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[PATCH v5 00/24] pwm: add support for atomic update

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  [PATCH v5 00/24] pwm: add support for atomic update Boris Brezillon <boris.brezillon@free-electrons.com> - 2016-04-14 21:30 +0200
    [PATCH v5 02/24] pwm: use pwm_get/set_xxx() helpers where appropriate Boris Brezillon <boris.brezillon@free-electrons.com> - 2016-04-14 21:30 +0200
      Re: [PATCH v5 02/24] pwm: use pwm_get/set_xxx() helpers where appropriate Joachim Eastwood <manabian@gmail.com> - 2016-04-14 21:30 +0200
    [PATCH v5 05/24] input: misc: max77693: use pwm_get_args() where appropriate Boris Brezillon <boris.brezillon@free-electrons.com> - 2016-04-14 21:30 +0200
    [PATCH v5 18/24] pwm: introduce the pwm_state concept Boris Brezillon <boris.brezillon@free-electrons.com> - 2016-04-14 21:30 +0200
    [PATCH v5 08/24] fbdev: ssd1307fb: use pwm_get_args() where appropriate Boris Brezillon <boris.brezillon@free-electrons.com> - 2016-04-14 21:30 +0200
    [PATCH v5 16/24] ARM: explicitly apply PWM config extracted from pwm_args Boris Brezillon <boris.brezillon@free-electrons.com> - 2016-04-14 21:30 +0200
      Re: [PATCH v5 16/24] ARM: explicitly apply PWM config extracted from  pwm_args Krzysztof Kozlowski <k.kozlowski@samsung.com> - 2016-04-15 10:20 +0200
    [PATCH v5 15/24] drm: i915: explicitly apply PWM config extracted from pwm_args Boris Brezillon <boris.brezillon@free-electrons.com> - 2016-04-14 21:30 +0200
    [PATCH v5 03/24] clk: pwm: use pwm_get_args() where appropriate Boris Brezillon <boris.brezillon@free-electrons.com> - 2016-04-14 21:30 +0200
    [PATCH v5 17/24] pwm: keep PWM state in sync with hardware state Boris Brezillon <boris.brezillon@free-electrons.com> - 2016-04-14 21:30 +0200
    [PATCH v5 20/24] pwm: add the PWM initial state retrieval infra Boris Brezillon <boris.brezillon@free-electrons.com> - 2016-04-14 21:30 +0200
    [PATCH v5 21/24] pwm: add the core infrastructure to allow atomic update Boris Brezillon <boris.brezillon@free-electrons.com> - 2016-04-14 21:30 +0200

#1379245 — [PATCH v5 00/24] pwm: add support for atomic update

Hello,

This series adds support for atomic PWM update, or IOW, the capability
to update all the parameters of a PWM device (enabled/disabled, period,
duty and polarity) in one go.

It also adds support for initial PWM state retrieval (or hardware
readout), which should allow smooth handover between the bootloader and
Linux. For example, critical PWM users (like critical regulators
controlled by a PWM) can query the current PWM state, and adapt the PWM
config without having to disable/enable the PWM, or abruptly change the
period/dutycyle/polarity config.

In this version, I dropped all patches converting PWM users and PWM
drivers to the atomic API in order to limit the number of patches and
ease review. I plan to send the remaining patches once these ones have
been accepted.

If you want to test the series, or see the big picture, you can have a
look at this branch [1].

