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From: Roman Beranek <roman.beranek@prusa3d.cz>
To: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
Cc: Thierry Reding <thierry.reding@gmail.com>,
	Emil Lenngren <emil.lenngren@gmail.com>,
	Pascal Roeleven <dev@pascalroeleven.nl>,
	Lee Jones <lee.jones@linaro.org>,
	Maxime Ripard <mripard@kernel.org>, Chen-Yu Tsai <wens@csie.org>,
	linux-pwm@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-sunxi@lists.linux.dev, linux-sunxi@googlegroups.com
Subject: [PATCH 3/6] pwm: sun4i: replace spinlock with a mutex
Date: Mon, 31 May 2021 06:46:05 +0200	[thread overview]
Message-ID: <20210531044608.1006024-4-roman.beranek@prusa3d.com> (raw)
In-Reply-To: <20210531044608.1006024-1-roman.beranek@prusa3d.com>

Releasing ctrl_lock for the duration of the delay is not desirable as it
allows re-enabling the PWM before the delay is over. Instead, substitute
the spinlock with a mutex so that we can sleep while holding it.

Signed-off-by: Roman Beranek <roman.beranek@prusa3d.com>
---
 drivers/pwm/pwm-sun4i.c | 20 +++++++++-----------
 1 file changed, 9 insertions(+), 11 deletions(-)

diff --git a/drivers/pwm/pwm-sun4i.c b/drivers/pwm/pwm-sun4i.c
index 2777abe66f79..b3ec59a83d00 100644
--- a/drivers/pwm/pwm-sun4i.c
+++ b/drivers/pwm/pwm-sun4i.c
@@ -16,13 +16,13 @@
 #include <linux/io.h>
 #include <linux/jiffies.h>
 #include <linux/module.h>
+#include <linux/mutex.h>
 #include <linux/of.h>
 #include <linux/of_device.h>
 #include <linux/platform_device.h>
 #include <linux/pwm.h>
 #include <linux/reset.h>
 #include <linux/slab.h>
-#include <linux/spinlock.h>
 #include <linux/time.h>
 
 #define PWM_CTRL_REG		0x0
@@ -87,7 +87,7 @@ struct sun4i_pwm_chip {
 	struct clk *clk;
 	struct reset_control *rst;
 	void __iomem *base;
-	spinlock_t ctrl_lock;
+	struct mutex ctrl_lock;
 	const struct sun4i_pwm_data *data;
 	unsigned long next_period[2];
 };
@@ -265,7 +265,7 @@ static int sun4i_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 		return ret;
 	}
 
-	spin_lock(&sun4i_pwm->ctrl_lock);
+	mutex_lock(&sun4i_pwm->ctrl_lock);
 	ctrl = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG);
 
 	if (sun4i_pwm->data->has_direct_mod_clk_output) {
@@ -273,7 +273,7 @@ static int sun4i_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 			ctrl |= BIT_CH(PWM_BYPASS, pwm->hwpwm);
 			/* We can skip other parameter */
 			sun4i_pwm_writel(sun4i_pwm, ctrl, PWM_CTRL_REG);
-			spin_unlock(&sun4i_pwm->ctrl_lock);
+			mutex_unlock(&sun4i_pwm->ctrl_lock);
 			return 0;
 		}
 
@@ -308,10 +308,10 @@ static int sun4i_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 
 	sun4i_pwm_writel(sun4i_pwm, ctrl, PWM_CTRL_REG);
 
-	spin_unlock(&sun4i_pwm->ctrl_lock);
-
-	if (state->enabled)
+	if (state->enabled) {
+		mutex_unlock(&sun4i_pwm->ctrl_lock);
 		return 0;
+	}
 
 	/* We need a full period to elapse before disabling the channel. */
 	now = jiffies;
@@ -324,11 +324,9 @@ static int sun4i_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 			usleep_range(delay_us, delay_us * 2);
 	}
 
-	spin_lock(&sun4i_pwm->ctrl_lock);
-	ctrl = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG);
 	ctrl &= ~BIT_CH(PWM_CLK_GATING, pwm->hwpwm);
 	sun4i_pwm_writel(sun4i_pwm, ctrl, PWM_CTRL_REG);
-	spin_unlock(&sun4i_pwm->ctrl_lock);
+	mutex_unlock(&sun4i_pwm->ctrl_lock);
 
 	clk_disable_unprepare(sun4i_pwm->clk);
 
@@ -471,7 +469,7 @@ static int sun4i_pwm_probe(struct platform_device *pdev)
 	pwm->chip.of_xlate = of_pwm_xlate_with_flags;
 	pwm->chip.of_pwm_n_cells = 3;
 
-	spin_lock_init(&pwm->ctrl_lock);
+	mutex_init(&pwm->ctrl_lock);
 
 	ret = pwmchip_add(&pwm->chip);
 	if (ret < 0) {
-- 
2.31.1


  parent reply	other threads:[~2021-05-31  4:46 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-31  4:46 [PATCH 0/6] pwm: sun4i: only wait 2 cycles prior to disabling Roman Beranek
2021-05-31  4:46 ` [PATCH 1/6] pwm: sun4i: enable clk prior to getting its rate Roman Beranek
2021-06-07  8:00   ` Uwe Kleine-König
2021-05-31  4:46 ` [PATCH 2/6] pwm: sun4i: disable EN bit prior to the delay Roman Beranek
2021-06-07  8:07   ` Uwe Kleine-König
2021-05-31  4:46 ` Roman Beranek [this message]
2021-05-31  4:46 ` [PATCH 4/6] pwm: sun4i: simplify calculation of the delay time Roman Beranek
2021-05-31  4:46 ` [PATCH 5/6] pwm: sun4i: shorten the delay to 2 cycles Roman Beranek
2021-05-31  4:46 ` [PATCH 6/6] pwm: sun4i: don't delay if the PWM is already off Roman Beranek
2021-06-10 13:41   ` Pascal Roeleven
2021-05-31 19:07 ` [PATCH 0/6] pwm: sun4i: only wait 2 cycles prior to disabling Pascal Roeleven
2021-05-31 20:01   ` Emil Lenngren
2021-05-31 20:20     ` Pascal Roeleven
2021-06-08 12:28   ` Pascal Roeleven

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