Merge branch 'for-4.7/pwm-atomic' into for-next

Documentation/pwm.txt

@@ -42,9 +42,26 @@ variants of these functions, devm_pwm_get() and devm_pwm_put(), also exist.
 
 After being requested, a PWM has to be configured using:
 
-int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns);
+int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state);
 
-To start/stop toggling the PWM output use pwm_enable()/pwm_disable().
+This API controls both the PWM period/duty_cycle config and the
+enable/disable state.
+
+The pwm_config(), pwm_enable() and pwm_disable() functions are just wrappers
+around pwm_apply_state() and should not be used if the user wants to change
+several parameter at once. For example, if you see pwm_config() and
+pwm_{enable,disable}() calls in the same function, this probably means you
+should switch to pwm_apply_state().
+
+The PWM user API also allows one to query the PWM state with pwm_get_state().
+
+In addition to the PWM state, the PWM API also exposes PWM arguments, which
+are the reference PWM config one should use on this PWM.
+PWM arguments are usually platform-specific and allows the PWM user to only
+care about dutycycle relatively to the full period (like, duty = 50% of the
+period). struct pwm_args contains 2 fields (period and polarity) and should
+be used to set the initial PWM config (usually done in the probe function
+of the PWM user). PWM arguments are retrieved with pwm_get_args().
 
 Using PWMs with the sysfs interface
 -----------------------------------
@@ -105,6 +122,15 @@ goes low for the remainder of the period. Conversely, a signal with inversed
 polarity starts low for the duration of the duty cycle and goes high for the
 remainder of the period.
 
+Drivers are encouraged to implement ->apply() instead of the legacy
+->enable(), ->disable() and ->config() methods. Doing that should provide
+atomicity in the PWM config workflow, which is required when the PWM controls
+a critical device (like a regulator).
+
+The implementation of ->get_state() (a method used to retrieve initial PWM
+state) is also encouraged for the same reason: letting the PWM user know
+about the current PWM state would allow him to avoid glitches.
+
 Locking
 -------
 

arch/arm/mach-s3c24xx/mach-rx1950.c

@@ -496,6 +496,12 @@ static int rx1950_backlight_init(struct device *dev)
 		return PTR_ERR(lcd_pwm);
 	}
 
+	/*
+	 * FIXME: pwm_apply_args() should be removed when switching to
+	 * the atomic PWM API.
+	 */
+	pwm_apply_args(lcd_pwm);
+
 	rx1950_lcd_power(1);
 	rx1950_bl_power(1);
 

drivers/clk/clk-pwm.c

@@ -59,6 +59,7 @@ static int clk_pwm_probe(struct platform_device *pdev)
 	struct clk_init_data init;
 	struct clk_pwm *clk_pwm;
 	struct pwm_device *pwm;
+	struct pwm_args pargs;
 	const char *clk_name;
 	struct clk *clk;
 	int ret;
@@ -71,22 +72,28 @@ static int clk_pwm_probe(struct platform_device *pdev)
 	if (IS_ERR(pwm))
 		return PTR_ERR(pwm);
 
-	if (!pwm->period) {
+	pwm_get_args(pwm, &pargs);
+	if (!pargs.period) {
 		dev_err(&pdev->dev, "invalid PWM period\n");
 		return -EINVAL;
 	}
 
 	if (of_property_read_u32(node, "clock-frequency", &clk_pwm->fixed_rate))
-		clk_pwm->fixed_rate = NSEC_PER_SEC / pwm->period;
+		clk_pwm->fixed_rate = NSEC_PER_SEC / pargs.period;
 
-	if (pwm->period != NSEC_PER_SEC / clk_pwm->fixed_rate &&
-	    pwm->period != DIV_ROUND_UP(NSEC_PER_SEC, clk_pwm->fixed_rate)) {
+	if (pargs.period != NSEC_PER_SEC / clk_pwm->fixed_rate &&
+	    pargs.period != DIV_ROUND_UP(NSEC_PER_SEC, clk_pwm->fixed_rate)) {
 		dev_err(&pdev->dev,
 			"clock-frequency does not match PWM period\n");
 		return -EINVAL;
 	}
 
-	ret = pwm_config(pwm, (pwm->period + 1) >> 1, pwm->period);
+	/*
+	 * FIXME: pwm_apply_args() should be removed when switching to the
+	 * atomic PWM API.
+	 */
+	pwm_apply_args(pwm);
+	ret = pwm_config(pwm, (pargs.period + 1) >> 1, pargs.period);
 	if (ret < 0)
 		return ret;
 

drivers/gpu/drm/i915/intel_panel.c

@@ -1640,6 +1640,12 @@ static int pwm_setup_backlight(struct intel_connector *connector,
 		return -ENODEV;
 	}
 
+	/*
+	 * FIXME: pwm_apply_args() should be removed when switching to
+	 * the atomic PWM API.
+	 */
+	pwm_apply_args(panel->backlight.pwm);
+
 	retval = pwm_config(panel->backlight.pwm, CRC_PMIC_PWM_PERIOD_NS,
 			    CRC_PMIC_PWM_PERIOD_NS);
 	if (retval < 0) {

drivers/hwmon/pwm-fan.c

@@ -40,15 +40,18 @@ struct pwm_fan_ctx {
 
 static int  __set_pwm(struct pwm_fan_ctx *ctx, unsigned long pwm)
 {
+	struct pwm_args pargs;
 	unsigned long duty;
 	int ret = 0;
 
+	pwm_get_args(ctx->pwm, &pargs);
+
 	mutex_lock(&ctx->lock);
 	if (ctx->pwm_value == pwm)
 		goto exit_set_pwm_err;
 
-	duty = DIV_ROUND_UP(pwm * (ctx->pwm->period - 1), MAX_PWM);
-	ret = pwm_config(ctx->pwm, duty, ctx->pwm->period);
+	duty = DIV_ROUND_UP(pwm * (pargs.period - 1), MAX_PWM);
+	ret = pwm_config(ctx->pwm, duty, pargs.period);
 	if (ret)
 		goto exit_set_pwm_err;
 
