Commit 937efa29 authored by Uwe Kleine-König's avatar Uwe Kleine-König Committed by Thierry Reding
Browse files

pwm: visconti: Fix and simplify period calculation 



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: 721b5957 ("pwm: visconti: Add Toshiba Visconti SoC PWM support")
Signed-off-by: default avatarUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: default avatarNobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp>
Signed-off-by: default avatarThierry Reding <thierry.reding@gmail.com>
parent e9fdf122

drivers/pwm/pwm-visconti.c

+7 −10
Original line number Diff line number Diff line
@@ -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);

	pwmc0 = fls(period >> 16);

	if (WARN_ON(pwmc0 > 3))

		return -EINVAL;

	} else {

		pwmc0 = 0;

	}



	period >>= pwmc0;

	duty_cycle >>= pwmc0;