From: Thomas Gleixner <tglx@linutronix.de>
Date: Mon, 4 Apr 2022 14:47:55 +0000 (+0200)
Subject: timers: Simplify calc_index()
X-Git-Tag: v6.1-rc5~1125^2~13
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=a2026e44eff5d74a83d7ffee6325a007bef85385;p=platform%2Fkernel%2Flinux-starfive.git

timers: Simplify calc_index()

The level granularity round up of calc_index() does:

   (x + (1 << n)) >> n

which is obviously equivalent to

   (x >> n) + 1

but compilers can't figure that out despite the fact that the input range
is known to not cause an overflow. It's neither intuitive to read.

Just write out the obvious.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/87h778j46c.ffs@tglx
---

diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 204d6cd..60aebf2 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -502,7 +502,7 @@ static inline unsigned calc_index(unsigned long expires, unsigned lvl,
 	 *
 	 * Round up with level granularity to prevent this.
 	 */
-	expires = (expires + LVL_GRAN(lvl)) >> LVL_SHIFT(lvl);
+	expires = (expires >> LVL_SHIFT(lvl)) + 1;
 	*bucket_expiry = expires << LVL_SHIFT(lvl);
 	return LVL_OFFS(lvl) + (expires & LVL_MASK);
 }