linux-kernel - [RFC PATCH v4 09/11] powerpc/vdso: override __arch_vdso

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Message-Id: <2bf9735a6ae5ff9b350b667c0b8434cf2bbe9b50.1579196675.git.christophe.leroy@c-s.fr>
Date:   Thu, 16 Jan 2020 17:58:33 +0000 (UTC)
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>, nathanl@...ux.ibm.com,
        arnd@...db.de, tglx@...utronix.de, vincenzo.frascino@....com,
        luto@...nel.org
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-arm-kernel@...ts.infradead.org, linux-mips@...r.kernel.org,
        x86@...nel.org
Subject: [RFC PATCH v4 09/11] powerpc/vdso: override __arch_vdso_capable()

When the timebase is used, make __arch_vdso_capable() always
return true. When the RTC clock is used, make __arch_vdso_capable()
always return false.

Before the patch:
clock-gettime-realtime:    vdso: 1086 nsec/call

After the patch:
clock-gettime-realtime:    vdso: 1033 nsec/call

Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
---
 arch/powerpc/include/asm/vdso/gettimeofday.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/powerpc/include/asm/vdso/gettimeofday.h b/arch/powerpc/include/asm/vdso/gettimeofday.h
index 0a247f9b9af9..74b6eef8fbe9 100644
--- a/arch/powerpc/include/asm/vdso/gettimeofday.h
+++ b/arch/powerpc/include/asm/vdso/gettimeofday.h
@@ -74,6 +74,12 @@ static __always_inline u64 __arch_get_hw_counter(s32 clock_mode)
 
 const struct vdso_data *__arch_get_vdso_data(void);
 
+static inline bool __arch_vdso_capable(const struct vdso_data *vd)
+{
+	return !__USE_RTC();
+}
+#define __arch_vdso_capable __arch_vdso_capable
+
 /*
  * powerpc specific delta calculation.
  *
-- 
2.13.3