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Subject[RFC PATCH v3 12/12] powerpc/vdso: provide __arch_is_hw_counter_valid()
Date
To avoid a double verification of the hw_counter validity,
provide __arch_is_hw_counter_valid()

Before:
clock-gettime-realtime: vdso: 1078 nsec/call

After:
clock-gettime-realtime: vdso: 1064 nsec/call

The * shows the test of the clock type.
The > shows the additional test on the counter,
that goes away with this patch

Before:
5e0: 81 25 00 04 lwz r9,4(r5)
*5e4: 2f 89 00 00 cmpwi cr7,r9,0
*5e8: 40 9e 01 3c bne cr7,724 <__c_kernel_clock_gettime+0x17c>
5ec: 94 21 ff e0 stwu r1,-32(r1)
5f0: 93 61 00 0c stw r27,12(r1)
5f4: 93 81 00 10 stw r28,16(r1)
5f8: 93 a1 00 14 stw r29,20(r1)
5fc: 93 c1 00 18 stw r30,24(r1)
600: 93 e1 00 1c stw r31,28(r1)
604: 7d 8d 42 e6 mftbu r12
608: 7f ac 42 e6 mftb r29
60c: 7c cd 42 e6 mftbu r6
610: 7f 8c 30 40 cmplw cr7,r12,r6
614: 40 9e ff f0 bne cr7,604 <__c_kernel_clock_gettime+0x5c>
>618: 2f 8c 00 00 cmpwi cr7,r12,0
61c: 83 6b 00 28 lwz r27,40(r11)
620: 83 8b 00 2c lwz r28,44(r11)
624: 81 45 00 08 lwz r10,8(r5)
628: 80 e5 00 0c lwz r7,12(r5)
>62c: 41 9c 00 b4 blt cr7,6e0 <__c_kernel_clock_gettime+0x138>
630: 81 05 00 18 lwz r8,24(r5)
634: 83 c5 00 1c lwz r30,28(r5)
638: 80 cb 00 24 lwz r6,36(r11)
63c: 83 e5 00 00 lwz r31,0(r5)
640: 7f 9f 00 40 cmplw cr7,r31,r0
644: 40 9e 00 84 bne cr7,6c8 <__c_kernel_clock_gettime+0x120>

After:
5e0: 81 25 00 04 lwz r9,4(r5)
*5e4: 2f 89 00 00 cmpwi cr7,r9,0
*5e8: 40 9e 01 88 bne cr7,770 <__c_kernel_clock_gettime+0x1c8>
5ec: 94 21 ff e0 stwu r1,-32(r1)
5f0: 93 61 00 0c stw r27,12(r1)
5f4: 93 81 00 10 stw r28,16(r1)
5f8: 93 a1 00 14 stw r29,20(r1)
5fc: 93 c1 00 18 stw r30,24(r1)
600: 93 e1 00 1c stw r31,28(r1)
604: 7f cd 42 e6 mftbu r30
608: 7f ac 42 e6 mftb r29
60c: 7c cd 42 e6 mftbu r6
610: 7f 9e 30 40 cmplw cr7,r30,r6
614: 40 9e ff f0 bne cr7,604 <__c_kernel_clock_gettime+0x5c>
618: 83 6b 00 28 lwz r27,40(r11)
61c: 83 8b 00 2c lwz r28,44(r11)
620: 81 45 00 08 lwz r10,8(r5)
624: 80 e5 00 0c lwz r7,12(r5)
628: 81 05 00 18 lwz r8,24(r5)
62c: 83 e5 00 1c lwz r31,28(r5)
630: 80 cb 00 24 lwz r6,36(r11)
634: 81 85 00 00 lwz r12,0(r5)
638: 7f 8c 00 40 cmplw cr7,r12,r0
63c: 40 9e 00 84 bne cr7,6c0 <__c_kernel_clock_gettime+0x118>

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
arch/powerpc/include/asm/vdso/gettimeofday.h | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/include/asm/vdso/gettimeofday.h b/arch/powerpc/include/asm/vdso/gettimeofday.h
index d1e702e0ea86..c5a24f31382e 100644
--- a/arch/powerpc/include/asm/vdso/gettimeofday.h
+++ b/arch/powerpc/include/asm/vdso/gettimeofday.h
@@ -69,15 +69,18 @@ int clock_getres32_fallback(clockid_t _clkid, struct old_timespec32 *_ts)
}
#endif

-static __always_inline u64 __arch_get_hw_counter(s32 clock_mode)
+static __always_inline bool __arch_is_hw_counter_valid(s32 clock_mode)
{
/*
* clock_mode == 0 implies that vDSO are enabled otherwise
* fallback on syscall.
*/
- if (clock_mode != 0)
- return U64_MAX;
+ return clock_mode == 0 ? true : false;
+}
+#define __arch_is_hw_counter_valid __arch_is_hw_counter_valid

+static __always_inline u64 __arch_get_hw_counter(s32 clock_mode)
+{
return get_tb();
}

--
2.13.3
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