linux-kernel - [PATCH v2] clocksource: Use GENMASK_ULL in definition of CLOCKSOURCE

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Date:   Mon, 17 Apr 2017 10:38:59 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     John Stultz <john.stultz@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-kernel@...r.kernel.org, Dmitry Torokhov <dtor@...omium.org>,
        Grant Grundler <grundler@...omium.org>,
        Greg Hackmann <ghackmann@...gle.com>,
        Michael Davidson <md@...gle.com>,
        Matthias Kaehlcke <mka@...omium.org>
Subject: [PATCH v2] clocksource: Use GENMASK_ULL in definition of CLOCKSOURCE_MASK

Besides reusing existing code this removes the special case handling
for 64-bit masks, which causes clang to raise a shift count overflow
warning due to https://bugs.llvm.org//show_bug.cgi?id=10030.

Suggested-by: Dmitry Torokhov <dtor@...omium.org>
Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
---
Changes in v2:
- Remove unnecessary cast to u64

 include/linux/clocksource.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
index cfc75848a35d..f2b10d9ebd04 100644
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h
@@ -120,7 +120,7 @@ struct clocksource {
#define CLOCK_SOURCE_RESELECT			0x100
 
 /* simplify initialization of mask field */
-#define CLOCKSOURCE_MASK(bits) (u64)((bits) < 64 ? ((1ULL<<(bits))-1) : -1)
+#define CLOCKSOURCE_MASK(bits) GENMASK_ULL((bits) - 1, 0)
 
 static inline u32 clocksource_freq2mult(u32 freq, u32 shift_constant, u64 from)
 {
-- 
2.12.2.762.g0e3151a226-goog