Merge tag 'pwm/for-5.6-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/thierry.reding/linux-pwm

Pull pwm updates from Thierry Reding:
 "Mostly cleanups and minor improvements with some new chip support for
  some drivers"

* tag 'pwm/for-5.6-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/thierry.reding/linux-pwm: (37 commits)
  pwm: Remove set but not set variable 'pwm'
  pwm: sun4i: Initialize variables before use
  pwm: stm32: Remove automatic output enable
  pwm: sun4i: Narrow scope of local variable
  pwm: bcm2835: Allow building for ARCH_BRCMSTB
  pwm: imx27: Eliminate error message for defer probe
  pwm: sun4i: Fix inconsistent IS_ERR and PTR_ERR
  pwm: sun4i: Move pwm_calculate() out of spin_lock()
  pwm: omap-dmtimer: Allow compiling with COMPILE_TEST
  pwm: omap-dmtimer: put_device() after of_find_device_by_node()
  pwm: omap-dmtimer: Simplify error handling
  pwm: omap-dmtimer: Remove PWM chip in .remove before making it unfunctional
  pwm: Implement tracing for .get_state() and .apply_state()
  pwm: rcar: Document inability to set duty_cycle = 0
  pwm: rcar: Drop useless call to pwm_get_state()
  pwm: Fix minor Kconfig whitespace issues
  pwm: atmel: Implement .get_state()
  pwm: atmel: Use register accessors for channels
  pwm: atmel: Document known weaknesses of both hardware and software
  pwm: atmel: Replace loop in prescale calculation by ad-hoc calculation
  ...

11 files changed, 479 insertions, 197 deletions

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index bd21655c37a6..30190beeb6e9 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -100,7 +100,7 @@ config PWM_BCM_KONA
 
 config PWM_BCM2835
 	tristate "BCM2835 PWM support"
-	depends on ARCH_BCM2835
+	depends on ARCH_BCM2835 || ARCH_BRCMSTB
 	help
 	  PWM framework driver for BCM2835 controller (Raspberry Pi)
 
@@ -328,7 +328,8 @@ config PWM_MXS
 
 config PWM_OMAP_DMTIMER
 	tristate "OMAP Dual-Mode Timer PWM support"
-	depends on OF && ARCH_OMAP && OMAP_DM_TIMER
+	depends on OF
+	depends on OMAP_DM_TIMER || COMPILE_TEST
 	help
 	  Generic PWM framework driver for OMAP Dual-Mode Timer PWM output
 
@@ -490,7 +491,7 @@ config PWM_TEGRA
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-tegra.
 
-config  PWM_TIECAP
+config PWM_TIECAP
 	tristate "ECAP PWM support"
 	depends on ARCH_OMAP2PLUS || ARCH_DAVINCI_DA8XX || ARCH_KEYSTONE || ARCH_K3
 	help
@@ -499,7 +500,7 @@ config  PWM_TIECAP
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-tiecap.
 
-config  PWM_TIEHRPWM
+config PWM_TIEHRPWM
 	tristate "EHRPWM PWM support"
 	depends on ARCH_OMAP2PLUS || ARCH_DAVINCI_DA8XX || ARCH_K3
 	help
diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index f877e77d9184..5a7f6598c05f 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -20,6 +20,9 @@
 
 #include <dt-bindings/pwm/pwm.h>
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/pwm.h>
+
 #define MAX_PWMS 1024
 
 static DEFINE_MUTEX(pwm_lookup_lock);
@@ -114,6 +117,11 @@ static int pwm_device_request(struct pwm_device *pwm, const char *label)
 		}
 	}
 
+	if (pwm->chip->ops->get_state) {
+		pwm->chip->ops->get_state(pwm->chip, pwm, &pwm->state);
+		trace_pwm_get(pwm, &pwm->state);
+	}
+
 	set_bit(PWMF_REQUESTED, &pwm->flags);
 	pwm->label = label;
 
@@ -283,9 +291,6 @@ int pwmchip_add_with_polarity(struct pwm_chip *chip,
 		pwm->hwpwm = i;
 		pwm->state.polarity = polarity;
 
-		if (chip->ops->get_state)
-			chip->ops->get_state(chip, pwm, &pwm->state);
-
 		radix_tree_insert(&pwm_tree, pwm->pwm, pwm);
 	}
 
@@ -472,6 +477,8 @@ int pwm_apply_state(struct pwm_device *pwm, const struct pwm_state *state)
 		if (err)
 			return err;
 
+		trace_pwm_apply(pwm, state);
+
 		pwm->state = *state;
 	} else {
 		/*
diff --git a/drivers/pwm/pwm-atmel.c b/drivers/pwm/pwm-atmel.c
index 9ba733467e26..6161e7e3e9ac 100644
--- a/drivers/pwm/pwm-atmel.c
+++ b/drivers/pwm/pwm-atmel.c
@@ -4,6 +4,19 @@
  *
  * Copyright (C) 2013 Atmel Corporation
  *		 Bo Shen <voice.shen@atmel.com>
+ *
+ * Links to reference manuals for the supported PWM chips can be found in
+ * Documentation/arm/microchip.rst.
+ *
+ * Limitations:
+ * - Periods start with the inactive level.
+ * - Hardware has to be stopped in general to update settings.
+ *
+ * Software bugs/possible improvements:
+ * - When atmel_pwm_apply() is called with state->enabled=false a change in
+ *   state->polarity isn't honored.
+ * - Instead of sleeping to wait for a completed period, the interrupt
+ *   functionality could be used.
  */
 
 #include <linux/clk.h>
@@ -47,6 +60,8 @@
 #define PWMV2_CPRD		0x0C
 #define PWMV2_CPRDUPD		0x10
 
+#define PWM_MAX_PRES		10
+
 struct atmel_pwm_registers {
 	u8 period;
 	u8 period_upd;
@@ -55,8 +70,7 @@ struct atmel_pwm_registers {
 };
 
 struct atmel_pwm_config {
-	u32 max_period;
-	u32 max_pres;
+	u32 period_bits;
 };
 
 struct atmel_pwm_data {
@@ -97,7 +111,7 @@ static inline u32 atmel_pwm_ch_readl(struct atmel_pwm_chip *chip,
 {
 	unsigned long base = PWM_CH_REG_OFFSET + ch * PWM_CH_REG_SIZE;
 
