Messages in this thread | | | From | Michael Ellerman <> | Subject | Re: [PATCH] powerpc/time: use feature fixup in __USE_RTC() instead of cpu feature. | Date | Tue, 27 Aug 2019 12:13:51 +1000 |
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Christophe Leroy <christophe.leroy@c-s.fr> writes: > Le 26/08/2019 à 13:41, Michael Ellerman a écrit : >> Christophe Leroy <christophe.leroy@c-s.fr> writes: >>> sched_clock(), used by printk(), calls __USE_RTC() to know >>> whether to use realtime clock or timebase. >>> >>> __USE_RTC() uses cpu_has_feature() which is initialised by >>> machine_init(). Before machine_init(), __USE_RTC() returns true, >>> leading to a program check exception on CPUs not having realtime >>> clock. >>> >>> In order to be able to use printk() earlier, use feature fixup. >>> Feature fixups are applies in early_init(), enabling the use of >>> printk() earlier. >>> >>> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr> >>> --- >>> arch/powerpc/include/asm/time.h | 9 ++++++++- >>> 1 file changed, 8 insertions(+), 1 deletion(-) >> >> The other option would be just to make this a compile time decision, eg. >> add CONFIG_PPC_601 and use that to gate whether we use RTC. > > Euh ... yes OK, why not. And that would help simplify many places in the > code. I can propose something in that direction, but it will be a bigger > change.
Thanks.
>> Given how many 601 users there are, maybe 1?, I think that would be a >> simpler option and avoids complicating the code / binary for everyone >> else. > > However this patch doesn't complicate things more than it was with > cpu_has_feature() which does exactly the same but using static keys, > does it ?
It's more complicated in that it's not using cpu_has_feature() it's doing some custom thing that is not used anywhere else. But yeah I guess it's not much extra complication.
cheers
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