linux-kernel - [tip:timers/urgent] clocksource/drivers/mips-gic-timer: Use correct shift count to extract data

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Message-ID: <tip-5753405e27f8fe4c42c1537d3ddbd9e058e54cdc@git.kernel.org>
Date:   Wed, 28 Feb 2018 04:58:56 -0800
From:   tip-bot for Felix Fietkau <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     tglx@...utronix.de, nbd@....name, mingo@...nel.org,
        linux-kernel@...r.kernel.org, hpa@...or.com
Subject: [tip:timers/urgent] clocksource/drivers/mips-gic-timer: Use correct
 shift count to extract data

Commit-ID:  5753405e27f8fe4c42c1537d3ddbd9e058e54cdc
Gitweb:     https://git.kernel.org/tip/5753405e27f8fe4c42c1537d3ddbd9e058e54cdc
Author:     Felix Fietkau <nbd@....name>
AuthorDate: Wed, 28 Feb 2018 10:56:10 +0100
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Wed, 28 Feb 2018 13:55:14 +0100

clocksource/drivers/mips-gic-timer: Use correct shift count to extract data

__gic_clocksource_init() extracts the GIC_CONFIG_COUNTBITS field from
read_gic_config() by right shifting the register value. The shift count is
determined by the most significant bit (__fls) of the bitmask which is
wrong as it shifts out the complete bitfield.

Use the least significant bit (__ffs) instead to shift the bitfield down to
bit 0.

Fixes: e07127a077c7 ("clocksource: mips-gic-timer: Use new GIC accessor functions")
Signed-off-by: Felix Fietkau <nbd@....name>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: daniel.lezcano@...aro.org
Cc: paul.burton@...tec.com
Link: https://lkml.kernel.org/r/20180228095610.50341-1-nbd@nbd.name

---
 drivers/clocksource/mips-gic-timer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/clocksource/mips-gic-timer.c b/drivers/clocksource/mips-gic-timer.c
index 65e18c86d9b9..986b6796b631 100644
--- a/drivers/clocksource/mips-gic-timer.c
+++ b/drivers/clocksource/mips-gic-timer.c
@@ -166,7 +166,7 @@ static int __init __gic_clocksource_init(void)
 
 	/* Set clocksource mask. */
 	count_width = read_gic_config() & GIC_CONFIG_COUNTBITS;
-	count_width >>= __fls(GIC_CONFIG_COUNTBITS);
+	count_width >>= __ffs(GIC_CONFIG_COUNTBITS);
 	count_width *= 4;
 	count_width += 32;
 	gic_clocksource.mask = CLOCKSOURCE_MASK(count_width);