@@ -215,6 +218,7 @@ static int pwm_fan_probe(struct platform_device *pdev)
 {
 	struct thermal_cooling_device *cdev;
 	struct pwm_fan_ctx *ctx;
+	struct pwm_args pargs;
 	struct device *hwmon;
 	int duty_cycle;
 	int ret;
@@ -233,11 +237,19 @@ static int pwm_fan_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, ctx);
 
+	/*
+	 * FIXME: pwm_apply_args() should be removed when switching to the
+	 * atomic PWM API.
+	 */
+	pwm_apply_args(ctx->pwm);
+
 	/* Set duty cycle to maximum allowed */
-	duty_cycle = ctx->pwm->period - 1;
+	pwm_get_args(ctx->pwm, &pargs);
+
+	duty_cycle = pargs.period - 1;
 	ctx->pwm_value = MAX_PWM;
 
-	ret = pwm_config(ctx->pwm, duty_cycle, ctx->pwm->period);
+	ret = pwm_config(ctx->pwm, duty_cycle, pargs.period);
 	if (ret) {
 		dev_err(&pdev->dev, "Failed to configure PWM\n");
 		return ret;
@@ -303,14 +315,16 @@ static int pwm_fan_suspend(struct device *dev)
 static int pwm_fan_resume(struct device *dev)
 {
 	struct pwm_fan_ctx *ctx = dev_get_drvdata(dev);
+	struct pwm_args pargs;
 	unsigned long duty;
 	int ret;
 
 	if (ctx->pwm_value == 0)
 		return 0;
 
-	duty = DIV_ROUND_UP(ctx->pwm_value * (ctx->pwm->period - 1), MAX_PWM);
-	ret = pwm_config(ctx->pwm, duty, ctx->pwm->period);
+	pwm_get_args(ctx->pwm, &pargs);
+	duty = DIV_ROUND_UP(ctx->pwm_value * (pargs.period - 1), MAX_PWM);
+	ret = pwm_config(ctx->pwm, duty, pargs.period);
 	if (ret)
 		return ret;
 	return pwm_enable(ctx->pwm);

drivers/input/misc/max77693-haptic.c

@@ -70,10 +70,13 @@ struct max77693_haptic {
 
 static int max77693_haptic_set_duty_cycle(struct max77693_haptic *haptic)
 {
-	int delta = (haptic->pwm_dev->period + haptic->pwm_duty) / 2;
+	struct pwm_args pargs;
+	int delta;
 	int error;
 
-	error = pwm_config(haptic->pwm_dev, delta, haptic->pwm_dev->period);
+	pwm_get_args(haptic->pwm_dev, &pargs);
+	delta = (pargs.period + haptic->pwm_duty) / 2;
+	error = pwm_config(haptic->pwm_dev, delta, pargs.period);
 	if (error) {
 		dev_err(haptic->dev, "failed to configure pwm: %d\n", error);
 		return error;
@@ -234,6 +237,7 @@ static int max77693_haptic_play_effect(struct input_dev *dev, void *data,
 				       struct ff_effect *effect)
 {
 	struct max77693_haptic *haptic = input_get_drvdata(dev);
+	struct pwm_args pargs;
 	u64 period_mag_multi;
 
 	haptic->magnitude = effect->u.rumble.strong_magnitude;
@@ -245,7 +249,8 @@ static int max77693_haptic_play_effect(struct input_dev *dev, void *data,
 	 * The formula to convert magnitude to pwm_duty as follows:
 	 * - pwm_duty = (magnitude * pwm_period) / MAX_MAGNITUDE(0xFFFF)
 	 */
-	period_mag_multi = (u64)haptic->pwm_dev->period * haptic->magnitude;
+	pwm_get_args(haptic->pwm_dev, &pargs);
+	period_mag_multi = (u64)pargs.period * haptic->magnitude;
 	haptic->pwm_duty = (unsigned int)(period_mag_multi >>
 						MAX_MAGNITUDE_SHIFT);
 
@@ -329,6 +334,12 @@ static int max77693_haptic_probe(struct platform_device *pdev)
 		return PTR_ERR(haptic->pwm_dev);
 	}
 
+	/*
+	 * FIXME: pwm_apply_args() should be removed when switching to the
+	 * atomic PWM API.
+	 */
+	pwm_apply_args(haptic->pwm_dev);
+
 	haptic->motor_reg = devm_regulator_get(&pdev->dev, "haptic");
 	if (IS_ERR(haptic->motor_reg)) {
 		dev_err(&pdev->dev, "failed to get regulator\n");

drivers/input/misc/max8997_haptic.c

@@ -304,6 +304,12 @@ static int max8997_haptic_probe(struct platform_device *pdev)
 				error);
 			goto err_free_mem;
 		}
+
+		/*
+		 * FIXME: pwm_apply_args() should be removed when switching to
+		 * the atomic PWM API.
+		 */
+		pwm_apply_args(chip->pwm);
 		break;
 
 	default:

drivers/input/misc/pwm-beeper.c

@@ -87,6 +87,12 @@ static int pwm_beeper_probe(struct platform_device *pdev)
 		goto err_free;
 	}
 
+	/*
+	 * FIXME: pwm_apply_args() should be removed when switching to
+	 * the atomic PWM API.
+	 */
+	pwm_apply_args(beeper->pwm);
+
 	beeper->input = input_allocate_device();
 	if (!beeper->input) {
 		dev_err(&pdev->dev, "Failed to allocate input device\n");

drivers/leds/leds-pwm.c

@@ -91,6 +91,7 @@ static int led_pwm_add(struct device *dev, struct led_pwm_priv *priv,
 		       struct led_pwm *led, struct device_node *child)
 {
 	struct led_pwm_data *led_data = &priv->leds[priv->num_leds];
+	struct pwm_args pargs;
 	int ret;
 
 	led_data->active_low = led->active_low;
@@ -117,7 +118,15 @@ static int led_pwm_add(struct device *dev, struct led_pwm_priv *priv,
 	else
 		led_data->cdev.brightness_set_blocking = led_pwm_set_blocking;
 
