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[v6,0/2] riscv: pwm: sophgo: add pwm support for CV1800

Message ID 20240406063413.3334639-1-qiujingbao.dlmu@gmail.com
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Series riscv: pwm: sophgo: add pwm support for CV1800 | expand

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Jingbao Qiu April 6, 2024, 6:34 a.m. UTC 
The Sophgo CV1800 chip provides a set of four independent
PWM channel outputs.
This series adds PWM controller support for Sophgo cv1800.

Changes since v5:
- delete the OE function because we plan to use the counter subsystem
  instead of capture, so there is no need to reuse this code.
- fix set polarity reverse error.

v5: https://lore.kernel.org/all/20240314100131.323540-1-qiujingbao.dlmu@gmail.com/

Changes since v4:
- drop filename
- fix macro
- optimize cv1800_pwm_set_polarity()
- optimize cv1800_pwm_set_oe()
- add comment for cv1800_pwm_set_oe()
- use ticks replace tem
- fix duty_cycle larger than period_val
- use devm_clk_rate_exclusive_get() replace
  clk_rate_exclusive_get()
- map linux polarity to register polarity 

v4: https://lore.kernel.org/all/20240304085933.1246964-1-qiujingbao.dlmu@gmail.com/

datasheet Link: https://github.com/milkv-duo/duo-files/blob/main/duo/datasheet/CV1800B-CV1801B-Preliminary-Datasheet-full-en.pdf
page 614

Changes since v3:
- use macro instead of npwm number
- add support for polarity feature
- add support for Output-Enable/OE feature

v3: https://lore.kernel.org/all/20240223082014.109385-1-qiujingbao.dlmu@gmail.com/

Changes since v2:
- use 0x08 instead of macro
- split if statements based on conditions
- in order to round up, first calculate the
  number of high-level cycles, then subtract
  it from the PERIOD to obtain the number of HLPERIOD
- use new pwmchip_alloc() API instead of old style

v2: https://lore.kernel.org/all/20240212121729.1086718-1-qiujingbao.dlmu@gmail.com/

Changes since v1:
- drop full stop from subject
- re-order maintainers and description
- pass checkpatch.pl --strict
- fix naming errors
- add "Limitations" section
- use a driver specific prefix for all defines
- using bool instead u32 in cv1800_pwm_enable
- check and set state->polarity
- use mul_u64_u64_div_u64
- use clk_rate_exclusive_get(), balance with clk_rate_exclusive_put()
- using macro definitions instead of shift operations
- remove shift operation on 0
- use priv replace cv_pwm
- hardcode npwm
- set atomic to true
- remove MODULE_ALIAS

v1: https://lore.kernel.org/all/20240207055856.672184-1-qiujingbao.dlmu@gmail.com/

Jingbao Qiu (2):
  dt-bindings: pwm: sophgo: add pwm for Sophgo CV1800 series SoC
  pwm: sophgo: add pwm support for Sophgo CV1800 SoC

 .../bindings/pwm/sophgo,cv1800-pwm.yaml       |  45 +++
 drivers/pwm/Kconfig                           |  10 +
 drivers/pwm/Makefile                          |   1 +
 drivers/pwm/pwm-cv1800.c                      | 296 ++++++++++++++++++
 4 files changed, 352 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/pwm/sophgo,cv1800-pwm.yaml
 create mode 100644 drivers/pwm/pwm-cv1800.c