-	return readl_relaxed(chip->base + base + offset);
+	return atmel_pwm_readl(chip, base + offset);
 }
 
 static inline void atmel_pwm_ch_writel(struct atmel_pwm_chip *chip,
@@ -106,7 +120,7 @@ static inline void atmel_pwm_ch_writel(struct atmel_pwm_chip *chip,
 {
 	unsigned long base = PWM_CH_REG_OFFSET + ch * PWM_CH_REG_SIZE;
 
-	writel_relaxed(val, chip->base + base + offset);
+	atmel_pwm_writel(chip, base + offset, val);
 }
 
 static int atmel_pwm_calculate_cprd_and_pres(struct pwm_chip *chip,
@@ -115,17 +129,27 @@ static int atmel_pwm_calculate_cprd_and_pres(struct pwm_chip *chip,
 {
 	struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
 	unsigned long long cycles = state->period;
+	int shift;
 
 	/* Calculate the period cycles and prescale value */
 	cycles *= clk_get_rate(atmel_pwm->clk);
 	do_div(cycles, NSEC_PER_SEC);
 
-	for (*pres = 0; cycles > atmel_pwm->data->cfg.max_period; cycles >>= 1)
-		(*pres)++;
+	/*
+	 * The register for the period length is cfg.period_bits bits wide.
+	 * So for each bit the number of clock cycles is wider divide the input
+	 * clock frequency by two using pres and shift cprd accordingly.
+	 */
+	shift = fls(cycles) - atmel_pwm->data->cfg.period_bits;
 
-	if (*pres > atmel_pwm->data->cfg.max_pres) {
+	if (shift > PWM_MAX_PRES) {
 		dev_err(chip->dev, "pres exceeds the maximum value\n");
 		return -EINVAL;
+	} else if (shift > 0) {
+		*pres = shift;
+		cycles >>= *pres;
+	} else {
+		*pres = 0;
 	}
 
 	*cprd = cycles;
@@ -271,8 +295,48 @@ static int atmel_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	return 0;
 }
 
+static void atmel_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
+				struct pwm_state *state)
+{
+	struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
+	u32 sr, cmr;
+
+	sr = atmel_pwm_readl(atmel_pwm, PWM_SR);
+	cmr = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm, PWM_CMR);
+
+	if (sr & (1 << pwm->hwpwm)) {
+		unsigned long rate = clk_get_rate(atmel_pwm->clk);
+		u32 cdty, cprd, pres;
+		u64 tmp;
+
+		pres = cmr & PWM_CMR_CPRE_MSK;
+
+		cprd = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm,
+					  atmel_pwm->data->regs.period);
+		tmp = (u64)cprd * NSEC_PER_SEC;
+		tmp <<= pres;
+		state->period = DIV64_U64_ROUND_UP(tmp, rate);
+
+		cdty = atmel_pwm_ch_readl(atmel_pwm, pwm->hwpwm,
+					  atmel_pwm->data->regs.duty);
+		tmp = (u64)cdty * NSEC_PER_SEC;
+		tmp <<= pres;
+		state->duty_cycle = DIV64_U64_ROUND_UP(tmp, rate);
+
+		state->enabled = true;
+	} else {
+		state->enabled = false;
+	}
+
+	if (cmr & PWM_CMR_CPOL)
+		state->polarity = PWM_POLARITY_INVERSED;
+	else
+		state->polarity = PWM_POLARITY_NORMAL;
+}
+
 static const struct pwm_ops atmel_pwm_ops = {
 	.apply = atmel_pwm_apply,
+	.get_state = atmel_pwm_get_state,
 	.owner = THIS_MODULE,
 };
 
@@ -285,8 +349,7 @@ static const struct atmel_pwm_data atmel_sam9rl_pwm_data = {
 	},
 	.cfg = {
 		/* 16 bits to keep period and duty. */
-		.max_period	= 0xffff,
-		.max_pres	= 10,
+		.period_bits	= 16,
 	},
 };
 
@@ -299,8 +362,7 @@ static const struct atmel_pwm_data atmel_sama5_pwm_data = {
 	},
 	.cfg = {
 		/* 16 bits to keep period and duty. */
-		.max_period	= 0xffff,
-		.max_pres	= 10,
+		.period_bits	= 16,
 	},
 };
 
@@ -313,8 +375,7 @@ static const struct atmel_pwm_data mchp_sam9x60_pwm_data = {
 	},
 	.cfg = {
 		/* 32 bits to keep period and duty. */
-		.max_period	= 0xffffffff,
-		.max_pres	= 10,
+		.period_bits	= 32,
 	},
 };
 
diff --git a/drivers/pwm/pwm-cros-ec.c b/drivers/pwm/pwm-cros-ec.c
index 89497448d217..09c08dee099e 100644
--- a/drivers/pwm/pwm-cros-ec.c
+++ b/drivers/pwm/pwm-cros-ec.c
@@ -25,11 +25,39 @@ struct cros_ec_pwm_device {
 	struct pwm_chip chip;
 };
 
+/**
+ * struct cros_ec_pwm - per-PWM driver data
+ * @duty_cycle: cached duty cycle
+ */
+struct cros_ec_pwm {
+	u16 duty_cycle;
+};
+
 static inline struct cros_ec_pwm_device *pwm_to_cros_ec_pwm(struct pwm_chip *c)
 {
 	return container_of(c, struct cros_ec_pwm_device, chip);
 }
 
+static int cros_ec_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	struct cros_ec_pwm *channel;
+
+	channel = kzalloc(sizeof(*channel), GFP_KERNEL);
+	if (!channel)
+		return -ENOMEM;
+
+	pwm_set_chip_data(pwm, channel);
+
+	return 0;
+}
+
+static void cros_ec_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	struct cros_ec_pwm *channel = pwm_get_chip_data(pwm);
+
+	kfree(channel);
+}
+
 static int cros_ec_pwm_set_duty(struct cros_ec_device *ec, u8 index, u16 duty)
 {
 	struct {
@@ -96,7 +124,9 @@ static int cros_ec_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 			     const struct pwm_state *state)
 {
 	struct cros_ec_pwm_device *ec_pwm = pwm_to_cros_ec_pwm(chip);
-	int duty_cycle;
+	struct cros_ec_pwm *channel = pwm_get_chip_data(pwm);
+	u16 duty_cycle;
+	int ret;
 
