Messages in this thread Patch in this message | | | Subject | Re: [PATCH] powerpc/time: use feature fixup in __USE_RTC() instead of cpu feature. | From | Christophe Leroy <> | Date | Mon, 26 Aug 2019 15:40:07 +0200 |
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Le 26/08/2019 à 15:25, Benjamin Herrenschmidt a écrit : > On Mon, 2019-08-26 at 21:41 +1000, Michael Ellerman wrote: >> 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. >> >> 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. > > Didn't we ditch 601 support years ago anyway ? We had workaround we > threw out I think...
There are still workarounds for 601 in the kernel, for exemple (in arch/powerpc/include/asm/ppc_asm.h)
/* various errata or part fixups */ #ifdef CONFIG_PPC601_SYNC_FIX #define SYNC \ BEGIN_FTR_SECTION \ sync; \ isync; \ END_FTR_SECTION_IFSET(CPU_FTR_601) #define SYNC_601 \ BEGIN_FTR_SECTION \ sync; \ END_FTR_SECTION_IFSET(CPU_FTR_601) #define ISYNC_601 \ BEGIN_FTR_SECTION \ isync; \ END_FTR_SECTION_IFSET(CPU_FTR_601) #else #define SYNC #define SYNC_601 #define ISYNC_601 #endif
But if you think we can get rid of 601 completely, I'm happy with that.
Christophe
> > Cheers, > Ben. > >> 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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