Comments

Uwe Kleine-König April 29, 2024, 2:54 p.m. UTC | #1 
Hello,

On Sat, Apr 06, 2024 at 02:34:13PM +0800, Jingbao Qiu wrote:
> Implement the PWM driver for CV1800.
> 
> Signed-off-by: Jingbao Qiu <qiujingbao.dlmu@gmail.com>
> ---
>  drivers/pwm/Kconfig      |  10 ++
>  drivers/pwm/Makefile     |   1 +
>  drivers/pwm/pwm-cv1800.c | 296 +++++++++++++++++++++++++++++++++++++++
>  3 files changed, 307 insertions(+)
>  create mode 100644 drivers/pwm/pwm-cv1800.c
> 
> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
> index 1dd7921194f5..3869ca022aeb 100644
> --- a/drivers/pwm/Kconfig
> +++ b/drivers/pwm/Kconfig
> @@ -182,6 +182,16 @@ config PWM_CROS_EC
>  	  PWM driver for exposing a PWM attached to the ChromeOS Embedded
>  	  Controller.
>  
> +config PWM_CV1800
> +	tristate "Sophgo CV1800 PWM driver"
> +	depends on ARCH_SOPHGO || COMPILE_TEST
> +	help
> +	  Generic PWM framework driver for the Sophgo CV1800 series
> +	  SoCs.
> +
> +	  To compile this driver as a module, build the dependecies
> +	  as modules, this will be called pwm-cv1800.
> +
>  config PWM_DWC_CORE
>  	tristate
>  	depends on HAS_IOMEM
> diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
> index 90913519f11a..6295e2259efc 100644
> --- a/drivers/pwm/Makefile
> +++ b/drivers/pwm/Makefile
> @@ -14,6 +14,7 @@ obj-$(CONFIG_PWM_CLK)		+= pwm-clk.o
>  obj-$(CONFIG_PWM_CLPS711X)	+= pwm-clps711x.o
>  obj-$(CONFIG_PWM_CRC)		+= pwm-crc.o
>  obj-$(CONFIG_PWM_CROS_EC)	+= pwm-cros-ec.o
> +obj-$(CONFIG_PWM_CV1800)	+= pwm-cv1800.o
>  obj-$(CONFIG_PWM_DWC_CORE)	+= pwm-dwc-core.o
>  obj-$(CONFIG_PWM_DWC)		+= pwm-dwc.o
>  obj-$(CONFIG_PWM_EP93XX)	+= pwm-ep93xx.o
> diff --git a/drivers/pwm/pwm-cv1800.c b/drivers/pwm/pwm-cv1800.c
> new file mode 100644
> index 000000000000..37a6be3f63aa
> --- /dev/null
> +++ b/drivers/pwm/pwm-cv1800.c
> @@ -0,0 +1,296 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Sophgo CV1800 PWM driver
> + * Author: Jingbao Qiu <qiujingbao.dlmu@gmail.com>
> + *
> + * Limitations:
> + * - It output low when PWM channel disabled.

Just to be sure: the output is low independant of the POLARITY register?

> + * - This pwm device supports dynamic loading of PWM parameters. When PWMSTART
> + *   is written from 0 to 1, the register value (HLPERIODn, PERIODn) will be
> + *   temporarily stored inside the PWM. If you want to dynamically change the
> + *   waveform during PWM output, after writing the new value to HLPERIODn and
> + *   PERIODn, write 1 and then 0 to PWMUPDATE[n] to make the new value effective.
> + * - Supports up to Rate/2 output, and the lowest is about Rate/(2^30-1).
> + * - By setting HLPERIODn to 0, can produce 100% duty cycle.
> + * - This hardware could support inverted polarity. By default, the value of the
> + *   POLARITY register is 0x0. This means that HLPERIOD represents the number
> + *   of low level beats.
> + * - This hardware supports input mode and output mode, implemented through the
> + *   Output-Enable/OE register. However, this driver has not yet implemented
> + *   capture callback.
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/pwm.h>
> +#include <linux/regmap.h>
> +
> +#define PWM_CV1800_HLPERIOD_BASE    0x00
> +#define PWM_CV1800_PERIOD_BASE      0x04
> +#define PWM_CV1800_POLARITY         0x40
> +#define PWM_CV1800_START            0x44
> +#define PWM_CV1800_DONE             0x48
> +#define PWM_CV1800_UPDATE           0x4c
> +#define PWM_CV1800_OE               0xd0
> +
> +#define PWM_CV1800_HLPERIOD(n)      (PWM_CV1800_HLPERIOD_BASE + ((n)*0x08))
> +#define PWM_CV1800_PERIOD(n)        (PWM_CV1800_PERIOD_BASE + ((n)*0x08))
> +
> +#define PWM_CV1800_UPDATE_MASK(n)   (BIT(0) << (n))
> +#define PWM_CV1800_OE_MASK(n)       (BIT(0) << (n))
> +#define PWM_CV1800_START_MASK(n)    (BIT(0) << (n))
> +#define PWM_CV1800_POLARITY_MASK(n) (BIT(0) << (n))
> +
> +#define PWM_CV1800_MAXPERIOD        0x3fffffff
> +#define PWM_CV1800_MINPERIOD        2
> +#define PWM_CV1800_CHANNELS         4
> +#define PWM_CV1800_PERIOD_RESET     BIT(1)
> +#define PWM_CV1800_HLPERIOD_RESET   BIT(0)
> +#define PWM_CV1800_REG_DISABLE      0x00U
> +#define PWM_CV1800_REG_ENABLE(n)    (BIT(0) << (n))

BIT(n)?