 	/* The EC won't let us change the period */
 	if (state->period != EC_PWM_MAX_DUTY)
@@ -108,13 +138,20 @@ static int cros_ec_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	 */
 	duty_cycle = state->enabled ? state->duty_cycle : 0;
 
-	return cros_ec_pwm_set_duty(ec_pwm->ec, pwm->hwpwm, duty_cycle);
+	ret = cros_ec_pwm_set_duty(ec_pwm->ec, pwm->hwpwm, duty_cycle);
+	if (ret < 0)
+		return ret;
+
+	channel->duty_cycle = state->duty_cycle;
+
+	return 0;
 }
 
 static void cros_ec_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
 				  struct pwm_state *state)
 {
 	struct cros_ec_pwm_device *ec_pwm = pwm_to_cros_ec_pwm(chip);
+	struct cros_ec_pwm *channel = pwm_get_chip_data(pwm);
 	int ret;
 
 	ret = cros_ec_pwm_get_duty(ec_pwm->ec, pwm->hwpwm);
@@ -126,8 +163,19 @@ static void cros_ec_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
 	state->enabled = (ret > 0);
 	state->period = EC_PWM_MAX_DUTY;
 
-	/* Note that "disabled" and "duty cycle == 0" are treated the same */
-	state->duty_cycle = ret;
+	/*
+	 * Note that "disabled" and "duty cycle == 0" are treated the same. If
+	 * the cached duty cycle is not zero, used the cached duty cycle. This
+	 * ensures that the configured duty cycle is kept across a disable and
+	 * enable operation and avoids potentially confusing consumers.
+	 *
+	 * For the case of the initial hardware readout, channel->duty_cycle
+	 * will be 0 and the actual duty cycle read from the EC is used.
+	 */
+	if (ret == 0 && channel->duty_cycle > 0)
+		state->duty_cycle = channel->duty_cycle;
+	else
+		state->duty_cycle = ret;
 }
 
 static struct pwm_device *
@@ -149,6 +197,8 @@ cros_ec_pwm_xlate(struct pwm_chip *pc, const struct of_phandle_args *args)
 }
 
 static const struct pwm_ops cros_ec_pwm_ops = {
+	.request = cros_ec_pwm_request,
+	.free = cros_ec_pwm_free,
 	.get_state	= cros_ec_pwm_get_state,
 	.apply		= cros_ec_pwm_apply,
 	.owner		= THIS_MODULE,
diff --git a/drivers/pwm/pwm-imx27.c b/drivers/pwm/pwm-imx27.c
index ae11d8577f18..35a7ac42269c 100644
--- a/drivers/pwm/pwm-imx27.c
+++ b/drivers/pwm/pwm-imx27.c
@@ -85,6 +85,13 @@ struct pwm_imx27_chip {
 	struct clk	*clk_per;
 	void __iomem	*mmio_base;
 	struct pwm_chip	chip;
+
+	/*
+	 * The driver cannot read the current duty cycle from the hardware if
+	 * the hardware is disabled. Cache the last programmed duty cycle
+	 * value to return in that case.
+	 */
+	unsigned int duty_cycle;
 };
 
 #define to_pwm_imx27_chip(chip)	container_of(chip, struct pwm_imx27_chip, chip)
@@ -155,14 +162,17 @@ static void pwm_imx27_get_state(struct pwm_chip *chip,
 	tmp = NSEC_PER_SEC * (u64)(period + 2);
 	state->period = DIV_ROUND_CLOSEST_ULL(tmp, pwm_clk);
 
-	/* PWMSAR can be read only if PWM is enabled */
-	if (state->enabled) {
+	/*
+	 * PWMSAR can be read only if PWM is enabled. If the PWM is disabled,
+	 * use the cached value.
+	 */
+	if (state->enabled)
 		val = readl(imx->mmio_base + MX3_PWMSAR);
-		tmp = NSEC_PER_SEC * (u64)(val);
-		state->duty_cycle = DIV_ROUND_CLOSEST_ULL(tmp, pwm_clk);
-	} else {
-		state->duty_cycle = 0;
-	}
+	else
+		val = imx->duty_cycle;
+
+	tmp = NSEC_PER_SEC * (u64)(val);
+	state->duty_cycle = DIV_ROUND_CLOSEST_ULL(tmp, pwm_clk);
 
 	if (!state->enabled)
 		pwm_imx27_clk_disable_unprepare(chip);
@@ -220,63 +230,68 @@ static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 
 	pwm_get_state(pwm, &cstate);
 
-	if (state->enabled) {
-		c = clk_get_rate(imx->clk_per);
-		c *= state->period;
-
-		do_div(c, 1000000000);
-		period_cycles = c;
-
-		prescale = period_cycles / 0x10000 + 1;
-
-		period_cycles /= prescale;
-		c = (unsigned long long)period_cycles * state->duty_cycle;
-		do_div(c, state->period);
-		duty_cycles = c;
-
-		/*
-		 * according to imx pwm RM, the real period value should be
-		 * PERIOD value in PWMPR plus 2.
-		 */
-		if (period_cycles > 2)
-			period_cycles -= 2;
-		else
-			period_cycles = 0;
-
-		/*
-		 * Wait for a free FIFO slot if the PWM is already enabled, and
-		 * flush the FIFO if the PWM was disabled and is about to be
-		 * enabled.
-		 */
-		if (cstate.enabled) {
-			pwm_imx27_wait_fifo_slot(chip, pwm);
-		} else {
-			ret = pwm_imx27_clk_prepare_enable(chip);
-			if (ret)
-				return ret;
-
-			pwm_imx27_sw_reset(chip);
-		}
-
-		writel(duty_cycles, imx->mmio_base + MX3_PWMSAR);
-		writel(period_cycles, imx->mmio_base + MX3_PWMPR);
-
-		cr = MX3_PWMCR_PRESCALER_SET(prescale) |
-		     MX3_PWMCR_STOPEN | MX3_PWMCR_DOZEN | MX3_PWMCR_WAITEN |
-		     FIELD_PREP(MX3_PWMCR_CLKSRC, MX3_PWMCR_CLKSRC_IPG_HIGH) |
-		     MX3_PWMCR_DBGEN | MX3_PWMCR_EN;
-
-		if (state->polarity == PWM_POLARITY_INVERSED)
-			cr |= FIELD_PREP(MX3_PWMCR_POUTC,
-					MX3_PWMCR_POUTC_INVERTED);
-
-		writel(cr, imx->mmio_base + MX3_PWMCR);
-	} else if (cstate.enabled) {
-		writel(0, imx->mmio_base + MX3_PWMCR);
+	c = clk_get_rate(imx->clk_per);
+	c *= state->period;
 
