stm32g0: add fdcan2 in dts file

[adri1mart1]

Hello,

Following my recent opened discussion, I have tried to deal with the dual can controller of the stm32g0.

Right now, it is not supported, however, it seems very small changes are needed to make it work.

STM32G0 shares the same interrupt line for both its CAN controllers and about a year ago, the shared interrupt line had been added (see shared interrupt PR)

Another interesting information is about the driver itself, the can_stm32_fdcan.c implements a macro to generate fdcan instances based on all enabled fdcan controller nodes in dts that are with a status okay (see macro).

So on my side, i've just added the fdcan2 for the stm32g0 in the stm32g0b1.dtsi and also on the nucleo_g0b1re board with appropriate pinout.

To test my setup, I have used the nucleo_g0b1re board with 2 external transceivers on a breadboard to set up a communication between fdcan1 and fdcan2. I used a PEAK CAN probe to check frames are well physically transferred from one to another.
I have tested only fdcan1, then only fdcan2, then both, it seems to work great !

Right now, there is no sample program from zephyr ready to go with this configuration so I had to update the counter example for my needs and I'm definitely not sure it is absolutely needed.

Important note on this modification. In the nucleo_g0b1re dts file, I have added the fdcan2 node with the correct pinout. However, fdcan2 is disabled by default whereas fdcan1 is enabled.

If you enable fdcan1 and fdcan2, you will get this error:

[151/155] Generating isr_tables.c
FAILED: zephyr/isr_tables.c .../build/zephyr/isr_tables.c 
[...]
gen_isr_tables.py: error: multiple registrations at table_index 22 for irq 22 (0x16)
Existing handler 0x8009c8b, new handler 0x8009c8b
Has IRQ_CONNECT or IRQ_DIRECT_CONNECT accidentally been invoked on the same irq multiple times?

You must add the CONFIG_SHARED_INTERRUPT=y flag to make it work. This could be confusing for anyone who is not familiar with the fact that stm32g0 fdcan controller is concerned about shared interrupt.

I am not sure if the zephyr community wants to live with it, improve the comment above when the error is raised, add a specific paragraph in the nucleo_g0b1re doc page. Any feedback will be very appreciated.

Regards,
Adrien M.

[github-actions]

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[henrikbrixandersen]

@erwan Do you know if all compatible = "st,stm32-fdcan" instances across the STM32 use shared interrupts?

If so, we need to automatically enable shared IRQs on the driver Kconfig level. If not, we need to enable it on SoC Kconfig level. Regardless of which it is, we'll likely need a new Kconfig function for checking the number of status=okay nodes with a given compatible.

[erwango]

@henrikbrixandersen From what I can see, only stm32g0b1 and stm32g0c1 provide FDCAN, but both would require shared interrupts.

[henrikbrixandersen]

@henrikbrixandersen From what I can see, only stm32g0b1 and stm32g0c1 provide FDCAN, but both would require shared interrupts.

Thanks. Based on that, I'd like to see something like the following added to this PR:

diff --git a/soc/arm/st_stm32/stm32g0/Kconfig.defconfig.stm32g0b1xx b/soc/arm/st_stm32/stm32g0/Kconfig.defconfig.stm32g0b1xx
index 86c47b158e..05d2116225 100644
--- a/soc/arm/st_stm32/stm32g0/Kconfig.defconfig.stm32g0b1xx
+++ b/soc/arm/st_stm32/stm32g0/Kconfig.defconfig.stm32g0b1xx
@@ -11,4 +11,7 @@ config SOC
 config NUM_IRQS
        default 31
 
+config SHARED_INTERRUPTS
+       default y if $(dt_nodelabel_enabled,fdcan1) && $(dt_nodelabel_enabled,fdcan2)
+
 endif # SOC_STM32G0B1XX

[henrikbrixandersen]

Okay, sounds good. Please split this into two commits, though. One for the SoC+DTS, one for the board.

[adri1mart1]

Done on my side

[erwango]

Please update nucleo_g0b1re.yaml file to mention it supports can.
Aim is that it could be automatically compiled/tested in CI.
Otherwise LGTM, thanks for this contribution

[erwango]

Approved as I don't want to be picky, but still advise use of depends on FOO when only one symbol is impacted (while if FOO should be reserved when more than one are impacted by the condition).

[github-actions]

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