Messages in this thread | | | Subject | Re: [PATCH] powerpc/time: use feature fixup in __USE_RTC() instead of cpu feature. | From | Christophe Leroy <> | Date | Mon, 26 Aug 2019 13:48:41 +0200 |
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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.
> > 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 ?
Christophe
> > cheers > >> diff --git a/arch/powerpc/include/asm/time.h b/arch/powerpc/include/asm/time.h >> index 54f4ec1f9fab..3455cb54c333 100644 >> --- a/arch/powerpc/include/asm/time.h >> +++ b/arch/powerpc/include/asm/time.h >> @@ -42,7 +42,14 @@ struct div_result { >> /* Accessor functions for the timebase (RTC on 601) registers. */ >> /* If one day CONFIG_POWER is added just define __USE_RTC as 1 */ >> #ifdef CONFIG_PPC_BOOK3S_32 >> -#define __USE_RTC() (cpu_has_feature(CPU_FTR_USE_RTC)) >> +static inline bool __USE_RTC(void) >> +{ >> + asm_volatile_goto(ASM_FTR_IFCLR("nop;", "b %1;", %0) :: >> + "i" (CPU_FTR_USE_RTC) :: l_use_rtc); >> + return false; >> +l_use_rtc: >> + return true; >> +} >> #else >> #define __USE_RTC() 0 >> #endif >> -- >> 2.13.3
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