Best Regards,

Boris

[1]https://github.com/bbrezillon/linux-rk/tree/atomic-pwm

Changes since v5:
- fix bugs in pwm_apply_state() implementation
- drop already applied patches
- s/pstate/state/
- add pwm_apply_args() helper
- limit the series to core changes and required changes in PWM users code

Changes since v4:
- introduce pwm_args to expose per-board/platform config
- deprecate non-atomic APIs
- implement non-atomic functions as wrappers around atomic ones
- patch all PWM users to use the atomic API
- rename the ->reset_state() hook into ->get_state()
- drop most acks
- rework PWM config in the pwm-regulator driver
- patch sun4i and sti PWM drivers to support HW readout

Changes since v3:
- rebased on pwm/for-next after pulling 4.4-rc1
- replace direct access to pwm fields by pwm_get/set_xxx() helpers, thus
  fixing some build errors
- split changes to allow each maintainer to review/ack or take the
  modification through its subsystem

Changes since v2:
- rebased on top of 4.3-rc2
- reintroduced pwm-regulator patches

Changes since v1:
- dropped applied patches
- squashed Heiko's fixes into the rockchip driver changes
- made a few cosmetic changes
- added kerneldoc comments
- added Heiko's patch to display more information in debugfs
- dropped pwm-regulator patches (should be submitted separately)

Boris Brezillon (23):
  pwm: introduce the pwm_args concept
  pwm: use pwm_get/set_xxx() helpers where appropriate
  clk: pwm: use pwm_get_args() where appropriate
  hwmon: pwm-fan: use pwm_get_args() where appropriate
  input: misc: max77693: use pwm_get_args() where appropriate
  leds: pwm: use pwm_get_args() where appropriate
  regulator: pwm: use pwm_get_args() where appropriate
  fbdev: ssd1307fb: use pwm_get_args() where appropriate
  backlight: pwm_bl: use pwm_get_args() where appropriate
  backlight: lp8788: explicitly apply PWM config extracted from pwm_args
  backlight: lp855x: explicitly apply PWM config extracted from pwm_args
  backlight: lm3630a: explicitly apply PWM config extracted from
    pwm_args
  input: misc: max8997: explicitly apply PWM config extracted from
    pwm_args
  input: misc: pwm-beeper: explicitly apply PWM config extracted from
    pwm_args
  drm: i915: explicitly apply PWM config extracted from pwm_args
  ARM: explicitly apply PWM config extracted from pwm_args
  pwm: keep PWM state in sync with hardware state
  pwm: introduce the pwm_state concept
  pwm: move the enabled/disabled info into pwm_state
  pwm: add the PWM initial state retrieval infra
  pwm: add the core infrastructure to allow atomic update
  pwm: update documentation
  pwm: switch to the atomic API

Heiko Stübner (1):
  pwm: add information about polarity, duty cycle and period to debugfs

 Documentation/pwm.txt                |  30 +++-
 arch/arm/mach-s3c24xx/mach-rx1950.c  |   6 +
 drivers/clk/clk-pwm.c                |  17 +-
 drivers/gpu/drm/i915/intel_panel.c   |   6 +
 drivers/hwmon/pwm-fan.c              |  26 ++-
 drivers/input/misc/max77693-haptic.c |  17 +-
 drivers/input/misc/max8997_haptic.c  |   6 +
 drivers/input/misc/pwm-beeper.c      |   6 +
 drivers/leds/leds-pwm.c              |  11 +-
 drivers/pwm/core.c                   | 214 ++++++++++++++--------
 drivers/pwm/pwm-clps711x.c           |   2 +-
 drivers/pwm/pwm-crc.c                |   2 +-
 drivers/pwm/pwm-lpc18xx-sct.c        |   2 +-
 drivers/pwm/pwm-omap-dmtimer.c       |   2 +-
 drivers/pwm/pwm-pxa.c                |   2 +-
 drivers/pwm/pwm-sun4i.c              |   3 +-
 drivers/pwm/sysfs.c                  |  61 ++++---
 drivers/regulator/pwm-regulator.c    |  20 ++-
 drivers/video/backlight/lm3630a_bl.c |   6 +
 drivers/video/backlight/lp855x_bl.c  |   6 +
 drivers/video/backlight/lp8788_bl.c  |   6 +
 drivers/video/backlight/pwm_bl.c     |  10 +-
 drivers/video/fbdev/ssd1307fb.c      |  11 +-
 include/linux/pwm.h                  | 335 +++++++++++++++++++++++++++--------
 24 files changed, 606 insertions(+), 201 deletions(-)

