linux-kernel - [PATCH 4.14 170/496] clocksource/drivers/mips-gic-timer: Use correct shift count to extract data

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Date:   Mon, 28 May 2018 11:59:15 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Felix Fietkau <nbd@....name>,
        Thomas Gleixner <tglx@...utronix.de>,
        daniel.lezcano@...aro.org, paul.burton@...tec.com,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 4.14 170/496] clocksource/drivers/mips-gic-timer: Use correct shift count to extract data

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Felix Fietkau <nbd@....name>

[ Upstream commit 5753405e27f8fe4c42c1537d3ddbd9e058e54cdc ]

__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
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/clocksource/mips-gic-timer.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/clocksource/mips-gic-timer.c
+++ b/drivers/clocksource/mips-gic-timer.c
@@ -164,7 +164,7 @@ static int __init __gic_clocksource_init
 
 	/* 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);