kernel since 5.6 do not boot anymore on Apple PowerBook

[Christophe Leroy]

Le 27/08/2020 à 16:37, Giuseppe Sacco a écrit :
> Il giorno gio, 27/08/2020 alle 12.39 +0200, Christophe Leroy ha
> scritto:
>> Hi,
>>
>> Le 27/08/2020 à 10:28, Giuseppe Sacco a écrit :
> [...]
>>> Sorry, I made a mistake. The real problem is down, on the same
>>> function, when it calls low_sleep_handler(). This is where the problem
>>> probably is.
>>
>> Great, you spotted the problem.
>>
>> I see what it is, it is in low_sleep_handler() in
>> arch/powerpc/platforms/powermac/sleep.S
>>
>> All critical registers are saved on the stack. At restore, they are
>> restore BEFORE re-enabling MMU (because they are needed for that). But
>> when we have VMAP_STACK, the stack can hardly be accessed without the
>> MMU enabled. tophys() doesn't work for virtual stack addresses.
>>
>> Therefore, the low_sleep_handler() has to be reworked for using an area
>> in the linear mem instead of the stack.
> 
> I am sorry, but I don't know how to fix it. Should I open a bug for
> tracking this problem?

Yes please, at https://github.com/linuxppc/issues/issues

In the meantime, I have sent a patch to disable CONFIG_VMAP_STACK when 
CONFIG_ADB_PMU is selected until this is fixed.

Have you tried without CONFIG_ADB_PMU ? Or does it make no sense ?

Christophe