-- 
2.5.0

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#1379246 — [PATCH v5 02/24] pwm: use pwm_get/set_xxx() helpers where appropriate

Use pwm_get/set_xxx() helpers instead of directly accessing the pwm->xxx
field. Doing that will ease adaptation of the PWM framework to support
atomic update.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
---
Patch generated with the following coccinelle script:

--->8---
virtual patch

@@
struct pwm_device *p;
expression e;
@@
(
-(p)->polarity = e;
+pwm_set_polarity(p, e);
|
-(p)->polarity
+pwm_get_polarity(p)
|
-(p)->period = e;
+pwm_set_period(p, e);
|
-(p)->period
+pwm_get_period(p)
|
-(p)->duty_cycle = e;
+pwm_set_duty_cycle(p, e);
|
-(p)->duty_cycle
+pwm_get_duty_cycle(p)
)
--->8---
---
 drivers/pwm/pwm-crc.c          | 2 +-
 drivers/pwm/pwm-lpc18xx-sct.c  | 2 +-
 drivers/pwm/pwm-omap-dmtimer.c | 2 +-
 drivers/pwm/pwm-sun4i.c        | 3 ++-
 4 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/pwm/pwm-crc.c b/drivers/pwm/pwm-crc.c
index 7101c70..bd0ebd0 100644
--- a/drivers/pwm/pwm-crc.c
+++ b/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 */
diff --git a/drivers/pwm/pwm-lpc18xx-sct.c b/drivers/pwm/pwm-lpc18xx-sct.c
index 9861fed..19dc64c 100644
--- a/drivers/pwm/pwm-lpc18xx-sct.c
+++ b/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;
diff --git a/drivers/pwm/pwm-omap-dmtimer.c b/drivers/pwm/pwm-omap-dmtimer.c
index b7e6ecb..3e95090 100644
--- a/drivers/pwm/pwm-omap-dmtimer.c
+++ b/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);
 
diff --git a/drivers/pwm/pwm-sun4i.c b/drivers/pwm/pwm-sun4i.c
index 67af9f6..03a99a5 100644
--- a/drivers/pwm/pwm-sun4i.c
+++ b/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;
-- 
2.5.0

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#1379258 — Re: [PATCH v5 02/24] pwm: use pwm_get/set_xxx() helpers where appropriate

On 14 April 2016 at 21:17, Boris Brezillon
<boris.brezillon@free-electrons.com> wrote:
> Use pwm_get/set_xxx() helpers instead of directly accessing the pwm->xxx
> field. Doing that will ease adaptation of the PWM framework to support
> atomic update.
>
> Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
> ---
> Patch generated with the following coccinelle script:
>
> --->8---
> virtual patch
>
> @@
> struct pwm_device *p;
> expression e;
> @@
> (
> -(p)->polarity = e;
> +pwm_set_polarity(p, e);
> |
> -(p)->polarity
> +pwm_get_polarity(p)
> |
> -(p)->period = e;
> +pwm_set_period(p, e);
> |
> -(p)->period
> +pwm_get_period(p)
> |
> -(p)->duty_cycle = e;
> +pwm_set_duty_cycle(p, e);
> |
> -(p)->duty_cycle
> +pwm_get_duty_cycle(p)
> )
> --->8---
> ---
>  drivers/pwm/pwm-crc.c          | 2 +-
>  drivers/pwm/pwm-lpc18xx-sct.c  | 2 +-

> diff --git a/drivers/pwm/pwm-lpc18xx-sct.c b/drivers/pwm/pwm-lpc18xx-sct.c
> index 9861fed..19dc64c 100644
> --- a/drivers/pwm/pwm-lpc18xx-sct.c
> +++ b/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;

For the lpc18xx-sct part:
Acked-by: Joachim Eastwood <manabian@gmail.com>


regards,
Joachim Eastwood

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#1379247 — [PATCH v5 05/24] input: misc: max77693: use pwm_get_args() where appropriate

The PWM framework has clarified the concept of reference PWM config
(the platform dependent config retrieved from the DT or the PWM
lookup table) and real PWM state.

