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| author | Rasmus Villemoes <linux@rasmusvillemoes.dk> | 2019-10-04 16:32:06 +0300 |
|---|---|---|
| committer | Thierry Reding <thierry.reding@gmail.com> | 2020-01-08 15:35:12 +0300 |
| commit | 3c64ed74d619c25c65abb1fcafcb1aff835867d5 (patch) | |
| tree | ae8772eeac8e186dbc916dcfef04a2fae3fc77b1 | |
| parent | 366486e0afaa115ec456db124fc07d824a1c1fb1 (diff) | |
| download | linux-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.c | 6 |
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) |