - st,stm32-bxcan -> st,stm32f4-bxcan
- Rename master property to st,can-master.
- Remove the status property from the example.
- Put the node child properties as required.
- Remove a blank line.
- Fix sparse errors.
- Create a MAINTAINERS entry.
- Remove the print of the registers address.
- Remove the volatile keyword from bxcan_rmw().
- Use tx ring algorithm to manage tx mailboxes.
- Use can_{get|put}_echo_skb().
- Update DT properties.

Dario Binacchi (4):
  dt-bindings: net: can: add STM32 bxcan DT bindings
  ARM: dts: stm32: add CAN support on stm32f429
  ARM: dts: stm32: add pin map for CAN controller on stm32f4
  can: bxcan: add support for ST bxCAN controller

 .../bindings/net/can/st,stm32-bxcan.yaml      |  136 +++
 MAINTAINERS                                   |    7 +
 arch/arm/boot/dts/stm32f4-pinctrl.dtsi        |   31 +
 arch/arm/boot/dts/stm32f429.dtsi              |   30 +
 drivers/net/can/Kconfig                       |    1 +
 drivers/net/can/Makefile                      |    1 +
 drivers/net/can/bxcan/Kconfig                 |   34 +
 drivers/net/can/bxcan/Makefile                |    4 +
 drivers/net/can/bxcan/bxcan-core.c            |  200 ++++
 drivers/net/can/bxcan/bxcan-core.h            |   33 +
 drivers/net/can/bxcan/bxcan-drv.c             | 1043 +++++++++++++++++
 11 files changed, 1520 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/net/can/st,stm32-bxcan.yaml
 create mode 100644 drivers/net/can/bxcan/Kconfig
 create mode 100644 drivers/net/can/bxcan/Makefile
 create mode 100644 drivers/net/can/bxcan/bxcan-core.c
 create mode 100644 drivers/net/can/bxcan/bxcan-core.h
 create mode 100644 drivers/net/can/bxcan/bxcan-drv.c

-- 
2.32.0