Use pwm_get_args() when the PWM user wants to retrieve this reference
config and not the current state.

This is part of the rework allowing the PWM framework to support
hardware readout and expose real PWM state even when the PWM has
just been requested (before the user calls pwm_config/enable/disable()).

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
---
 drivers/input/misc/max77693-haptic.c | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/drivers/input/misc/max77693-haptic.c b/drivers/input/misc/max77693-haptic.c
index 6d96bff..29ddeb7 100644
--- a/drivers/input/misc/max77693-haptic.c
+++ b/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");
-- 
2.5.0

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#1379249 — [PATCH v5 18/24] pwm: introduce the pwm_state concept

The PWM state, represented by its period, duty_cycle and polarity,
is currently directly stored in the PWM device.
Declare a pwm_state structure embedding those field so that we can later
use this struct to atomically update all the PWM parameters at once.

All pwm_get_xxx() helpers are now implemented as wrappers around
pwm_get_state().

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
---
 drivers/pwm/core.c  |  8 ++++----
 include/linux/pwm.h | 54 +++++++++++++++++++++++++++++++++++++++++------------
 2 files changed, 46 insertions(+), 16 deletions(-)

diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 26c3cf5..59bcece 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -268,7 +268,7 @@ int pwmchip_add_with_polarity(struct pwm_chip *chip,
 		pwm->chip = chip;
 		pwm->pwm = chip->base + i;
 		pwm->hwpwm = i;
-		pwm->polarity = polarity;
+		pwm->state.polarity = polarity;
 
 		radix_tree_insert(&pwm_tree, pwm->pwm, pwm);
 	}
@@ -446,8 +446,8 @@ int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns)
 	if (err)
 		return err;
 
-	pwm->duty_cycle = duty_ns;
-	pwm->period = period_ns;
+	pwm->state.duty_cycle = duty_ns;
+	pwm->state.period = period_ns;
 
 	return 0;
 }
@@ -480,7 +480,7 @@ int pwm_set_polarity(struct pwm_device *pwm, enum pwm_polarity polarity)
 	if (err)
 		return err;
 
-	pwm->polarity = polarity;
+	pwm->state.polarity = polarity;
 
 	return 0;
 }
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index 2f500a5..3022c05 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -97,6 +97,18 @@ enum {
 	PWMF_EXPORTED = 1 << 2,
 };
 
+/*
+ * struct pwm_state - state of a PWM channel
+ * @period: PWM period (in nanoseconds)
+ * @duty_cycle: PWM duty cycle (in nanoseconds)
+ * @polarity: PWM polarity
+ */
+struct pwm_state {
+	unsigned int period;
+	unsigned int duty_cycle;
+	enum pwm_polarity polarity;
+};
+
 /**
  * struct pwm_device - PWM channel object
  * @label: name of the PWM device
@@ -105,10 +117,8 @@ 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
- * @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;
@@ -118,13 +128,21 @@ struct pwm_device {
 	struct pwm_chip *chip;
 	void *chip_data;
 
-	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);
@@ -133,23 +151,31 @@ static inline bool pwm_is_enabled(const struct pwm_device *pwm)
 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_get_state(pwm, &state);
+
+	return state.duty_cycle;
 }
 
 /*
@@ -159,7 +185,11 @@ int pwm_set_polarity(struct pwm_device *pwm, enum pwm_polarity polarity);
 
 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,
-- 
2.5.0

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#1379250 — [PATCH v5 08/24] fbdev: ssd1307fb: use pwm_get_args() where appropriate

The PWM framework has clarified the concept of reference PWM config
(the platform dependent config retrieved from the DT or the PWM
lookup table) and real PWM state.

Use pwm_get_args() when the PWM user wants to retrieve this reference
config and not the current state.

