[PATCH v4 33/40] sh: mach-x3proto: optimize ilsel_enable()

Yury Norov
2024-06-20T17:58:42Z

Simplify ilsel_enable() by using find_and_set_bit().

Geert also pointed the bug in the old implementation:

I don't think the old code worked as intended: the first time
no free bit is found, bit would have been ILSEL_LEVELS, and
test_and_set_bit() would have returned false, thus terminating
the loop, and continuing with an out-of-range bit value? Hence
to work correctly, bit ILSEL_LEVELS of ilsel_level_map should
have been initialized to one? Or am I missing something?

The new code does not have that issue.

CC: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Signed-off-by: Yury Norov <yury.norov@gmail.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
arch/sh/boards/mach-x3proto/ilsel.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/sh/boards/mach-x3proto/ilsel.c b/arch/sh/boards/mach-x3proto/ilsel.c
index f0d5eb41521a..35b585e154f0 100644
--- a/arch/sh/boards/mach-x3proto/ilsel.c
+++ b/arch/sh/boards/mach-x3proto/ilsel.c
@@ -8,6 +8,7 @@
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

+#include <linux/find_atomic.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
@@ -99,8 +100,8 @@ int ilsel_enable(ilsel_source_t set)
}

do {
- bit = find_first_zero_bit(&ilsel_level_map, ILSEL_LEVELS);
- } while (test_and_set_bit(bit, &ilsel_level_map));
+ bit = find_and_set_bit(&ilsel_level_map, ILSEL_LEVELS);
+ } while (bit >= ILSEL_LEVELS);

__ilsel_enable(set, bit);

--
2.43.0