-	led_data->period = pwm_get_period(led_data->pwm);
+	/*
+	 * FIXME: pwm_apply_args() should be removed when switching to the
+	 * atomic PWM API.
+	 */
+	pwm_apply_args(led_data->pwm);
+
+	pwm_get_args(led_data->pwm, &pargs);
+
+	led_data->period = pargs.period;
 	if (!led_data->period && (led->pwm_period_ns > 0))
 		led_data->period = led->pwm_period_ns;
 

drivers/pwm/core.c

@@ -227,6 +227,19 @@ void *pwm_get_chip_data(struct pwm_device *pwm)
 }
 EXPORT_SYMBOL_GPL(pwm_get_chip_data);
 
+static bool pwm_ops_check(const struct pwm_ops *ops)
+{
+	/* driver supports legacy, non-atomic operation */
+	if (ops->config && ops->enable && ops->disable)
+		return true;
+
+	/* driver supports atomic operation */
+	if (ops->apply)
+		return true;
+
+	return false;
+}
+
 /**
  * pwmchip_add_with_polarity() - register a new PWM chip
  * @chip: the PWM chip to add
@@ -245,8 +258,10 @@ int pwmchip_add_with_polarity(struct pwm_chip *chip,
 	unsigned int i;
 	int ret;
 
-	if (!chip || !chip->dev || !chip->ops || !chip->ops->config ||
-	    !chip->ops->enable || !chip->ops->disable || !chip->npwm)
+	if (!chip || !chip->dev || !chip->ops || !chip->npwm)
+		return -EINVAL;
+
+	if (!pwm_ops_check(chip->ops))
 		return -EINVAL;
 
 	mutex_lock(&pwm_lock);
@@ -269,8 +284,10 @@ int pwmchip_add_with_polarity(struct pwm_chip *chip,
 		pwm->chip = chip;
 		pwm->pwm = chip->base + i;
 		pwm->hwpwm = i;
-		pwm->polarity = polarity;
-		mutex_init(&pwm->lock);
+		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);
 	}
@@ -430,107 +447,138 @@ void pwm_free(struct pwm_device *pwm)
 EXPORT_SYMBOL_GPL(pwm_free);
 
 /**
- * pwm_config() - change a PWM device configuration
+ * pwm_apply_state() - atomically apply a new state to a PWM device
  * @pwm: PWM device
- * @duty_ns: "on" time (in nanoseconds)
- * @period_ns: duration (in nanoseconds) of one cycle
- *
- * Returns: 0 on success or a negative error code on failure.
+ * @state: new state to apply. This can be adjusted by the PWM driver
+ *	   if the requested config is not achievable, for example,
+ *	   ->duty_cycle and ->period might be approximated.
  */
-int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)
+int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state)
 {
 	int err;
 
-	if (!pwm || duty_ns < 0 || period_ns <= 0 || duty_ns > period_ns)
+	if (!pwm)
 		return -EINVAL;
 
-	err = pwm->chip->ops->config(pwm->chip, pwm, duty_ns, period_ns);
+	if (!memcmp(state, &pwm->state, sizeof(*state)))
+		return 0;
+
+	if (pwm->chip->ops->apply) {
+		err = pwm->chip->ops->apply(pwm->chip, pwm, state);
 		if (err)
 			return err;
 
-	pwm->duty_cycle = duty_ns;
-	pwm->period = period_ns;
-
-	return 0;
-}
-EXPORT_SYMBOL_GPL(pwm_config);
+		pwm->state = *state;
+	} else {
+		/*
+		 * FIXME: restore the initial state in case of error.
+		 */
+		if (state->polarity != pwm->state.polarity) {
+			if (!pwm->chip->ops->set_polarity)
+				return -ENOTSUPP;
 
-/**
- * pwm_set_polarity() - configure the polarity of a PWM signal
- * @pwm: PWM device
- * @polarity: new polarity of the PWM signal
- *
- * Note that the polarity cannot be configured while the PWM device is
- * enabled.
- *
- * Returns: 0 on success or a negative error code on failure.
+			/*
+			 * Changing the polarity of a running PWM is
+			 * only allowed when the PWM driver implements
+			 * ->apply().
 			 */
-int pwm_set_polarity(struct pwm_device *pwm, enum pwm_polarity polarity)
-{
-	int err;
+			if (pwm->state.enabled) {
+				pwm->chip->ops->disable(pwm->chip, pwm);
+				pwm->state.enabled = false;
+			}
 
-	if (!pwm || !pwm->chip->ops)
-		return -EINVAL;
+			err = pwm->chip->ops->set_polarity(pwm->chip, pwm,
+							   state->polarity);
+			if (err)
+				return err;
 
-	if (!pwm->chip->ops->set_polarity)
-		return -ENOSYS;
+			pwm->state.polarity = state->polarity;
+		}
 
-	mutex_lock(&pwm->lock);
+		if (state->period != pwm->state.period ||
+		    state->duty_cycle != pwm->state.duty_cycle) {
+			err = pwm->chip->ops->config(pwm->chip, pwm,
+						     state->duty_cycle,
+						     state->period);
+			if (err)
+				return err;
 
-	if (pwm_is_enabled(pwm)) {
-		err = -EBUSY;
-		goto unlock;
+			pwm->state.duty_cycle = state->duty_cycle;
+			pwm->state.period = state->period;
 		}
 
-	err = pwm->chip->ops->set_polarity(pwm->chip, pwm, polarity);
+		if (state->enabled != pwm->state.enabled) {
+			if (state->enabled) {
+				err = pwm->chip->ops->enable(pwm->chip, pwm);
 				if (err)
-		goto unlock;
+					return err;
+			} else {
+				pwm->chip->ops->disable(pwm->chip, pwm);
+			}
 
-	pwm->polarity = polarity;
+			pwm->state.enabled = state->enabled;
+		}
+	}
 
-unlock:
-	mutex_unlock(&pwm->lock);
-	return err;
+	return 0;
 }
-EXPORT_SYMBOL_GPL(pwm_set_polarity);
+EXPORT_SYMBOL_GPL(pwm_apply_state);
 
 /**
- * pwm_enable() - start a PWM output toggling
+ * pwm_adjust_config() - adjust the current PWM config to the PWM arguments
  * @pwm: PWM device
  *
- * Returns: 0 on success or a negative error code on failure.
+ * This function will adjust the PWM config to the PWM arguments provided
+ * by the DT or PWM lookup table. This is particularly useful to adapt
+ * the bootloader config to the Linux one.
  */
-int pwm_enable(struct pwm_device *pwm)
+int pwm_adjust_config(struct pwm_device *pwm)
 {
-	int err = 0;
+	struct pwm_state state;
+	struct pwm_args pargs;
 
