reset on mpc83xx
rasmus.villemoes at prevas.dk
Thu Apr 30 16:44:19 CEST 2020
I'm wondering why the sysreset_mpc83xx driver (as well as the similar
code in arch/powerpc/cpu/mpc83xx/cpu.c) removes the MSR_IR and MSR_DR
bits from MSR.
On my mpc8309, that seems to simply make the board hang right after
writing the new MSR value - i.e., it never gets to write the magic value
0x52535445 to RPR and of course not to then actually do the reset.
- msr &= ~(MSR_EE | MSR_IR | MSR_DR);
+ msr &= ~(MSR_EE);
(whether using the sysreset driver or the cpu.c code) makes the board
reset as expected.
The linux kernel's mpc83xx_restart() doesn't seem to remove those bits,
and rebooting from linux works as expected - it does local_irq_disable()
which amounts to clearing the EE bit.
But since the arch/powerpc/cpu/mpc83xx/cpu.c code in U-Boot has been
there forever, I assume I'm missing something fundamental.
[The board happens to have an external watchdog circuit that performs a
power cycle after a while, but there are cases, e.g. bootstrapping,
where that circuitry is disabled, and moreover, we'd like to be able to
make use of the reset status register to distinguish a reset from a cold
More information about the U-Boot