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pwm: visconti: Fix and simplify period calculation

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With the original code a request for period = 65536000 ns and period =
32768000 ns yields the same register settings (which results in 32768000
ns) because the value for pwmc0 was miscalculated.

Also simplify using that fls(0) is 0.

Fixes: 721b595744f1 ("pwm: visconti: Add Toshiba Visconti SoC PWM support")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
This commit is contained in:
Uwe Kleine-König 2021-04-26 17:03:50 +02:00 committed by Thierry Reding
parent e9fdf122cf
commit 937efa29e7
1 changed files with 7 additions and 10 deletions
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17
drivers/pwm/pwm-visconti.c
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@ -82,17 +82,14 @@ static int visconti_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
return -ERANGE;
/*
* PWMC controls a divider that divides the input clk by a
* power of two between 1 and 8. As a smaller divider yields
* higher precision, pick the smallest possible one.
* PWMC controls a divider that divides the input clk by a power of two
* between 1 and 8. As a smaller divider yields higher precision, pick
* the smallest possible one. As period is at most 0xffff << 3, pwmc0 is
* in the intended range [0..3].
*/
if (period > 0xffff) {
pwmc0 = ilog2(period >> 16);
if (WARN_ON(pwmc0 > 3))
return -EINVAL;
} else {
pwmc0 = 0;
}
pwmc0 = fls(period >> 16);
if (WARN_ON(pwmc0 > 3))
return -EINVAL;
period >>= pwmc0;
duty_cycle >>= pwmc0;