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

[ 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@nbd.name>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: daniel.lezcano@linaro.org
Cc: paul.burton@imgtec.com
Link: https://lkml.kernel.org/r/20180228095610.50341-1-nbd@nbd.name
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/clocksource/mips-gic-timer.c b/drivers/clocksource/mips-gic-timer.c
index ae3167c28b129b6c3d3cc0fbc5c4a0da1a9abacd..a07f51231e335029a2ff2726092f8570c3b81a9d 100644 (file)
--- a/drivers/clocksource/mips-gic-timer.c
+++ b/drivers/clocksource/mips-gic-timer.c
@@ -164,7 +164,7 @@ 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);