From: Marco Felsch <m.felsch@pengutronix.de> To: thierry.reding@gmail.com, u.kleine-koenig@pengutronix.de, lee.jones@linaro.org, shawnguo@kernel.org, s.hauer@pengutronix.de, festevam@gmail.com, linux-imx@nxp.com, Anson.Huang@nxp.com, michal.vokac@ysoft.com, l.majewski@majess.pl Cc: linux-pwm@vger.kernel.org, kernel@pengutronix.de, linux-arm-kernel@lists.infradead.org Subject: [PATCH v2 5/5] pwm: imx27: wait till the duty cycle is applied Date: Fri, 25 Sep 2020 17:53:30 +0200 [thread overview] Message-ID: <20200925155330.32301-6-m.felsch@pengutronix.de> (raw) In-Reply-To: <20200925155330.32301-1-m.felsch@pengutronix.de> Currently the driver don't check if the new state was applied or not. This can cause glitches on the output pin if the new state disables the PWM. In this case the PWM clocks are disabled before the new duty cycle value gets applied. The fix is to wait till the desired duty cycle was applied. Signed-off-by: Marco Felsch <m.felsch@pengutronix.de> --- v2: - new patch drivers/pwm/pwm-imx27.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/drivers/pwm/pwm-imx27.c b/drivers/pwm/pwm-imx27.c index 07c6a263a39c..ffa00bcd81da 100644 --- a/drivers/pwm/pwm-imx27.c +++ b/drivers/pwm/pwm-imx27.c @@ -222,6 +222,26 @@ static int pwm_imx27_get_fifo_slot(struct pwm_chip *chip, return fifoav; } +static int pwm_imx27_wait_till_applied(struct pwm_chip *chip, + struct pwm_device *pwm) +{ + unsigned int attempts = 4; + unsigned int period_ms; + int busy_slots; + + do { + busy_slots = pwm_imx27_get_fifo_slot(chip, pwm); + if (busy_slots == 0) + return 0; + + period_ms = DIV_ROUND_UP(pwm_get_period(pwm), + NSEC_PER_MSEC); + msleep(period_ms); + } while (attempts--); + + return -ETIMEDOUT; +} + static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm, const struct pwm_state *state) { @@ -277,6 +297,11 @@ static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm, writel(duty_cycles, imx->mmio_base + MX3_PWMSAR); else writel(0, imx->mmio_base + MX3_PWMSAR); + + ret = pwm_imx27_wait_till_applied(chip, pwm); + if (ret) + goto out; + writel(period_cycles, imx->mmio_base + MX3_PWMPR); /* -- 2.20.1
WARNING: multiple messages have this Message-ID (diff)
From: Marco Felsch <m.felsch@pengutronix.de> To: thierry.reding@gmail.com, u.kleine-koenig@pengutronix.de, lee.jones@linaro.org, shawnguo@kernel.org, s.hauer@pengutronix.de, festevam@gmail.com, linux-imx@nxp.com, Anson.Huang@nxp.com, michal.vokac@ysoft.com, l.majewski@majess.pl Cc: linux-pwm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kernel@pengutronix.de Subject: [PATCH v2 5/5] pwm: imx27: wait till the duty cycle is applied Date: Fri, 25 Sep 2020 17:53:30 +0200 [thread overview] Message-ID: <20200925155330.32301-6-m.felsch@pengutronix.de> (raw) In-Reply-To: <20200925155330.32301-1-m.felsch@pengutronix.de> Currently the driver don't check if the new state was applied or not. This can cause glitches on the output pin if the new state disables the PWM. In this case the PWM clocks are disabled before the new duty cycle value gets applied. The fix is to wait till the desired duty cycle was applied. Signed-off-by: Marco Felsch <m.felsch@pengutronix.de> --- v2: - new patch drivers/pwm/pwm-imx27.