-	if (!pwm)
-		return -EINVAL;
+	pwm_get_args(pwm, &pargs);
+	pwm_get_state(pwm, &state);
 
-	mutex_lock(&pwm->lock);
+	/*
+	 * If the current period is zero it means that either the PWM driver
+	 * does not support initial state retrieval or the PWM has not yet
+	 * been configured.
+	 *
+	 * In either case, we setup the new period and polarity, and assign a
+	 * duty cycle of 0.
+	 */
+	if (!state.period) {
+		state.duty_cycle = 0;
+		state.period = pargs.period;
+		state.polarity = pargs.polarity;
 
-	if (!test_and_set_bit(PWMF_ENABLED, &pwm->flags)) {
-		err = pwm->chip->ops->enable(pwm->chip, pwm);
-		if (err)
-			clear_bit(PWMF_ENABLED, &pwm->flags);
+		return pwm_apply_state(pwm, &state);
 	}
 
-	mutex_unlock(&pwm->lock);
+	/*
+	 * Adjust the PWM duty cycle/period based on the period value provided
+	 * in PWM args.
+	 */
+	if (pargs.period != state.period) {
+		u64 dutycycle = (u64)state.duty_cycle * pargs.period;
 
-	return err;
-}
-EXPORT_SYMBOL_GPL(pwm_enable);
+		do_div(dutycycle, state.period);
+		state.duty_cycle = dutycycle;
+		state.period = pargs.period;
+	}
 
-/**
- * pwm_disable() - stop a PWM output toggling
- * @pwm: PWM device
+	/*
+	 * If the polarity changed, we should also change the duty cycle.
 	 */
-void pwm_disable(struct pwm_device *pwm)
-{
-	if (pwm && test_and_clear_bit(PWMF_ENABLED, &pwm->flags))
-		pwm->chip->ops->disable(pwm->chip, pwm);
+	if (pargs.polarity != state.polarity) {
+		state.polarity = pargs.polarity;
+		state.duty_cycle = state.period - state.duty_cycle;
+	}
+
+	return pwm_apply_state(pwm, &state);
 }
-EXPORT_SYMBOL_GPL(pwm_disable);
+EXPORT_SYMBOL_GPL(pwm_adjust_config);
 
 static struct pwm_chip *of_node_to_pwmchip(struct device_node *np)
 {
@@ -621,13 +669,6 @@ struct pwm_device *of_pwm_get(struct device_node *np, const char *con_id)
 
 	pwm->label = con_id;
 
-	/*
-	 * FIXME: This should be removed once all PWM users properly make use
-	 * of struct pwm_args to initialize the PWM device. As long as this is
-	 * here, the PWM state and hardware state can get out of sync.
-	 */
-	pwm_apply_args(pwm);
-
 put:
 	of_node_put(args.np);
 
@@ -762,13 +803,6 @@ struct pwm_device *pwm_get(struct device *dev, const char *con_id)
 	pwm->args.period = chosen->period;
 	pwm->args.polarity = chosen->polarity;
 
-	/*
-	 * FIXME: This should be removed once all PWM users properly make use
-	 * of struct pwm_args to initialize the PWM device. As long as this is
-	 * here, the PWM state and hardware state can get out of sync.
-	 */
-	pwm_apply_args(pwm);
-
 out:
 	mutex_unlock(&pwm_lookup_lock);
 	return pwm;
@@ -915,15 +949,23 @@ static void pwm_dbg_show(struct pwm_chip *chip, struct seq_file *s)
 
 	for (i = 0; i < chip->npwm; i++) {
 		struct pwm_device *pwm = &chip->pwms[i];
+		struct pwm_state state;
+
+		pwm_get_state(pwm, &state);
 
 		seq_printf(s, " pwm-%-3d (%-20.20s):", i, pwm->label);
 
 		if (test_bit(PWMF_REQUESTED, &pwm->flags))
 			seq_puts(s, " requested");
 
-		if (pwm_is_enabled(pwm))
+		if (state.enabled)
 			seq_puts(s, " enabled");
 
+		seq_printf(s, " period: %u ns", state.period);
+		seq_printf(s, " duty: %u ns", state.duty_cycle);
+		seq_printf(s, " polarity: %s",
+			   state.polarity ? "inverse" : "normal");
+
 		seq_puts(s, "\n");
 	}
 }

drivers/pwm/pwm-crc.c

@@ -75,7 +75,7 @@ static int crc_pwm_config(struct pwm_chip *c, struct pwm_device *pwm,
 		return -EINVAL;
 	}
 
-	if (pwm->period != period_ns) {
+	if (pwm_get_period(pwm) != period_ns) {
 		int clk_div;
 
 		/* changing the clk divisor, need to disable fisrt */

drivers/pwm/pwm-lpc18xx-sct.c

@@ -249,7 +249,7 @@ static int lpc18xx_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
 			   LPC18XX_PWM_EVSTATEMSK(lpc18xx_data->duty_event),
 			   LPC18XX_PWM_EVSTATEMSK_ALL);
 
-	if (pwm->polarity == PWM_POLARITY_NORMAL) {
+	if (pwm_get_polarity(pwm) == PWM_POLARITY_NORMAL) {
 		set_event = lpc18xx_pwm->period_event;
 		clear_event = lpc18xx_data->duty_event;
 		res_action = LPC18XX_PWM_RES_SET;

drivers/pwm/pwm-omap-dmtimer.c

@@ -192,7 +192,7 @@ static int pwm_omap_dmtimer_config(struct pwm_chip *chip,
 		load_value, load_value,	match_value, match_value);
 
 	omap->pdata->set_pwm(omap->dm_timer,
-			      pwm->polarity == PWM_POLARITY_INVERSED,
+			      pwm_get_polarity(pwm) == PWM_POLARITY_INVERSED,
 			      true,
 			      PWM_OMAP_DMTIMER_TRIGGER_OVERFLOW_AND_COMPARE);
 

drivers/pwm/pwm-rcar.c

@@ -157,7 +157,7 @@ static int rcar_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
 		return div;
 
