From: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
To: thierry.reding@gmail.com
Cc: linux-pwm@vger.kernel.org, linux-renesas-soc@vger.kernel.org,
Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Subject: [PATCH v3 4/4] pwm: rcar: improve calculation of divider
Date: Wed, 9 Jan 2019 17:19:08 +0900 [thread overview]
Message-ID: <1547021948-7664-5-git-send-email-yoshihiro.shimoda.uh@renesas.com> (raw)
In-Reply-To: <1547021948-7664-1-git-send-email-yoshihiro.shimoda.uh@renesas.com>
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: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
---
drivers/pwm/pwm-rcar.c | 16 +++++++---------
1 file changed, 7 insertions(+), 9 deletions(-)
diff --git a/drivers/pwm/pwm-rcar.c b/drivers/pwm/pwm-rcar.c
index 1e13fbb..cfe7dd1 100644
--- a/drivers/pwm/pwm-rcar.c
+++ b/drivers/pwm/pwm-rcar.c
@@ -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;
}
--
1.9.1
next prev parent reply other threads:[~2019-01-09 8:22 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-09 8:19 [PATCH v3 0/4] pwm: rcar: Add support "atomic" API and improve calculation Yoshihiro Shimoda
2019-01-09 8:19 ` [PATCH v3 1/4] pwm: rcar: Add support "atomic" API Yoshihiro Shimoda
2019-01-09 8:19 ` [PATCH v3 2/4] pwm: rcar: Use "atomic" API on rcar_pwm_resume() Yoshihiro Shimoda
2019-03-04 11:18 ` Thierry Reding
2019-01-09 8:19 ` [PATCH v3 3/4] pwm: rcar: remove legacy APIs Yoshihiro Shimoda
2019-01-09 8:19 ` Yoshihiro Shimoda [this message]
2019-03-04 11:14 ` [PATCH v3 0/4] pwm: rcar: Add support "atomic" API and improve calculation Thierry Reding
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