-		pwm_imx27_clk_disable_unprepare(chip);
+	do_div(c, 1000000000);
+	period_cycles = c;
+
+	prescale = period_cycles / 0x10000 + 1;
+
+	period_cycles /= prescale;
+	c = (unsigned long long)period_cycles * state->duty_cycle;
+	do_div(c, state->period);
+	duty_cycles = c;
+
+	/*
+	 * according to imx pwm RM, the real period value should be PERIOD
+	 * value in PWMPR plus 2.
+	 */
+	if (period_cycles > 2)
+		period_cycles -= 2;
+	else
+		period_cycles = 0;
+
+	/*
+	 * Wait for a free FIFO slot if the PWM is already enabled, and flush
+	 * the FIFO if the PWM was disabled and is about to be enabled.
+	 */
+	if (cstate.enabled) {
+		pwm_imx27_wait_fifo_slot(chip, pwm);
+	} else {
+		ret = pwm_imx27_clk_prepare_enable(chip);
+		if (ret)
+			return ret;
+
+		pwm_imx27_sw_reset(chip);
 	}
 
+	writel(duty_cycles, imx->mmio_base + MX3_PWMSAR);
+	writel(period_cycles, imx->mmio_base + MX3_PWMPR);
+
+	/*
+	 * Store the duty cycle for future reference in cases where the
+	 * MX3_PWMSAR register can't be read (i.e. when the PWM is disabled).
+	 */
+	imx->duty_cycle = duty_cycles;
+
+	cr = MX3_PWMCR_PRESCALER_SET(prescale) |
+	     MX3_PWMCR_STOPEN | MX3_PWMCR_DOZEN | MX3_PWMCR_WAITEN |
+	     FIELD_PREP(MX3_PWMCR_CLKSRC, MX3_PWMCR_CLKSRC_IPG_HIGH) |
+	     MX3_PWMCR_DBGEN;
+
+	if (state->polarity == PWM_POLARITY_INVERSED)
+		cr |= FIELD_PREP(MX3_PWMCR_POUTC,
+				MX3_PWMCR_POUTC_INVERTED);
+
+	if (state->enabled)
+		cr |= MX3_PWMCR_EN;
+
+	writel(cr, imx->mmio_base + MX3_PWMCR);
+
+	if (!state->enabled && cstate.enabled)
+		pwm_imx27_clk_disable_unprepare(chip);
+
 	return 0;
 }
 
@@ -304,9 +319,13 @@ static int pwm_imx27_probe(struct platform_device *pdev)
 
 	imx->clk_ipg = devm_clk_get(&pdev->dev, "ipg");
 	if (IS_ERR(imx->clk_ipg)) {
-		dev_err(&pdev->dev, "getting ipg clock failed with %ld\n",
-				PTR_ERR(imx->clk_ipg));
-		return PTR_ERR(imx->clk_ipg);
+		int ret = PTR_ERR(imx->clk_ipg);
+
+		if (ret != -EPROBE_DEFER)
+			dev_err(&pdev->dev,
+				"getting ipg clock failed with %d\n",
+				ret);
+		return ret;
 	}
 
 	imx->clk_per = devm_clk_get(&pdev->dev, "per");
diff --git a/drivers/pwm/pwm-mxs.c b/drivers/pwm/pwm-mxs.c
index b14376b47ac8..f2e57fcf8f8b 100644
--- a/drivers/pwm/pwm-mxs.c
+++ b/drivers/pwm/pwm-mxs.c
@@ -25,12 +25,16 @@
 #define  PERIOD_PERIOD(p)	((p) & 0xffff)
 #define  PERIOD_PERIOD_MAX	0x10000
 #define  PERIOD_ACTIVE_HIGH	(3 << 16)
+#define  PERIOD_ACTIVE_LOW	(2 << 16)
+#define  PERIOD_INACTIVE_HIGH	(3 << 18)
 #define  PERIOD_INACTIVE_LOW	(2 << 18)
+#define  PERIOD_POLARITY_NORMAL	(PERIOD_ACTIVE_HIGH | PERIOD_INACTIVE_LOW)
+#define  PERIOD_POLARITY_INVERSE	(PERIOD_ACTIVE_LOW | PERIOD_INACTIVE_HIGH)
 #define  PERIOD_CDIV(div)	(((div) & 0x7) << 20)
 #define  PERIOD_CDIV_MAX	8
 
-static const unsigned int cdiv[PERIOD_CDIV_MAX] = {
-	1, 2, 4, 8, 16, 64, 256, 1024
+static const u8 cdiv_shift[PERIOD_CDIV_MAX] = {
+	0, 1, 2, 3, 4, 6, 8, 10
 };
 
 struct mxs_pwm_chip {
@@ -41,19 +45,34 @@ struct mxs_pwm_chip {
 
 #define to_mxs_pwm_chip(_chip) container_of(_chip, struct mxs_pwm_chip, chip)
 