 	/* Let the core driver set pwm->period if disabled and duty_ns == 0 */
-	if (!test_bit(PWMF_ENABLED, &pwm->flags) && !duty_ns)
+	if (!pwm_is_enabled(pwm) && !duty_ns)
 		return 0;
 
 	rcar_pwm_update(rp, RCAR_PWMCR_SYNC, RCAR_PWMCR_SYNC, RCAR_PWMCR);

drivers/pwm/pwm-sun4i.c

@@ -354,7 +354,8 @@ static int sun4i_pwm_probe(struct platform_device *pdev)
 	val = sun4i_pwm_readl(pwm, PWM_CTRL_REG);
 	for (i = 0; i < pwm->chip.npwm; i++)
 		if (!(val & BIT_CH(PWM_ACT_STATE, i)))
-			pwm->chip.pwms[i].polarity = PWM_POLARITY_INVERSED;
+			pwm_set_polarity(&pwm->chip.pwms[i],
+					 PWM_POLARITY_INVERSED);
 	clk_disable_unprepare(pwm->clk);
 
 	return 0;

drivers/pwm/sysfs.c

@@ -26,6 +26,7 @@
 struct pwm_export {
 	struct device child;
 	struct pwm_device *pwm;
+	struct mutex lock;
 };
 
 static struct pwm_export *child_to_pwm_export(struct device *child)
@@ -45,15 +46,20 @@ static ssize_t period_show(struct device *child,
 			   char *buf)
 {
 	const struct pwm_device *pwm = child_to_pwm_device(child);
+	struct pwm_state state;
 
-	return sprintf(buf, "%u\n", pwm_get_period(pwm));
+	pwm_get_state(pwm, &state);
+
+	return sprintf(buf, "%u\n", state.period);
 }
 
 static ssize_t period_store(struct device *child,
 			    struct device_attribute *attr,
 			    const char *buf, size_t size)
 {
-	struct pwm_device *pwm = child_to_pwm_device(child);
+	struct pwm_export *export = child_to_pwm_export(child);
+	struct pwm_device *pwm = export->pwm;
+	struct pwm_state state;
 	unsigned int val;
 	int ret;
 
@@ -61,7 +67,11 @@ static ssize_t period_store(struct device *child,
 	if (ret)
 		return ret;
 
-	ret = pwm_config(pwm, pwm_get_duty_cycle(pwm), val);
+	mutex_lock(&export->lock);
+	pwm_get_state(pwm, &state);
+	state.period = val;
+	ret = pwm_apply_state(pwm, &state);
+	mutex_unlock(&export->lock);
 
 	return ret ? : size;
 }
@@ -71,15 +81,20 @@ static ssize_t duty_cycle_show(struct device *child,
 			       char *buf)
 {
 	const struct pwm_device *pwm = child_to_pwm_device(child);
+	struct pwm_state state;
+
+	pwm_get_state(pwm, &state);
 
-	return sprintf(buf, "%u\n", pwm_get_duty_cycle(pwm));
+	return sprintf(buf, "%u\n", state.duty_cycle);
 }
 
 static ssize_t duty_cycle_store(struct device *child,
 				struct device_attribute *attr,
 				const char *buf, size_t size)
 {
-	struct pwm_device *pwm = child_to_pwm_device(child);
+	struct pwm_export *export = child_to_pwm_export(child);
+	struct pwm_device *pwm = export->pwm;
+	struct pwm_state state;
 	unsigned int val;
 	int ret;
 
@@ -87,7 +102,11 @@ static ssize_t duty_cycle_store(struct device *child,
 	if (ret)
 		return ret;
 
-	ret = pwm_config(pwm, val, pwm_get_period(pwm));
+	mutex_lock(&export->lock);
+	pwm_get_state(pwm, &state);
+	state.duty_cycle = val;
+	ret = pwm_apply_state(pwm, &state);
+	mutex_unlock(&export->lock);
 
 	return ret ? : size;
 }
@@ -97,33 +116,46 @@ static ssize_t enable_show(struct device *child,
 			   char *buf)
 {
 	const struct pwm_device *pwm = child_to_pwm_device(child);
+	struct pwm_state state;
+
+	pwm_get_state(pwm, &state);
 
-	return sprintf(buf, "%d\n", pwm_is_enabled(pwm));
+	return sprintf(buf, "%d\n", state.enabled);
 }
 
 static ssize_t enable_store(struct device *child,
 			    struct device_attribute *attr,
 			    const char *buf, size_t size)
 {
-	struct pwm_device *pwm = child_to_pwm_device(child);
+	struct pwm_export *export = child_to_pwm_export(child);
+	struct pwm_device *pwm = export->pwm;
+	struct pwm_state state;
 	int val, ret;
 
 	ret = kstrtoint(buf, 0, &val);
 	if (ret)
 		return ret;
 
+	mutex_lock(&export->lock);
+
+	pwm_get_state(pwm, &state);
+
 	switch (val) {
 	case 0:
-		pwm_disable(pwm);
+		state.enabled = false;
 		break;
 	case 1:
-		ret = pwm_enable(pwm);
+		state.enabled = true;
 		break;
 	default:
 		ret = -EINVAL;
-		break;
+		goto unlock;
 	}
 
+	pwm_apply_state(pwm, &state);
+
+unlock:
+	mutex_unlock(&export->lock);
 	return ret ? : size;
 }
 
@@ -133,8 +165,11 @@ static ssize_t polarity_show(struct device *child,
 {
 	const struct pwm_device *pwm = child_to_pwm_device(child);
 	const char *polarity = "unknown";
+	struct pwm_state state;
+
+	pwm_get_state(pwm, &state);
 
-	switch (pwm_get_polarity(pwm)) {
+	switch (state.polarity) {
 	case PWM_POLARITY_NORMAL:
 		polarity = "normal";
 		break;
@@ -151,8 +186,10 @@ static ssize_t polarity_store(struct device *child,
 			      struct device_attribute *attr,
 			      const char *buf, size_t size)
 {
-	struct pwm_device *pwm = child_to_pwm_device(child);
+	struct pwm_export *export = child_to_pwm_export(child);
+	struct pwm_device *pwm = export->pwm;
 	enum pwm_polarity polarity;
+	struct pwm_state state;
 	int ret;
 
 	if (sysfs_streq(buf, "normal"))
@@ -162,7 +199,11 @@ static ssize_t polarity_store(struct device *child,
 	else
 		return -EINVAL;
 