> +
> +struct cv1800_pwm {
> +	struct regmap *map;
> +	struct clk *clk;
> +	unsigned long clk_rate;
> +};
> +
> +static inline struct cv1800_pwm *to_cv1800_pwm_dev(struct pwm_chip *chip)
> +{
> +	return pwmchip_get_drvdata(chip);
> +}
> +
> +static const struct regmap_config cv1800_pwm_regmap_config = {
> +	.reg_bits = 32,
> +	.val_bits = 32,
> +	.reg_stride = 4,
> +};
> +
> +static int cv1800_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm,
> +			     bool enable)
> +{
> +	struct cv1800_pwm *priv = to_cv1800_pwm_dev(chip);
> +	u32 pwm_enable, state;
> +
> +	regmap_read(priv->map, PWM_CV1800_START, &pwm_enable);
> +	pwm_enable &= PWM_CV1800_START_MASK(pwm->hwpwm);
> +
> +	/*
> +	 * If the parameters are changed during runtime, Register needs
> +	 * to be updated to take effect.
> +	 */
> +	if (pwm_enable && enable) {
> +		regmap_update_bits(priv->map, PWM_CV1800_UPDATE,
> +				   PWM_CV1800_UPDATE_MASK(pwm->hwpwm),
> +				   PWM_CV1800_REG_ENABLE(pwm->hwpwm));
> +		regmap_update_bits(priv->map, PWM_CV1800_UPDATE,
> +				   PWM_CV1800_UPDATE_MASK(pwm->hwpwm),
> +				   PWM_CV1800_REG_DISABLE);

I think using a plain 0 instead of PWM_CV1800_REG_DISABLE would be a tad
clearer.

> +	} else if (!pwm_enable && enable) {
> +		regmap_update_bits(priv->map, PWM_CV1800_START,
> +				   PWM_CV1800_START_MASK(pwm->hwpwm),
> +				   PWM_CV1800_REG_ENABLE(pwm->hwpwm));
> +	} else if (pwm_enable && !enable) {
> +		regmap_update_bits(priv->map, PWM_CV1800_START,
> +				   PWM_CV1800_START_MASK(pwm->hwpwm),
> +				   PWM_CV1800_REG_DISABLE);
> +	}
> +
> +	/* check and set OE/Output-Enable mode */
> +	regmap_read(priv->map, PWM_CV1800_OE, &state);
> +	state &= PWM_CV1800_OE_MASK(pwm->hwpwm);
> +
> +	if (state == PWM_CV1800_REG_DISABLE && enable)

Here I'd use:

	regmap_read(priv->map, PWM_CV1800_OE, &state);

	if ((state & BIT(pwm->hwpwm)) && enable)

> +		regmap_update_bits(priv->map, PWM_CV1800_OE,
> +				   PWM_CV1800_OE_MASK(pwm->hwpwm),
> +				   PWM_CV1800_REG_ENABLE(pwm->hwpwm));
> +
> +	return 0;
> +}
> +
> [...]
> +static int cv1800_pwm_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct cv1800_pwm *priv;
> +	struct pwm_chip *chip;
> +	void __iomem *base;
> +	int ret;
> +
> +	chip = devm_pwmchip_alloc(dev, PWM_CV1800_CHANNELS, sizeof(*priv));
> +	if (!chip)
> +		return PTR_ERR(chip);
> +	priv = to_cv1800_pwm_dev(chip);
> +
> +	base = devm_platform_ioremap_resource(pdev, 0);
> +	if (IS_ERR(base))
> +		return PTR_ERR(base);
> +
> +	priv->map = devm_regmap_init_mmio(&pdev->dev, base,
> +					  &cv1800_pwm_regmap_config);
> +	if (IS_ERR(priv->map))
> +		return PTR_ERR(priv->map);

devm_regmap_init_mmio() doesnt' emit an error message on failure, so
please add one here.