This is part of the rework allowing the PWM framework to support
hardware readout and expose real PWM state even when the PWM has
just been requested (before the user calls pwm_config/enable/disable()).

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
---
 drivers/video/fbdev/ssd1307fb.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/ssd1307fb.c b/drivers/video/fbdev/ssd1307fb.c
index fa34808..652f688 100644
--- a/drivers/video/fbdev/ssd1307fb.c
+++ b/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);
-- 
2.5.0

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#1379253 — [PATCH v5 16/24] ARM: explicitly apply PWM config extracted from pwm_args

Call pwm_apply_args() just after requesting the PWM device so that the
polarity and period are initialized according to the information provided
in pwm_args.

This is an intermediate state, and pwm_apply_args() should be dropped as
soon as the atomic PWM infrastructure is in place and the driver makes
use of it.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
---
 arch/arm/mach-s3c24xx/mach-rx1950.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/arm/mach-s3c24xx/mach-rx1950.c b/arch/arm/mach-s3c24xx/mach-rx1950.c
index 774c982..25a139b 100644
--- a/arch/arm/mach-s3c24xx/mach-rx1950.c
+++ b/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);
 
-- 
2.5.0

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#1379536 — Re: [PATCH v5 16/24] ARM: explicitly apply PWM config extracted from pwm_args

On 04/14/2016 09:17 PM, Boris Brezillon wrote:
> Call pwm_apply_args() just after requesting the PWM device so that the
> polarity and period are initialized according to the information provided
> in pwm_args.
> 
> This is an intermediate state, and pwm_apply_args() should be dropped as
> soon as the atomic PWM infrastructure is in place and the driver makes
> use of it.
> 
> Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
> ---
>  arch/arm/mach-s3c24xx/mach-rx1950.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 

Acked-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>

Best regards,
Krzysztof

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#1379255 — [PATCH v5 15/24] drm: i915: explicitly apply PWM config extracted from pwm_args

Call pwm_apply_args() just after requesting the PWM device so that the
polarity and period are initialized according to the information provided
in pwm_args.

This is an intermediate state, and pwm_apply_args() should be dropped as
soon as the atomic PWM infrastructure is in place and the driver makes
use of it.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
---
 drivers/gpu/drm/i915/intel_panel.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
index 21ee647..dc3a2e4 100644
--- a/drivers/gpu/drm/i915/intel_panel.c
+++ b/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) {
-- 
2.5.0

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#1379256 — [PATCH v5 03/24] clk: pwm: use pwm_get_args() where appropriate

The PWM framework has clarified the concept of reference PWM config
(the platform dependent config retrieved from the DT or the PWM
lookup table) and real PWM state.

Use pwm_get_args() when the PWM user wants to retrieve this reference
config and not the current state.

This is part of the rework allowing the PWM framework to support
hardware readout and expose real PWM state even when the PWM has
just been requested (before the user calls pwm_config/enable/disable()).

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Acked-by: Stephen Boyd <sboyd@codeaurora.org>
---
 drivers/clk/clk-pwm.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/drivers/clk/clk-pwm.c b/drivers/clk/clk-pwm.c
index 8830458..1630a1f 100644
--- a/drivers/clk/clk-pwm.c
+++ b/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;
 
-- 
2.5.0

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#1379257 — [PATCH v5 17/24] pwm: keep PWM state in sync with hardware state

Before the introduction of pwm_args, the core was resetting the PWM period
and polarity states to the reference values (those provided through the
DT, a PWM lookup table or hardcoded in the driver).

Now that all PWM users are correctly using pwm_args to configure their
PWM device, we can safely remove the pwm_apply_args() call in
pwm_device_request().

We can also get rid of the pwm_set_period() call done in
pwm_apply_args(), because PWM users are now directly using pargs->period
instead of pwm_get_period(). By doing that we avoid messing with the
current PWM period.

The only remaining bit in pwm_apply_args() is the initial polarity
setting, and it should go away when all PWM users have been patched to
use the atomic API (with this API the polarity will be set along with
other PWM arguments when configuring the PWM).

