Commit 50cc7e3e authored Oct 14, 2019 by Ondrej Jirman Committed by Thierry Reding Oct 21, 2019

pwm: sun4i: Fix incorrect calculation of duty_cycle/period



Since 5.4-rc1, pwm_apply_state calls ->get_state after ->apply
if available, and this revealed an issue with integer precision
when calculating duty_cycle and period for the currently set
state in ->get_state callback.

This issue manifested in broken backlight on several Allwinner
based devices.

Previously this worked, because ->apply updated the passed state
directly.

Fixes: deb9c462 ("pwm: sun4i: Don't update the state for the caller of pwm_apply_state")
Signed-off-by: Ondrej Jirman <megous@megous.com>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

parent 2d3aa06b

drivers/pwm/pwm-sun4i.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -137,10 +137,10 @@ static void sun4i_pwm_get_state(struct pwm_chip *chip,

		val = sun4i_pwm_readl(sun4i_pwm, PWM_CH_PRD(pwm->hwpwm));

		tmp = prescaler * NSEC_PER_SEC * PWM_REG_DTY(val);
		tmp = (u64)prescaler * NSEC_PER_SEC * PWM_REG_DTY(val);
		state->duty_cycle = DIV_ROUND_CLOSEST_ULL(tmp, clk_rate);

		tmp = prescaler * NSEC_PER_SEC * PWM_REG_PRD(val);
		tmp = (u64)prescaler * NSEC_PER_SEC * PWM_REG_PRD(val);
		state->period = DIV_ROUND_CLOSEST_ULL(tmp, clk_rate);
		}

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