-static int mxs_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
-			  int duty_ns, int period_ns)
+static int mxs_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			 const struct pwm_state *state)
 {
 	struct mxs_pwm_chip *mxs = to_mxs_pwm_chip(chip);
 	int ret, div = 0;
 	unsigned int period_cycles, duty_cycles;
 	unsigned long rate;
 	unsigned long long c;
+	unsigned int pol_bits;
+
+	/*
+	 * If the PWM channel is disabled, make sure to turn on the
+	 * clock before calling clk_get_rate() and writing to the
+	 * registers. Otherwise, just keep it enabled.
+	 */
+	if (!pwm_is_enabled(pwm)) {
+		ret = clk_prepare_enable(mxs->clk);
+		if (ret)
+			return ret;
+	}
+
+	if (!state->enabled && pwm_is_enabled(pwm))
+		writel(1 << pwm->hwpwm, mxs->base + PWM_CTRL + CLR);
 
 	rate = clk_get_rate(mxs->clk);
 	while (1) {
-		c = rate / cdiv[div];
-		c = c * period_ns;
+		c = rate >> cdiv_shift[div];
+		c = c * state->period;
 		do_div(c, 1000000000);
 		if (c < PERIOD_PERIOD_MAX)
 			break;
@@ -63,62 +82,40 @@ static int mxs_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
 	}
 
 	period_cycles = c;
-	c *= duty_ns;
-	do_div(c, period_ns);
+	c *= state->duty_cycle;
+	do_div(c, state->period);
 	duty_cycles = c;
 
 	/*
-	 * If the PWM channel is disabled, make sure to turn on the clock
-	 * before writing the register. Otherwise, keep it enabled.
+	 * The data sheet the says registers must be written to in
+	 * this order (ACTIVEn, then PERIODn). Also, the new settings
+	 * only take effect at the beginning of a new period, avoiding
+	 * glitches.
 	 */
-	if (!pwm_is_enabled(pwm)) {
-		ret = clk_prepare_enable(mxs->clk);
-		if (ret)
-			return ret;
-	}
 
+	pol_bits = state->polarity == PWM_POLARITY_NORMAL ?
+		PERIOD_POLARITY_NORMAL : PERIOD_POLARITY_INVERSE;
 	writel(duty_cycles << 16,
-			mxs->base + PWM_ACTIVE0 + pwm->hwpwm * 0x20);
-	writel(PERIOD_PERIOD(period_cycles) | PERIOD_ACTIVE_HIGH |
-	       PERIOD_INACTIVE_LOW | PERIOD_CDIV(div),
-			mxs->base + PWM_PERIOD0 + pwm->hwpwm * 0x20);
-
-	/*
-	 * If the PWM is not enabled, turn the clock off again to save power.
-	 */
-	if (!pwm_is_enabled(pwm))
+	       mxs->base + PWM_ACTIVE0 + pwm->hwpwm * 0x20);
+	writel(PERIOD_PERIOD(period_cycles) | pol_bits | PERIOD_CDIV(div),
+	       mxs->base + PWM_PERIOD0 + pwm->hwpwm * 0x20);
+
+	if (state->enabled) {
+		if (!pwm_is_enabled(pwm)) {
+			/*
+			 * The clock was enabled above. Just enable
+			 * the channel in the control register.
+			 */
+			writel(1 << pwm->hwpwm, mxs->base + PWM_CTRL + SET);
+		}
+	} else {
 		clk_disable_unprepare(mxs->clk);
-
-	return 0;
-}
-
-static int mxs_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
-{
-	struct mxs_pwm_chip *mxs = to_mxs_pwm_chip(chip);
-	int ret;
-
-	ret = clk_prepare_enable(mxs->clk);
-	if (ret)
-		return ret;
-
-	writel(1 << pwm->hwpwm, mxs->base + PWM_CTRL + SET);
-
+	}
 	return 0;
 }
 
-static void mxs_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
-{
-	struct mxs_pwm_chip *mxs = to_mxs_pwm_chip(chip);
-
-	writel(1 << pwm->hwpwm, mxs->base + PWM_CTRL + CLR);
-
-	clk_disable_unprepare(mxs->clk);
-}
-
 static const struct pwm_ops mxs_pwm_ops = {
-	.config = mxs_pwm_config,
-	.enable = mxs_pwm_enable,
-	.disable = mxs_pwm_disable,
+	.apply = mxs_pwm_apply,
 	.owner = THIS_MODULE,
 };
 
@@ -142,6 +139,8 @@ static int mxs_pwm_probe(struct platform_device *pdev)
 
 	mxs->chip.dev = &pdev->dev;
 	mxs->chip.ops = &mxs_pwm_ops;
+	mxs->chip.of_xlate = of_pwm_xlate_with_flags;
+	mxs->chip.of_pwm_n_cells = 3;
 	mxs->chip.base = -1;
 
 	ret = of_property_read_u32(np, "fsl,pwm-number", &mxs->chip.npwm);
diff --git a/drivers/pwm/pwm-omap-dmtimer.c b/drivers/pwm/pwm-omap-dmtimer.c
index 00772fc53490..88a3c5690fea 100644
--- a/drivers/pwm/pwm-omap-dmtimer.c
+++ b/drivers/pwm/pwm-omap-dmtimer.c
@@ -256,7 +256,7 @@ static int pwm_omap_dmtimer_probe(struct platform_device *pdev)
 	if (!timer_pdev) {
 		dev_err(&pdev->dev, "Unable to find Timer pdev\n");
 		ret = -ENODEV;
-		goto put;
+		goto err_find_timer_pdev;
 	}
 
 	timer_pdata = dev_get_platdata(&timer_pdev->dev);
@@ -264,7 +264,7 @@ static int pwm_omap_dmtimer_probe(struct platform_device *pdev)
 		dev_dbg(&pdev->dev,
 			 "dmtimer pdata structure NULL, deferring probe\n");
 		ret = -EPROBE_DEFER;
-		goto put;
+		goto err_platdata;
 	}
 
 	pdata = timer_pdata->timer_ops;
@@ -283,30 +283,25 @@ static int pwm_omap_dmtimer_probe(struct platform_device *pdev)
 	    !pdata->write_counter) {
 		dev_err(&pdev->dev, "Incomplete dmtimer pdata structure\n");
 		ret = -EINVAL;
-		goto put;
+		goto err_platdata;
 	}
 
 	if (!of_get_property(timer, "ti,timer-pwm", NULL)) {
 		dev_err(&pdev->dev, "Missing ti,timer-pwm capability\n");
 		ret = -ENODEV;
-		goto put;
+		goto err_timer_property;
 	}
 
 	dm_timer = pdata->request_by_node(timer);
 	if (!dm_timer) {
 		ret = -EPROBE_DEFER;
-		goto put;
+		goto err_request_timer;
 	}
 