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
---
 drivers/pwm/core.c  | 8 --------
 include/linux/pwm.h | 1 -
 2 files changed, 9 deletions(-)

diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index ac89529..26c3cf5 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -128,14 +128,6 @@ static int pwm_device_request(struct pwm_device *pwm, const char *label)
 	set_bit(PWMF_REQUESTED, &pwm->flags);
 	pwm->label = label;
 
-	/*
-	 * FIXME: this should be removed as soon as all PWM users are
-	 * properly making use of pwm_args to initialize the PWM device.
-	 * If we don't get rid of it, then PWM state and hardware can be
-	 * desynchronized.
-	 */
-	pwm_apply_args(pwm);
-
 	return 0;
 }
 
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index c8859b7..2f500a5 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -170,7 +170,6 @@ static inline void pwm_get_args(const struct pwm_device *pwm,
 
 static inline void pwm_apply_args(struct pwm_device *pwm)
 {
-	pwm_set_period(pwm, pwm->args.period);
 	pwm_set_polarity(pwm, pwm->args.polarity);
 }
 
-- 
2.5.0

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#1379259 — [PATCH v5 20/24] pwm: add the PWM initial state retrieval infra

Add a ->get_state() function to the pwm_ops struct to let PWM drivers
initialize the PWM state attached to a PWM device.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
---
 drivers/pwm/core.c  |  3 +++
 include/linux/pwm.h | 28 ++++++++++++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index c2759bc..0e7f687 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -270,6 +270,9 @@ 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);
 	}
 
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index 7bfeacf..73ca679 100644
--- a/include/linux/pwm.h
+++ b/include/linux/pwm.h
@@ -205,6 +205,29 @@ static inline void pwm_get_args(const struct pwm_device *pwm,
 
 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);
 }
 
@@ -216,6 +239,9 @@ 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
+ * @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
  */
@@ -228,6 +254,8 @@ 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);
+	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
-- 
2.5.0

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#1379260 — [PATCH v5 21/24] pwm: add the core infrastructure to allow atomic update

Add an ->apply() method to the pwm_ops struct to allow PWM drivers to
implement atomic update.
This method will be preferred over the ->enable(), ->disable() and
->config() methods if available.

Add the pwm_apply_state() function to the PWM user API.

Note that the pwm_apply_state() does not guarantee the atomicity of the
update operation, it all depends on the availability and implementation
of the ->apply() method.

pwm_enable/disable/set_polarity/config() are now implemented as wrappers
around the pwm_apply_state() function.

pwm_adjust_config() is allowing smooth handover between the bootloader
and the kernel. This function tries to adapt the current PWM state to
the PWM arguments coming from a PWM lookup table or a DT definition
without changing the duty_cycle/period proportion.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
---
 drivers/pwm/core.c  | 186 +++++++++++++++++++++++-------------
 include/linux/pwm.h | 269 +++++++++++++++++++++++++++++++++++-----------------
 2 files changed, 302 insertions(+), 153 deletions(-)

diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index 0e7f687..112a696 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -226,6 +226,19 @@ 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
@@ -244,8 +257,10 @@ 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);
@@ -431,102 +446,137 @@ 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 (err)
-		return err;
-
-	pwm->state.duty_cycle = duty_ns;
-	pwm->state.period = period_ns;
-
-	return 0;
-}
-EXPORT_SYMBOL_GPL(pwm_config);
+	if (!memcmp(state, &pwm->state, sizeof(*state)))
+		return 0;
 
-/**
- * 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.
- */
-int pwm_set_polarity(struct pwm_device *pwm, enum pwm_polarity polarity)
-{
-	int err;
+	if (pwm->chip->ops->apply) {
+		err = pwm->chip->ops->apply(pwm->chip, pwm, state);
+		if (err)
+			return err;
 