-	ret = pwm_set_polarity(pwm, polarity);
+	mutex_lock(&export->lock);
+	pwm_get_state(pwm, &state);
+	state.polarity = polarity;
+	ret = pwm_apply_state(pwm, &state);
+	mutex_unlock(&export->lock);
 
 	return ret ? : size;
 }
@@ -203,6 +244,7 @@ static int pwm_export_child(struct device *parent, struct pwm_device *pwm)
 	}
 
 	export->pwm = pwm;
+	mutex_init(&export->lock);
 
 	export->child.release = pwm_export_release;
 	export->child.parent = parent;

drivers/video/backlight/lm3630a_bl.c

@@ -162,7 +162,7 @@ static int lm3630a_intr_config(struct lm3630a_chip *pchip)
 
 static void lm3630a_pwm_ctrl(struct lm3630a_chip *pchip, int br, int br_max)
 {
-	unsigned int period = pwm_get_period(pchip->pwmd);
+	unsigned int period = pchip->pdata->pwm_period;
 	unsigned int duty = br * period / br_max;
 
 	pwm_config(pchip->pwmd, duty, period);
@@ -424,8 +424,13 @@ static int lm3630a_probe(struct i2c_client *client,
 			dev_err(&client->dev, "fail : get pwm device\n");
 			return PTR_ERR(pchip->pwmd);
 		}
+
+		/*
+		 * FIXME: pwm_apply_args() should be removed when switching to
+		 * the atomic PWM API.
+		 */
+		pwm_apply_args(pchip->pwmd);
 	}
-	pchip->pwmd->period = pdata->pwm_period;
 
 	/* interrupt enable  : irq 0 is not allowed */
 	pchip->irq = client->irq;

drivers/video/backlight/lp855x_bl.c

@@ -246,6 +246,12 @@ static void lp855x_pwm_ctrl(struct lp855x *lp, int br, int max_br)
 			return;
 
 		lp->pwm = pwm;
+
+		/*
+		 * FIXME: pwm_apply_args() should be removed when switching to
+		 * the atomic PWM API.
+		 */
+		pwm_apply_args(pwm);
 	}
 
 	pwm_config(lp->pwm, duty, period);

drivers/video/backlight/lp8788_bl.c

@@ -145,6 +145,12 @@ static void lp8788_pwm_ctrl(struct lp8788_bl *bl, int br, int max_br)
 		}
 
 		bl->pwm = pwm;
+
+		/*
+		 * FIXME: pwm_apply_args() should be removed when switching to
+		 * the atomic PWM API.
+		 */
+		pwm_apply_args(pwm);
 	}
 
 	pwm_config(bl->pwm, duty, period);

drivers/video/backlight/pwm_bl.c

@@ -201,6 +201,7 @@ static int pwm_backlight_probe(struct platform_device *pdev)
 	struct device_node *node = pdev->dev.of_node;
 	struct pwm_bl_data *pb;
 	int initial_blank = FB_BLANK_UNBLANK;
+	struct pwm_args pargs;
 	int ret;
 
 	if (!data) {
@@ -306,17 +307,22 @@ static int pwm_backlight_probe(struct platform_device *pdev)
 
 	dev_dbg(&pdev->dev, "got pwm for backlight\n");
 
+	/*
+	 * FIXME: pwm_apply_args() should be removed when switching to
+	 * the atomic PWM API.
+	 */
+	pwm_apply_args(pb->pwm);
+
 	/*
 	 * The DT case will set the pwm_period_ns field to 0 and store the
 	 * period, parsed from the DT, in the PWM device. For the non-DT case,
 	 * set the period from platform data if it has not already been set
 	 * via the PWM lookup table.
 	 */
-	pb->period = pwm_get_period(pb->pwm);
-	if (!pb->period && (data->pwm_period_ns > 0)) {
+	pwm_get_args(pb->pwm, &pargs);
+	pb->period = pargs.period;
+	if (!pb->period && (data->pwm_period_ns > 0))
 		pb->period = data->pwm_period_ns;
-		pwm_set_period(pb->pwm, data->pwm_period_ns);
-	}
 
 	pb->lth_brightness = data->lth_brightness * (pb->period / pb->scale);
 

drivers/video/fbdev/ssd1307fb.c

@@ -286,6 +286,7 @@ static int ssd1307fb_init(struct ssd1307fb_par *par)
 {
 	int ret;
 	u32 precharge, dclk, com_invdir, compins;
+	struct pwm_args pargs;
 
 	if (par->device_info->need_pwm) {
 		par->pwm = pwm_get(&par->client->dev, NULL);
@@ -294,7 +295,15 @@ static int ssd1307fb_init(struct ssd1307fb_par *par)
 			return PTR_ERR(par->pwm);
 		}
 
-		par->pwm_period = pwm_get_period(par->pwm);
+		/*
+		 * FIXME: pwm_apply_args() should be removed when switching to
+		 * the atomic PWM API.
+		 */
+		pwm_apply_args(par->pwm);
+
+		pwm_get_args(par->pwm, &pargs);
+
+		par->pwm_period = pargs.period;
 		/* Enable the PWM */
 		pwm_config(par->pwm, par->pwm_period / 2, par->pwm_period);
 		pwm_enable(par->pwm);

include/linux/pwm.h

@@ -5,59 +5,7 @@
 #include <linux/mutex.h>
 #include <linux/of.h>
 
-struct pwm_device;
 struct seq_file;
-
-#if IS_ENABLED(CONFIG_PWM)
-/*
- * pwm_request - request a PWM device
- */
-struct pwm_device *pwm_request(int pwm_id, const char *label);
-
-/*
- * pwm_free - free a PWM device
- */
-void pwm_free(struct pwm_device *pwm);
-
-/*
- * pwm_config - change a PWM device configuration
- */
-int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns);
-
-/*
- * pwm_enable - start a PWM output toggling
- */
-int pwm_enable(struct pwm_device *pwm);
-
-/*
- * pwm_disable - stop a PWM output toggling
- */
-void pwm_disable(struct pwm_device *pwm);
-#else
-static inline struct pwm_device *pwm_request(int pwm_id, const char *label)
-{
-	return ERR_PTR(-ENODEV);
-}
-
-static inline void pwm_free(struct pwm_device *pwm)
-{
-}
-
-static inline int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)
-{
-	return -EINVAL;
-}
-
-static inline int pwm_enable(struct pwm_device *pwm)
-{
-	return -EINVAL;
-}
-
-static inline void pwm_disable(struct pwm_device *pwm)
-{
-}
-#endif
-
 struct pwm_chip;
 