-put:
-	of_node_put(timer);
-	if (ret < 0)
-		return ret;
-
 	omap = devm_kzalloc(&pdev->dev, sizeof(*omap), GFP_KERNEL);
 	if (!omap) {
-		pdata->free(dm_timer);
-		return -ENOMEM;
+		ret = -ENOMEM;
+		goto err_alloc_omap;
 	}
 
 	omap->pdata = pdata;
@@ -339,27 +334,56 @@ put:
 	ret = pwmchip_add(&omap->chip);
 	if (ret < 0) {
 		dev_err(&pdev->dev, "failed to register PWM\n");
-		omap->pdata->free(omap->dm_timer);
-		return ret;
+		goto err_pwmchip_add;
 	}
 
+	of_node_put(timer);
+
 	platform_set_drvdata(pdev, omap);
 
 	return 0;
+
+err_pwmchip_add:
+
+	/*
+	 * *omap is allocated using devm_kzalloc,
+	 * so no free necessary here
+	 */
+err_alloc_omap:
+
+	pdata->free(dm_timer);
+err_request_timer:
+
+err_timer_property:
+err_platdata:
+
+	put_device(&timer_pdev->dev);
+err_find_timer_pdev:
+
+	of_node_put(timer);
+
+	return ret;
 }
 
 static int pwm_omap_dmtimer_remove(struct platform_device *pdev)
 {
 	struct pwm_omap_dmtimer_chip *omap = platform_get_drvdata(pdev);
+	int ret;
+
+	ret = pwmchip_remove(&omap->chip);
+	if (ret)
+		return ret;
 
 	if (pm_runtime_active(&omap->dm_timer_pdev->dev))
 		omap->pdata->stop(omap->dm_timer);
 
 	omap->pdata->free(omap->dm_timer);
 
+	put_device(&omap->dm_timer_pdev->dev);
+
 	mutex_destroy(&omap->mutex);
 
-	return pwmchip_remove(&omap->chip);
+	return 0;
 }
 
 static const struct of_device_id pwm_omap_dmtimer_of_match[] = {
diff --git a/drivers/pwm/pwm-pca9685.c b/drivers/pwm/pwm-pca9685.c
index 168684b02ebc..b07bdca3d510 100644
--- a/drivers/pwm/pwm-pca9685.c
+++ b/drivers/pwm/pwm-pca9685.c
@@ -159,13 +159,9 @@ static void pca9685_pwm_gpio_set(struct gpio_chip *gpio, unsigned int offset,
 static void pca9685_pwm_gpio_free(struct gpio_chip *gpio, unsigned int offset)
 {
 	struct pca9685 *pca = gpiochip_get_data(gpio);
-	struct pwm_device *pwm;
 
 	pca9685_pwm_gpio_set(gpio, offset, 0);
 	pm_runtime_put(pca->chip.dev);
-	mutex_lock(&pca->lock);
-	pwm = &pca->chip.pwms[offset];
-	mutex_unlock(&pca->lock);
 }
 
 static int pca9685_pwm_gpio_get_direction(struct gpio_chip *chip,
diff --git a/drivers/pwm/pwm-rcar.c b/drivers/pwm/pwm-rcar.c
index 852eb2347954..2685577b6dd4 100644
--- a/drivers/pwm/pwm-rcar.c
+++ b/drivers/pwm/pwm-rcar.c
@@ -3,6 +3,9 @@
  * R-Car PWM Timer driver
  *
  * Copyright (C) 2015 Renesas Electronics Corporation
+ *
+ * Limitations:
+ * - The hardware cannot generate a 0% duty cycle.
  */
 
 #include <linux/clk.h>
@@ -161,11 +164,9 @@ static int rcar_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 			  const struct pwm_state *state)
 {
 	struct rcar_pwm_chip *rp = to_rcar_pwm_chip(chip);
-	struct pwm_state cur_state;
 	int div, ret;
 
 	/* This HW/driver only supports normal polarity */
-	pwm_get_state(pwm, &cur_state);
 	if (state->polarity != PWM_POLARITY_NORMAL)
 		return -ENOTSUPP;
 
diff --git a/drivers/pwm/pwm-stm32.c b/drivers/pwm/pwm-stm32.c
index 7ff48c14fae8..d3be944f2ae9 100644
--- a/drivers/pwm/pwm-stm32.c
+++ b/drivers/pwm/pwm-stm32.c
@@ -377,9 +377,7 @@ static int stm32_pwm_config(struct stm32_pwm *priv, int ch,
 	else
 		regmap_update_bits(priv->regmap, TIM_CCMR2, mask, ccmr);
 
-	regmap_update_bits(priv->regmap, TIM_BDTR,
-			   TIM_BDTR_MOE | TIM_BDTR_AOE,
-			   TIM_BDTR_MOE | TIM_BDTR_AOE);
+	regmap_update_bits(priv->regmap, TIM_BDTR, TIM_BDTR_MOE, TIM_BDTR_MOE);
 
 	return 0;
 }
diff --git a/drivers/pwm/pwm-sun4i.c b/drivers/pwm/pwm-sun4i.c
index 581d23287333..3e3efa6c768f 100644
--- a/drivers/pwm/pwm-sun4i.c
+++ b/drivers/pwm/pwm-sun4i.c
@@ -3,6 +3,10 @@
  * Driver for Allwinner sun4i Pulse Width Modulation Controller
  *
  * Copyright (C) 2014 Alexandre Belloni <alexandre.belloni@free-electrons.com>
+ *
+ * Limitations:
+ * - When outputing the source clock directly, the PWM logic will be bypassed
+ *   and the currently running period is not guaranteed to be completed
  */
 
 #include <linux/bitops.h>
@@ -16,6 +20,7 @@
 #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>
@@ -72,12 +77,15 @@ static const u32 prescaler_table[] = {
 
 struct sun4i_pwm_data {
 	bool has_prescaler_bypass;
+	bool has_direct_mod_clk_output;
 	unsigned int npwm;
 };
 
 struct sun4i_pwm_chip {
 	struct pwm_chip chip;
+	struct clk *bus_clk;
 	struct clk *clk;
+	struct reset_control *rst;
 	void __iomem *base;
 	spinlock_t ctrl_lock;
 	const struct sun4i_pwm_data *data;
@@ -115,6 +123,20 @@ static void sun4i_pwm_get_state(struct pwm_chip *chip,
 
 	val = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG);
 