-	if (!pwm || !pwm->chip->ops)
-		return -EINVAL;
+		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;
+
+			/*
+			 * Changing the polarity of a running PWM is
+			 * only allowed when the PWM driver implements
+			 * ->apply().
+			 */
+			if (pwm->state.enabled) {
+				pwm->chip->ops->disable(pwm->chip, pwm);
+				pwm->state.enabled = false;
+			}
+
+			err = pwm->chip->ops->set_polarity(pwm->chip, pwm,
+							   state->polarity);
+			if (err)
+				return err;
+
+			pwm->state.polarity = state->polarity;
+		}
 
-	if (!pwm->chip->ops->set_polarity)
-		return -ENOSYS;
+		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))
-		return -EBUSY;
+			pwm->state.duty_cycle = state->duty_cycle;
+			pwm->state.period = state->period;
+		}
 
-	err = pwm->chip->ops->set_polarity(pwm->chip, pwm, polarity);
-	if (err)
-		return err;
+		if (state->enabled != pwm->state.enabled) {
+			if (state->enabled) {
+				err = pwm->chip->ops->enable(pwm->chip, pwm);
+				if (err)
+					return err;
+			} else {
+				pwm->chip->ops->disable(pwm->chip, pwm);
+			}
 
-	pwm->state.polarity = polarity;
+			pwm->state.enabled = state->enabled;
+		}
+	}
 
 	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);
+
+	/*
+	 * if the current period is zero this either means the PWM driver
+	 * does not support initial state retrieval or the PWM was not
+	 * configured.
+	 * In any case, we setup the new period and poloarity, and assign a
+	 * duty_cycle of 0.
+	 */
+	if (!state.period) {
+		state.duty_cycle = 0;
+		state.period = pargs.period;
+		state.polarity = pargs.polarity;
 
-	if (!pwm_is_enabled(pwm)) {
-		err = pwm->chip->ops->enable(pwm->chip, pwm);
-		if (!err)
-			pwm->state.enabled = true;
+		return pwm_apply_state(pwm, &state);
 	}
 
-	return err;
-}
-EXPORT_SYMBOL_GPL(pwm_enable);
+	/*
+	 * Adjust the PWM dutycycle/period based on the period value provided
+	 * in PWM args.
+	 */
+	if (pargs.period != state.period) {
+		u64 dutycycle = (u64)state.duty_cycle * pargs.period;
 
-/**
- * pwm_disable() - stop a PWM output toggling
- * @pwm: PWM device
- */
-void pwm_disable(struct pwm_device *pwm)
-{
-	if (!pwm)
-		return;
+		do_div(dutycycle, state.period);
+		state.duty_cycle = dutycycle;
+		state.period = pargs.period;
+	}
 
-	if (pwm_is_enabled(pwm)) {
-		pwm->chip->ops->disable(pwm->chip, pwm);
-		pwm->state.enabled = false;
+	/*
+	 * If the polarity changed, we should also change the dutycycle value.
+	 */
+	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)
 {
diff --git a/include/linux/pwm.h b/include/linux/pwm.h
index 73ca679..2ec9200 100644
--- a/include/linux/pwm.h
+++ b/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;
 
 /**
@@ -183,11 +131,6 @@ static inline unsigned int pwm_get_duty_cycle(const struct pwm_device *pwm)
 	return state.duty_cycle;
 }
 
-/*
- * pwm_set_polarity - configure the polarity of a PWM signal
- */
-int pwm_set_polarity(struct pwm_device *pwm, enum pwm_polarity polarity);
-
 static inline enum pwm_polarity pwm_get_polarity(const struct pwm_device *pwm)
 {
 	struct pwm_state state;
@@ -203,34 +146,6 @@ 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 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_ops - PWM controller operations
  * @request: optional hook for requesting a PWM
@@ -239,6 +154,10 @@ 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.
@@ -254,6 +173,8 @@ 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
@@ -291,6 +212,115 @@ 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);
 
@@ -316,6 +346,47 @@ 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;
@@ -387,6 +458,34 @@ 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;
-- 
2.5.0

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