 /**
@@ -94,8 +42,21 @@ struct pwm_args {
 
 enum {
 	PWMF_REQUESTED = 1 << 0,
-	PWMF_ENABLED = 1 << 1,
-	PWMF_EXPORTED = 1 << 2,
+	PWMF_EXPORTED = 1 << 1,
+};
+
+/*
+ * struct pwm_state - state of a PWM channel
+ * @period: PWM period (in nanoseconds)
+ * @duty_cycle: PWM duty cycle (in nanoseconds)
+ * @polarity: PWM polarity
+ * @enabled: PWM enabled status
+ */
+struct pwm_state {
+	unsigned int period;
+	unsigned int duty_cycle;
+	enum pwm_polarity polarity;
+	bool enabled;
 };
 
 /**
@@ -106,11 +67,8 @@ enum {
  * @pwm: global index of the PWM device
  * @chip: PWM chip providing this PWM device
  * @chip_data: chip-private data associated with the PWM device
- * @lock: used to serialize accesses to the PWM device where necessary
- * @period: period of the PWM signal (in nanoseconds)
- * @duty_cycle: duty cycle of the PWM signal (in nanoseconds)
- * @polarity: polarity of the PWM signal
  * @args: PWM arguments
+ * @state: curent PWM channel state
  */
 struct pwm_device {
 	const char *label;
@@ -119,50 +77,68 @@ struct pwm_device {
 	unsigned int pwm;
 	struct pwm_chip *chip;
 	void *chip_data;
-	struct mutex lock;
-
-	unsigned int period;
-	unsigned int duty_cycle;
-	enum pwm_polarity polarity;
 
 	struct pwm_args args;
+	struct pwm_state state;
 };
 
+/**
+ * pwm_get_state() - retrieve the current PWM state
+ * @pwm: PWM device
+ * @state: state to fill with the current PWM state
+ */
+static inline void pwm_get_state(const struct pwm_device *pwm,
+				 struct pwm_state *state)
+{
+	*state = pwm->state;
+}
+
 static inline bool pwm_is_enabled(const struct pwm_device *pwm)
 {
-	return test_bit(PWMF_ENABLED, &pwm->flags);
+	struct pwm_state state;
+
+	pwm_get_state(pwm, &state);
+
+	return state.enabled;
 }
 
 static inline void pwm_set_period(struct pwm_device *pwm, unsigned int period)
 {
 	if (pwm)
-		pwm->period = period;
+		pwm->state.period = period;
 }
 
 static inline unsigned int pwm_get_period(const struct pwm_device *pwm)
 {
-	return pwm ? pwm->period : 0;
+	struct pwm_state state;
+
+	pwm_get_state(pwm, &state);
+
+	return state.period;
 }
 
 static inline void pwm_set_duty_cycle(struct pwm_device *pwm, unsigned int duty)
 {
 	if (pwm)
-		pwm->duty_cycle = duty;
+		pwm->state.duty_cycle = duty;
 }
 
 static inline unsigned int pwm_get_duty_cycle(const struct pwm_device *pwm)
 {
-	return pwm ? pwm->duty_cycle : 0;
-}
+	struct pwm_state state;
 
-/*
- * pwm_set_polarity - configure the polarity of a PWM signal
- */
-int pwm_set_polarity(struct pwm_device *pwm, enum pwm_polarity polarity);
+	pwm_get_state(pwm, &state);
+
+	return state.duty_cycle;
+}
 
 static inline enum pwm_polarity pwm_get_polarity(const struct pwm_device *pwm)
 {
-	return pwm ? pwm->polarity : PWM_POLARITY_NORMAL;
+	struct pwm_state state;
+
+	pwm_get_state(pwm, &state);
+
+	return state.polarity;
 }
 
 static inline void pwm_get_args(const struct pwm_device *pwm,
@@ -171,12 +147,6 @@ static inline void pwm_get_args(const struct pwm_device *pwm,
 	*args = pwm->args;
 }
 
-static inline void pwm_apply_args(struct pwm_device *pwm)
-{
-	pwm_set_period(pwm, pwm->args.period);
-	pwm_set_polarity(pwm, pwm->args.polarity);
-}
-
 /**
  * struct pwm_ops - PWM controller operations
  * @request: optional hook for requesting a PWM
@@ -185,6 +155,13 @@ static inline void pwm_apply_args(struct pwm_device *pwm)
  * @set_polarity: configure the polarity of this PWM
  * @enable: enable PWM output toggling
  * @disable: disable PWM output toggling
+ * @apply: atomically apply a new PWM config. The state argument
+ *	   should be adjusted with the real hardware config (if the
+ *	   approximate the period or duty_cycle value, state should
+ *	   reflect it)
+ * @get_state: get the current PWM state. This function is only
+ *	       called once per PWM device when the PWM chip is
+ *	       registered.
  * @dbg_show: optional routine to show contents in debugfs
  * @owner: helps prevent removal of modules exporting active PWMs
  */
@@ -197,6 +174,10 @@ struct pwm_ops {
 			    enum pwm_polarity polarity);
 	int (*enable)(struct pwm_chip *chip, struct pwm_device *pwm);
 	void (*disable)(struct pwm_chip *chip, struct pwm_device *pwm);
+	int (*apply)(struct pwm_chip *chip, struct pwm_device *pwm,
+		     struct pwm_state *state);
+	void (*get_state)(struct pwm_chip *chip, struct pwm_device *pwm,
+			  struct pwm_state *state);
 #ifdef CONFIG_DEBUG_FS
 	void (*dbg_show)(struct pwm_chip *chip, struct seq_file *s);
 #endif
@@ -232,6 +213,115 @@ struct pwm_chip {
 };
 
