drivers: can: stm32: fix bus-speed

[jdascenzio]

Set the prescaler in register BTR according to the configured bitrate in DTS.
This bug appeared in commit 8b6c1bd

Signed-off-by: Julien D'Ascenzio [email protected]

[martinjaeger]

Thanks for that fix, which provides a partial solution for #31150 aswell. Just got a small change request.

[erwango]

Approved from testing point of view. tests/subsys/canbus/isotp/conformance is now passed (and the MPU FAULT went away, even if not related)

[alexanderwachter]

The rest looks good!
Hanks for this fix. I wonder why I didn't catch the bug in my tests 🤔

[erwango]

@martinjaeger @alexanderwachter can we state: fixes #31150 ?
Or do you expect another fix ?

[martinjaeger]

@martinjaeger @alexanderwachter can we state: fixes #31150 ?
Or do you expect another fix ?

For me it does not completely fix the isotp/conformance test, so there must be another bug. I still get a hard fault on nucleo_l452re:

*** Booting Zephyr OS build zephyr-v2.4.0-2839-g4b7eb0500dbf  ***
Running test suite isotp_conformance
===================================================================
START - test_send_sf
E: ***** HARD FAULT *****
E: r0/a1:  0x20001068  r1/a2:  0x2000109c  r2/a3:  0x00000008
E: r3/a4:  0x000000f9 r12/ip:  0x00000000 r14/lr:  0x08000be1
E:  xpsr:  0x21000000
E: Faulting instruction address (r15/pc): 0x08000b10
E: >>> ZEPHYR FATAL ERROR 0: CPU exception on CPU 0
E: Current thread: 0x20000498 (ztest_thread)
E: Halting system