From: Christophe Leroy <christophe.leroy@c-s.fr>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>
Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: [PATCH] powerpc/time: use feature fixup in __USE_RTC() instead of cpu feature.
Date: Mon, 26 Aug 2019 06:59:34 +0000 (UTC) [thread overview]
Message-ID: <55c267ac6e0cd289970accfafbf9dda11a324c2e.1566802736.git.christophe.leroy@c-s.fr> (raw)
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(-)
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
next reply other threads:[~2019-08-26 6:59 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-26 6:59 Christophe Leroy [this message]
2019-08-26 11:41 ` [PATCH] powerpc/time: use feature fixup in __USE_RTC() instead of cpu feature Michael Ellerman
2019-08-26 11:48 ` Christophe Leroy
2019-08-27 2:13 ` Michael Ellerman
2019-08-26 12:06 ` Segher Boessenkool
2019-08-26 13:25 ` Benjamin Herrenschmidt
2019-08-26 13:40 ` Christophe Leroy
2019-08-27 2:12 ` Michael Ellerman
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