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authorRasmus Villemoes <linux@rasmusvillemoes.dk>2019-10-04 16:32:06 +0300
committerThierry Reding <thierry.reding@gmail.com>2020-01-08 15:35:12 +0300
commit3c64ed74d619c25c65abb1fcafcb1aff835867d5 (patch)
treeae8772eeac8e186dbc916dcfef04a2fae3fc77b1
parent366486e0afaa115ec456db124fc07d824a1c1fb1 (diff)
downloadlinux-3c64ed74d619c25c65abb1fcafcb1aff835867d5.tar.xz
pwm: mxs: Avoid a division in mxs_pwm_apply()
Since the divisor is not a compile-time constant (unless gcc somehow decided to unroll the loop PERIOD_CDIV_MAX times), this does a somewhat expensive 32/32 division. Replace that with a right shift. We still have a 64/32 division just below, but at least in that case the divisor is compile-time constant. Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk> Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
-rw-r--r--drivers/pwm/pwm-mxs.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/drivers/pwm/pwm-mxs.c b/drivers/pwm/pwm-mxs.c
index 57562221c439..f2e57fcf8f8b 100644
--- a/drivers/pwm/pwm-mxs.c
+++ b/drivers/pwm/pwm-mxs.c
@@ -33,8 +33,8 @@
#define PERIOD_CDIV(div) (((div) & 0x7) << 20)
#define PERIOD_CDIV_MAX 8
-static const unsigned int cdiv[PERIOD_CDIV_MAX] = {
- 1, 2, 4, 8, 16, 64, 256, 1024
+static const u8 cdiv_shift[PERIOD_CDIV_MAX] = {
+ 0, 1, 2, 3, 4, 6, 8, 10
};
struct mxs_pwm_chip {
@@ -71,7 +71,7 @@ static int mxs_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
rate = clk_get_rate(mxs->clk);
while (1) {
- c = rate / cdiv[div];
+ c = rate >> cdiv_shift[div];
c = c * state->period;
do_div(c, 1000000000);
if (c < PERIOD_PERIOD_MAX)