Commit aef1a379 authored by Uwe Kleine-König's avatar Uwe Kleine-König Committed by Thierry Reding
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pwm: imx27: Fix rounding behavior 



To not trigger the warnings provided by CONFIG_PWM_DEBUG

 - use up-rounding in .get_state()
 - don't divide by the result of a division
 - don't use the rounded counter value for the period length to calculate
   the counter value for the duty cycle

Signed-off-by: default avatarUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: default avatarThierry Reding <thierry.reding@gmail.com>
parent cad0f296

drivers/pwm/pwm-imx27.c

+10 −10
Original line number Diff line number Diff line
@@ -150,13 +150,12 @@ static void pwm_imx27_get_state(struct pwm_chip *chip, 


	prescaler = MX3_PWMCR_PRESCALER_GET(val);

	pwm_clk = clk_get_rate(imx->clk_per);

	pwm_clk = DIV_ROUND_CLOSEST_ULL(pwm_clk, prescaler);

	val = readl(imx->mmio_base + MX3_PWMPR);

	period = val >= MX3_PWMPR_MAX ? MX3_PWMPR_MAX : val;



	/* PWMOUT (Hz) = PWMCLK / (PWMPR + 2) */

	tmp = NSEC_PER_SEC * (u64)(period + 2);

	state->period = DIV_ROUND_CLOSEST_ULL(tmp, pwm_clk);

	tmp = NSEC_PER_SEC * (u64)(period + 2) * prescaler;

	state->period = DIV_ROUND_UP_ULL(tmp, pwm_clk);



	/*

	 * PWMSAR can be read only if PWM is enabled. If the PWM is disabled,
@@ -167,8 +166,8 @@ static void pwm_imx27_get_state(struct pwm_chip *chip, 
	else

		val = imx->duty_cycle;



	tmp = NSEC_PER_SEC * (u64)(val);

	state->duty_cycle = DIV_ROUND_CLOSEST_ULL(tmp, pwm_clk);

	tmp = NSEC_PER_SEC * (u64)(val) * prescaler;

	state->duty_cycle = DIV_ROUND_UP_ULL(tmp, pwm_clk);



	pwm_imx27_clk_disable_unprepare(imx);

}
@@ -220,22 +219,23 @@ static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm, 
	struct pwm_imx27_chip *imx = to_pwm_imx27_chip(chip);

	struct pwm_state cstate;

	unsigned long long c;

	unsigned long long clkrate;

	int ret;

	u32 cr;



	pwm_get_state(pwm, &cstate);



	c = clk_get_rate(imx->clk_per);

	c *= state->period;

	clkrate = clk_get_rate(imx->clk_per);

	c = clkrate * state->period;



	do_div(c, 1000000000);

	do_div(c, NSEC_PER_SEC);

	period_cycles = c;



	prescale = period_cycles / 0x10000 + 1;



	period_cycles /= prescale;

	c = (unsigned long long)period_cycles * state->duty_cycle;

	do_div(c, state->period);

	c = clkrate * state->duty_cycle;

	do_div(c, NSEC_PER_SEC * prescale);

	duty_cycles = c;



	/*

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