Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit b4f9a726 authored by Yoshihiro Shimoda's avatar Yoshihiro Shimoda Committed by Thierry Reding
Browse files

pwm: rcar: Improve calculation of divider 



The rcar_pwm_get_clock_division() has a loop to calculate the divider,
but the value of div should be calculatable without a loop. So, this
patch improves it.

This algorithm is suggested by Uwe Kleine-König and Laurent Pinchart.

Signed-off-by: default avatarYoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Acked-by: default avatarUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: default avatarThierry Reding <thierry.reding@gmail.com>
parent 8cc2b970

drivers/pwm/pwm-rcar.c

+7 −9
Original line number Diff line number Diff line
@@ -8,6 +8,8 @@ 
#include <linux/clk.h>

#include <linux/err.h>

#include <linux/io.h>

#include <linux/log2.h>

#include <linux/math64.h>

#include <linux/module.h>

#include <linux/of.h>

#include <linux/platform_device.h>
@@ -68,19 +70,15 @@ static void rcar_pwm_update(struct rcar_pwm_chip *rp, u32 mask, u32 data, 
static int rcar_pwm_get_clock_division(struct rcar_pwm_chip *rp, int period_ns)

{

	unsigned long clk_rate = clk_get_rate(rp->clk);

	unsigned long long max; /* max cycle / nanoseconds */

	unsigned int div;

	u64 div, tmp;



	if (clk_rate == 0)

		return -EINVAL;



	for (div = 0; div <= RCAR_PWM_MAX_DIVISION; div++) {

		max = (unsigned long long)NSEC_PER_SEC * RCAR_PWM_MAX_CYCLE *

			(1 << div);

		do_div(max, clk_rate);

		if (period_ns <= max)

			break;

	}

	div = (u64)NSEC_PER_SEC * RCAR_PWM_MAX_CYCLE;

	tmp = (u64)period_ns * clk_rate + div - 1;

	tmp = div64_u64(tmp, div);

	div = ilog2(tmp - 1) + 1;



	return (div <= RCAR_PWM_MAX_DIVISION) ? div : -ERANGE;

}