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/drivers/pwm/pwm-imx27.c b/drivers/pwm/pwm-imx27.c index 07c6a263a39c..ffa00bcd81da 100644 --- a/drivers/pwm/pwm-imx27.c +++ b/drivers/pwm/pwm-imx27.c @@ -222,6 +222,26 @@ static int pwm_imx27_get_fifo_slot(struct pwm_chip *chip, return fifoav; } +static int pwm_imx27_wait_till_applied(struct pwm_chip *chip, + struct pwm_device *pwm) +{ + unsigned int attempts = 4; + unsigned int period_ms; + int busy_slots; + + do { + busy_slots = pwm_imx27_get_fifo_slot(chip, pwm); + if (busy_slots == 0) + return 0; + + period_ms = DIV_ROUND_UP(pwm_get_period(pwm), + NSEC_PER_MSEC); + msleep(period_ms); + } while (attempts--); + + return -ETIMEDOUT; +} + static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm, const struct pwm_state *state) { @@ -277,6 +297,11 @@ static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm, writel(duty_cycles, imx->mmio_base + MX3_PWMSAR); else writel(0, imx->mmio_base + MX3_PWMSAR); + + ret = pwm_imx27_wait_till_applied(chip, pwm); + if (ret) + goto out; + writel(period_cycles, imx->mmio_base + MX3_PWMPR); /* -- 2.20.1 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2020-09-25 15:53 UTC|newest] Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-09-25 15:53 [PATCH v2 0/5] PWM i.MX27 fix disabled state for inverted signals Marco Felsch 2020-09-25 15:53 ` Marco Felsch 2020-09-25 15:53 ` [PATCH v2 1/5] pwm: imx27: enable clock unconditional for register access Marco Felsch 2020-09-25 15:53 ` Marco Felsch 2020-09-26 13:28 ` Uwe Kleine-König 2020-09-26 13:28 ` Uwe Kleine-König 2020-09-26 13:48 ` Uwe Kleine-König 2020-09-26 13:48 ` Uwe Kleine-König 2020-09-28 5:52 ` Marco Felsch 2020-09-28 5:52 ` Marco Felsch 2020-09-25 15:53 ` [PATCH v2 2/5] pwm: imx27: move constant PWMCR register values into probe Marco Felsch 2020-09-25 15:53 ` Marco Felsch 2020-09-26 13:46 ` Uwe Kleine-König 2020-09-26 13:46 ` Uwe Kleine-König 2020-09-28 5:50 ` Marco Felsch 2020-09-28 5:50 ` Marco Felsch 2020-09-25 15:53 ` [PATCH v2 3/5] pwm: imx27: reset the PWM if it is not running Marco Felsch 2020-09-25 15:53 ` Marco Felsch 2020-09-28 7:30 ` Uwe Kleine-König 2020-09-28 7:30 ` Uwe Kleine-König 2020-09-28 9:29 ` Marco Felsch 2020-09-28 9:29 ` Marco Felsch 2020-09-25 15:53 ` [PATCH v2 4/5] pwm: imx27: fix disable state for inverted PWMs Marco Felsch 2020-09-25 15:53 ` Marco Felsch 2020-09-28 7:47 ` Uwe Kleine-König 2020-09-28 7:47 ` Uwe Kleine-König 2020-09-28 9:52 ` Marco Felsch 2020-09-28 9:52 ` Marco Felsch 2020-09-28 19:06 ` Uwe Kleine-König 2020-09-28 19:06 ` Uwe Kleine-König 2020-09-29 5:23 ` Marco Felsch 2020-09-29 5:23 ` Marco Felsch 2020-09-25 15:53 ` Marco Felsch [this message] 2020-09-25 15:53 ` [PATCH v2 5/5] pwm: imx27: wait till the duty cycle is applied Marco Felsch 2020-09-28 8:04 ` Uwe Kleine-König 2020-09-28 8:04 ` Uwe Kleine-König 2020-09-28 9:59 ` Marco Felsch 2020-09-28 9:59 ` Marco Felsch
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