From: Baruch Siach <baruch@tkos.co.il>
To: "Thierry Reding" <thierry.reding@gmail.com>,
"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
"Lee Jones" <lee.jones@linaro.org>,
"Linus Walleij" <linus.walleij@linaro.org>,
"Bartosz Golaszewski" <bgolaszewski@baylibre.com>
Cc: Baruch Siach <baruch@tkos.co.il>, Andrew Lunn <andrew@lunn.ch>,
Gregory Clement <gregory.clement@bootlin.com>,
Russell King <linux@armlinux.org.uk>,
Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>,
Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
Chris Packham <chris.packham@alliedtelesis.co.nz>,
Sascha Hauer <s.hauer@pengutronix.de>,
Ralph Sennhauser <ralph.sennhauser@gmail.com>,
linux-pwm@vger.kernel.org, linux-gpio@vger.kernel.org,
linux-arm-kernel@lists.infradead.org
Subject: [PATCH v4 2/5] gpio: mvebu: improve pwm period calculation accuracy
Date: Sun, 17 Jan 2021 15:17:03 +0200 [thread overview]
Message-ID: <a56e1e2a0ed2e9ce1ef7c9b336ab1b7c5efd2802.1610882271.git.baruch@tkos.co.il> (raw)
In-Reply-To: <cover.1610882271.git.baruch@tkos.co.il>
Change 'off' register value calculation from
$off = (period - duty_cycle) * clkrate / NSEC_PER_SEC
to
$off = (period * clkrate / NSEC_PER_SEC) - $on
That is, divide the full period value to reduce rounding error.
Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
---
drivers/gpio/gpio-mvebu.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/gpio/gpio-mvebu.c b/drivers/gpio/gpio-mvebu.c
index a912a8fed197..c424d88e9e2b 100644
--- a/drivers/gpio/gpio-mvebu.c
+++ b/drivers/gpio/gpio-mvebu.c
@@ -715,9 +715,9 @@ static int mvebu_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
else
on = 1;
- val = (unsigned long long) mvpwm->clk_rate *
- (state->period - state->duty_cycle);
+ val = (unsigned long long) mvpwm->clk_rate * state->period;
do_div(val, NSEC_PER_SEC);
+ val -= on;
if (val > UINT_MAX)
return -EINVAL;
if (val)
--
2.29.2
next prev parent reply other threads:[~2021-01-17 13:18 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-17 13:17 [PATCH v4 0/5] gpio: mvebu: pwm fixes and improvements Baruch Siach
2021-01-17 13:17 ` [PATCH v4 1/5] gpio: mvebu: fix pwm .get_state period calculation Baruch Siach
2021-01-19 11:00 ` Bartosz Golaszewski
2021-01-17 13:17 ` Baruch Siach [this message]
2021-01-17 13:17 ` [PATCH v4 3/5] gpio: mvebu: make pwm .get_state closer to idempotent Baruch Siach
2021-01-17 13:17 ` [PATCH v4 4/5] gpio: mvebu: don't limit pwm period/duty_cycle to UINT_MAX Baruch Siach
2021-01-17 13:17 ` [PATCH v4 5/5] gpio: mvebu: improve handling of pwm zero on/off values Baruch Siach
2021-01-19 19:39 ` Uwe Kleine-König
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