+	/*
+	 * PWM chapter in H6 manual has a diagram which explains that if bypass
+	 * bit is set, no other setting has any meaning. Even more, experiment
+	 * proved that also enable bit is ignored in this case.
+	 */
+	if ((val & BIT_CH(PWM_BYPASS, pwm->hwpwm)) &&
+	    sun4i_pwm->data->has_direct_mod_clk_output) {
+		state->period = DIV_ROUND_UP_ULL(NSEC_PER_SEC, clk_rate);
+		state->duty_cycle = DIV_ROUND_UP_ULL(state->period, 2);
+		state->polarity = PWM_POLARITY_NORMAL;
+		state->enabled = true;
+		return;
+	}
+
 	if ((PWM_REG_PRESCAL(val, pwm->hwpwm) == PWM_PRESCAL_MASK) &&
 	    sun4i_pwm->data->has_prescaler_bypass)
 		prescaler = 1;
@@ -146,13 +168,24 @@ static void sun4i_pwm_get_state(struct pwm_chip *chip,
 
 static int sun4i_pwm_calculate(struct sun4i_pwm_chip *sun4i_pwm,
 			       const struct pwm_state *state,
-			       u32 *dty, u32 *prd, unsigned int *prsclr)
+			       u32 *dty, u32 *prd, unsigned int *prsclr,
+			       bool *bypass)
 {
 	u64 clk_rate, div = 0;
-	unsigned int pval, prescaler = 0;
+	unsigned int prescaler = 0;
 
 	clk_rate = clk_get_rate(sun4i_pwm->clk);
 
+	*bypass = sun4i_pwm->data->has_direct_mod_clk_output &&
+		  state->enabled &&
+		  (state->period * clk_rate >= NSEC_PER_SEC) &&
+		  (state->period * clk_rate < 2 * NSEC_PER_SEC) &&
+		  (state->duty_cycle * clk_rate * 2 >= NSEC_PER_SEC);
+
+	/* Skip calculation of other parameters if we bypass them */
+	if (*bypass)
+		return 0;
+
 	if (sun4i_pwm->data->has_prescaler_bypass) {
 		/* First, test without any prescaler when available */
 		prescaler = PWM_PRESCAL_MASK;
@@ -170,9 +203,11 @@ static int sun4i_pwm_calculate(struct sun4i_pwm_chip *sun4i_pwm,
 	if (prescaler == 0) {
 		/* Go up from the first divider */
 		for (prescaler = 0; prescaler < PWM_PRESCAL_MASK; prescaler++) {
-			if (!prescaler_table[prescaler])
+			unsigned int pval = prescaler_table[prescaler];
+
+			if (!pval)
 				continue;
-			pval = prescaler_table[prescaler];
+
 			div = clk_rate;
 			do_div(div, pval);
 			div = div * state->period;
@@ -199,10 +234,11 @@ static int sun4i_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 {
 	struct sun4i_pwm_chip *sun4i_pwm = to_sun4i_pwm_chip(chip);
 	struct pwm_state cstate;
-	u32 ctrl;
+	u32 ctrl, duty = 0, period = 0, val;
 	int ret;
-	unsigned int delay_us;
+	unsigned int delay_us, prescaler = 0;
 	unsigned long now;
+	bool bypass;
 
 	pwm_get_state(pwm, &cstate);
 
@@ -214,46 +250,52 @@ static int sun4i_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 		}
 	}
 
+	ret = sun4i_pwm_calculate(sun4i_pwm, state, &duty, &period, &prescaler,
+				  &bypass);
+	if (ret) {
+		dev_err(chip->dev, "period exceeds the maximum value\n");
+		if (!cstate.enabled)
+			clk_disable_unprepare(sun4i_pwm->clk);
+		return ret;
+	}
+
 	spin_lock(&sun4i_pwm->ctrl_lock);
 	ctrl = sun4i_pwm_readl(sun4i_pwm, PWM_CTRL_REG);
 
-	if ((cstate.period != state->period) ||
-	    (cstate.duty_cycle != state->duty_cycle)) {
-		u32 period, duty, val;
-		unsigned int prescaler;
-
-		ret = sun4i_pwm_calculate(sun4i_pwm, state,
-					  &duty, &period, &prescaler);
-		if (ret) {
-			dev_err(chip->dev, "period exceeds the maximum value\n");
+	if (sun4i_pwm->data->has_direct_mod_clk_output) {
+		if (bypass) {
+			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);
-			if (!cstate.enabled)
-				clk_disable_unprepare(sun4i_pwm->clk);
-			return ret;
+			return 0;
 		}
 
-		if (PWM_REG_PRESCAL(ctrl, pwm->hwpwm) != prescaler) {
-			/* Prescaler changed, the clock has to be gated */
-			ctrl &= ~BIT_CH(PWM_CLK_GATING, pwm->hwpwm);
-			sun4i_pwm_writel(sun4i_pwm, ctrl, PWM_CTRL_REG);
+		ctrl &= ~BIT_CH(PWM_BYPASS, pwm->hwpwm);
+	}
 
-			ctrl &= ~BIT_CH(PWM_PRESCAL_MASK, pwm->hwpwm);
-			ctrl |= BIT_CH(prescaler, pwm->hwpwm);
-		}
+	if (PWM_REG_PRESCAL(ctrl, pwm->hwpwm) != prescaler) {
+		/* Prescaler changed, the clock has to be gated */
+		ctrl &= ~BIT_CH(PWM_CLK_GATING, pwm->hwpwm);
+		sun4i_pwm_writel(sun4i_pwm, ctrl, PWM_CTRL_REG);
 
-		val = (duty & PWM_DTY_MASK) | PWM_PRD(period);
-		sun4i_pwm_writel(sun4i_pwm, val, PWM_CH_PRD(pwm->hwpwm));
-		sun4i_pwm->next_period[pwm->hwpwm] = jiffies +
-			usecs_to_jiffies(cstate.period / 1000 + 1);
-		sun4i_pwm->needs_delay[pwm->hwpwm] = true;
+		ctrl &= ~BIT_CH(PWM_PRESCAL_MASK, pwm->hwpwm);
+		ctrl |= BIT_CH(prescaler, pwm->hwpwm);
 	}
 