 #if IS_ENABLED(CONFIG_PWM)
+/* PWM user APIs */
+struct pwm_device *pwm_request(int pwm_id, const char *label);
+void pwm_free(struct pwm_device *pwm);
+int pwm_apply_state(struct pwm_device *pwm, struct pwm_state *state);
+int pwm_adjust_config(struct pwm_device *pwm);
+
+/**
+ * pwm_config() - change a PWM device configuration
+ * @pwm: PWM device
+ * @duty_ns: "on" time (in nanoseconds)
+ * @period_ns: duration (in nanoseconds) of one cycle
+ *
+ * Returns: 0 on success or a negative error code on failure.
+ */
+static inline int pwm_config(struct pwm_device *pwm, int duty_ns,
+			     int period_ns)
+{
+	struct pwm_state state;
+
+	if (!pwm)
+		return -EINVAL;
+
+	pwm_get_state(pwm, &state);
+	if (state.duty_cycle == duty_ns && state.period == period_ns)
+		return 0;
+
+	state.duty_cycle = duty_ns;
+	state.period = period_ns;
+	return pwm_apply_state(pwm, &state);
+}
+
+/**
+ * pwm_set_polarity() - configure the polarity of a PWM signal
+ * @pwm: PWM device
+ * @polarity: new polarity of the PWM signal
+ *
+ * Note that the polarity cannot be configured while the PWM device is
+ * enabled.
+ *
+ * Returns: 0 on success or a negative error code on failure.
+ */
+static inline int pwm_set_polarity(struct pwm_device *pwm,
+				   enum pwm_polarity polarity)
+{
+	struct pwm_state state;
+
+	if (!pwm)
+		return -EINVAL;
+
+	pwm_get_state(pwm, &state);
+	if (state.polarity == polarity)
+		return 0;
+
+	/*
+	 * Changing the polarity of a running PWM without adjusting the
+	 * dutycycle/period value is a bit risky (can introduce glitches).
+	 * Return -EBUSY in this case.
+	 * Note that this is allowed when using pwm_apply_state() because
+	 * the user specifies all the parameters.
+	 */
+	if (state.enabled)
+		return -EBUSY;
+
+	state.polarity = polarity;
+	return pwm_apply_state(pwm, &state);
+}
+
+/**
+ * pwm_enable() - start a PWM output toggling
+ * @pwm: PWM device
+ *
+ * Returns: 0 on success or a negative error code on failure.
+ */
+static inline int pwm_enable(struct pwm_device *pwm)
+{
+	struct pwm_state state;
+
+	if (!pwm)
+		return -EINVAL;
+
+	pwm_get_state(pwm, &state);
+	if (state.enabled)
+		return 0;
+
+	state.enabled = true;
+	return pwm_apply_state(pwm, &state);
+}
+
+/**
+ * pwm_disable() - stop a PWM output toggling
+ * @pwm: PWM device
+ */
+static inline void pwm_disable(struct pwm_device *pwm)
+{
+	struct pwm_state state;
+
+	if (!pwm)
+		return;
+
+	pwm_get_state(pwm, &state);
+	if (!state.enabled)
+		return;
+
+	state.enabled = false;
+	pwm_apply_state(pwm, &state);
+}
+
+
+/* PWM provider APIs */
 int pwm_set_chip_data(struct pwm_device *pwm, void *data);
 void *pwm_get_chip_data(struct pwm_device *pwm);
 
@@ -257,6 +347,47 @@ void devm_pwm_put(struct device *dev, struct pwm_device *pwm);
 
 bool pwm_can_sleep(struct pwm_device *pwm);
 #else
+static inline struct pwm_device *pwm_request(int pwm_id, const char *label)
+{
+	return ERR_PTR(-ENODEV);
+}
+
+static inline void pwm_free(struct pwm_device *pwm)
+{
+}
+
+static inline int pwm_apply_state(struct pwm_device *pwm,
+				  const struct pwm_state *state)
+{
+	return -ENOTSUPP;
+}
+
+static inline int pwm_adjust_config(struct pwm_device *pwm)
+{
+	return -ENOTSUPP;
+}
+
+static inline int pwm_config(struct pwm_device *pwm, int duty_ns,
+			     int period_ns)
+{
+	return -EINVAL;
+}
+
+static inline int pwm_set_polarity(struct pwm_device *pwm,
+				   enum pwm_polarity polarity)
+{
+	return -ENOTSUPP;
+}
+
+static inline int pwm_enable(struct pwm_device *pwm)
+{
+	return -EINVAL;
+}
+
+static inline void pwm_disable(struct pwm_device *pwm)
+{
+}
+
 static inline int pwm_set_chip_data(struct pwm_device *pwm, void *data)
 {
 	return -EINVAL;
@@ -328,6 +459,34 @@ static inline bool pwm_can_sleep(struct pwm_device *pwm)
 }
 #endif
 
+static inline void pwm_apply_args(struct pwm_device *pwm)
+{
+	/*
+	 * PWM users calling pwm_apply_args() expect to have a fresh config
+	 * where the polarity and period are set according to pwm_args info.
+	 * The problem is, polarity can only be changed when the PWM is
+	 * disabled.
+	 *
+	 * PWM drivers supporting hardware readout may declare the PWM device
+	 * as enabled, and prevent polarity setting, which changes from the
+	 * existing behavior, where all PWM devices are declared as disabled
+	 * at startup (even if they are actually enabled), thus authorizing
+	 * polarity setting.
+	 *
+	 * Instead of setting ->enabled to false, we call pwm_disable()
+	 * before pwm_set_polarity() to ensure that everything is configured
+	 * as expected, and the PWM is really disabled when the user request
+	 * it.
+	 *
+	 * Note that PWM users requiring a smooth handover between the
+	 * bootloader and the kernel (like critical regulators controlled by
+	 * PWM devices) will have to switch to the atomic API and avoid calling
+	 * pwm_apply_args().
+	 */
+	pwm_disable(pwm);
+	pwm_set_polarity(pwm, pwm->args.polarity);
+}
+
 struct pwm_lookup {
 	struct list_head list;
 	const char *provider;