+	val = (duty & PWM_DTY_MASK) | PWM_PRD(period);
+	sun4i_pwm_writel(sun4i_pwm, val, PWM_CH_PRD(pwm->hwpwm));
+	sun4i_pwm->next_period[pwm->hwpwm] = jiffies +
+		usecs_to_jiffies(cstate.period / 1000 + 1);
+	sun4i_pwm->needs_delay[pwm->hwpwm] = true;
+
 	if (state->polarity != PWM_POLARITY_NORMAL)
 		ctrl &= ~BIT_CH(PWM_ACT_STATE, pwm->hwpwm);
 	else
 		ctrl |= BIT_CH(PWM_ACT_STATE, pwm->hwpwm);
 
 	ctrl |= BIT_CH(PWM_CLK_GATING, pwm->hwpwm);
+
 	if (state->enabled) {
 		ctrl |= BIT_CH(PWM_EN, pwm->hwpwm);
 	} else if (!sun4i_pwm->needs_delay[pwm->hwpwm]) {
@@ -319,6 +361,12 @@ static const struct sun4i_pwm_data sun4i_pwm_single_bypass = {
 	.npwm = 1,
 };
 
+static const struct sun4i_pwm_data sun50i_h6_pwm_data = {
+	.has_prescaler_bypass = true,
+	.has_direct_mod_clk_output = true,
+	.npwm = 2,
+};
+
 static const struct of_device_id sun4i_pwm_dt_ids[] = {
 	{
 		.compatible = "allwinner,sun4i-a10-pwm",
@@ -336,6 +384,9 @@ static const struct of_device_id sun4i_pwm_dt_ids[] = {
 		.compatible = "allwinner,sun8i-h3-pwm",
 		.data = &sun4i_pwm_single_bypass,
 	}, {
+		.compatible = "allwinner,sun50i-h6-pwm",
+		.data = &sun50i_h6_pwm_data,
+	}, {
 		/* sentinel */
 	},
 };
@@ -360,9 +411,69 @@ static int sun4i_pwm_probe(struct platform_device *pdev)
 	if (IS_ERR(pwm->base))
 		return PTR_ERR(pwm->base);
 
-	pwm->clk = devm_clk_get(&pdev->dev, NULL);
-	if (IS_ERR(pwm->clk))
+	/*
+	 * All hardware variants need a source clock that is divided and
+	 * then feeds the counter that defines the output wave form. In the
+	 * device tree this clock is either unnamed or called "mod".
+	 * Some variants (e.g. H6) need another clock to access the
+	 * hardware registers; this is called "bus".
+	 * So we request "mod" first (and ignore the corner case that a
+	 * parent provides a "mod" clock while the right one would be the
+	 * unnamed one of the PWM device) and if this is not found we fall
+	 * back to the first clock of the PWM.
+	 */
+	pwm->clk = devm_clk_get_optional(&pdev->dev, "mod");
+	if (IS_ERR(pwm->clk)) {
+		if (PTR_ERR(pwm->clk) != -EPROBE_DEFER)
+			dev_err(&pdev->dev, "get mod clock failed %pe\n",
+				pwm->clk);
 		return PTR_ERR(pwm->clk);
+	}
+
+	if (!pwm->clk) {
+		pwm->clk = devm_clk_get(&pdev->dev, NULL);
+		if (IS_ERR(pwm->clk)) {
+			if (PTR_ERR(pwm->clk) != -EPROBE_DEFER)
+				dev_err(&pdev->dev, "get unnamed clock failed %pe\n",
+					pwm->clk);
+			return PTR_ERR(pwm->clk);
+		}
+	}
+
+	pwm->bus_clk = devm_clk_get_optional(&pdev->dev, "bus");
+	if (IS_ERR(pwm->bus_clk)) {
+		if (PTR_ERR(pwm->bus_clk) != -EPROBE_DEFER)
+			dev_err(&pdev->dev, "get bus clock failed %pe\n",
+				pwm->bus_clk);
+		return PTR_ERR(pwm->bus_clk);
+	}
+
+	pwm->rst = devm_reset_control_get_optional_shared(&pdev->dev, NULL);
+	if (IS_ERR(pwm->rst)) {
+		if (PTR_ERR(pwm->rst) != -EPROBE_DEFER)
+			dev_err(&pdev->dev, "get reset failed %pe\n",
+				pwm->rst);
+		return PTR_ERR(pwm->rst);
+	}
+
+	/* Deassert reset */
+	ret = reset_control_deassert(pwm->rst);
+	if (ret) {
+		dev_err(&pdev->dev, "cannot deassert reset control: %pe\n",
+			ERR_PTR(ret));
+		return ret;
+	}
+
+	/*
+	 * We're keeping the bus clock on for the sake of simplicity.
+	 * Actually it only needs to be on for hardware register accesses.
+	 */
+	ret = clk_prepare_enable(pwm->bus_clk);
+	if (ret) {
+		dev_err(&pdev->dev, "cannot prepare and enable bus_clk %pe\n",
+			ERR_PTR(ret));
+		goto err_bus;
+	}
 
 	pwm->chip.dev = &pdev->dev;
 	pwm->chip.ops = &sun4i_pwm_ops;
@@ -376,19 +487,34 @@ static int sun4i_pwm_probe(struct platform_device *pdev)
 	ret = pwmchip_add(&pwm->chip);
 	if (ret < 0) {
 		dev_err(&pdev->dev, "failed to add PWM chip: %d\n", ret);
-		return ret;
+		goto err_pwm_add;
 	}
 
 	platform_set_drvdata(pdev, pwm);
 
 	return 0;
+
+err_pwm_add:
+	clk_disable_unprepare(pwm->bus_clk);
+err_bus:
+	reset_control_assert(pwm->rst);
+
+	return ret;
 }
 
 static int sun4i_pwm_remove(struct platform_device *pdev)
 {
 	struct sun4i_pwm_chip *pwm = platform_get_drvdata(pdev);
+	int ret;
+
+	ret = pwmchip_remove(&pwm->chip);
+	if (ret)
+		return ret;
+
+	clk_disable_unprepare(pwm->bus_clk);
+	reset_control_assert(pwm->rst);
 
-	return pwmchip_remove(&pwm->chip);
+	return 0;
 }
 
 static struct platform_driver sun4i_pwm_driver = {