> +	priv->clk = devm_clk_get_enabled(&pdev->dev, NULL);
> +	if (IS_ERR(priv->clk))
> +		return dev_err_probe(&pdev->dev, PTR_ERR(priv->clk),
> +				     "clk not found\n");
> +

Best regards
Uwe
Jingbao Qiu April 30, 2024, 4:36 a.m. UTC | #2 
Hi, Uwe

On Mon, Apr 29, 2024 at 10:54 PM Uwe Kleine-König
<u.kleine-koenig@pengutronix.de> wrote:
>
> Hello,
>
> On Sat, Apr 06, 2024 at 02:34:13PM +0800, Jingbao Qiu wrote:
> > Implement the PWM driver for CV1800.
> >
> > Signed-off-by: Jingbao Qiu <qiujingbao.dlmu@gmail.com>
> > ---
> >  drivers/pwm/Kconfig      |  10 ++
> >  drivers/pwm/Makefile     |   1 +
> >  drivers/pwm/pwm-cv1800.c | 296 +++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 307 insertions(+)
> >  create mode 100644 drivers/pwm/pwm-cv1800.c
> >
> > diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
> > index 1dd7921194f5..3869ca022aeb 100644
> > --- a/drivers/pwm/Kconfig
> > +++ b/drivers/pwm/Kconfig
> > @@ -182,6 +182,16 @@ config PWM_CROS_EC
> >         PWM driver for exposing a PWM attached to the ChromeOS Embedded
> >         Controller.
> >
> > +config PWM_CV1800
> > +     tristate "Sophgo CV1800 PWM driver"
> > +     depends on ARCH_SOPHGO || COMPILE_TEST
> > +     help
> > +       Generic PWM framework driver for the Sophgo CV1800 series
> > +       SoCs.
> > +
> > +       To compile this driver as a module, build the dependecies
> > +       as modules, this will be called pwm-cv1800.
> > +
> >  config PWM_DWC_CORE
> >       tristate
> >       depends on HAS_IOMEM
> > diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
> > index 90913519f11a..6295e2259efc 100644
> > --- a/drivers/pwm/Makefile
> > +++ b/drivers/pwm/Makefile
> > @@ -14,6 +14,7 @@ obj-$(CONFIG_PWM_CLK)               += pwm-clk.o
> >  obj-$(CONFIG_PWM_CLPS711X)   += pwm-clps711x.o
> >  obj-$(CONFIG_PWM_CRC)                += pwm-crc.o
> >  obj-$(CONFIG_PWM_CROS_EC)    += pwm-cros-ec.o
> > +obj-$(CONFIG_PWM_CV1800)     += pwm-cv1800.o
> >  obj-$(CONFIG_PWM_DWC_CORE)   += pwm-dwc-core.o
> >  obj-$(CONFIG_PWM_DWC)                += pwm-dwc.o
> >  obj-$(CONFIG_PWM_EP93XX)     += pwm-ep93xx.o
> > diff --git a/drivers/pwm/pwm-cv1800.c b/drivers/pwm/pwm-cv1800.c
> > new file mode 100644
> > index 000000000000..37a6be3f63aa
> > --- /dev/null
> > +++ b/drivers/pwm/pwm-cv1800.c
> > @@ -0,0 +1,296 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * Sophgo CV1800 PWM driver
> > + * Author: Jingbao Qiu <qiujingbao.dlmu@gmail.com>
> > + *
> > + * Limitations:
> > + * - It output low when PWM channel disabled.
>
> Just to be sure: the output is low independant of the POLARITY register?

When the value of the POLARITY register is 1, the PWM outputs a high level.
When the value of the POLARITY register is 0, the PWM output is low.
Should I make this point here?

>
> > + * - This pwm device supports dynamic loading of PWM parameters. When PWMSTART
> > + *   is written from 0 to 1, the register value (HLPERIODn, PERIODn) will be
> > + *   temporarily stored inside the PWM. If you want to dynamically change the
> > + *   waveform during PWM output, after writing the new value to HLPERIODn and
> > + *   PERIODn, write 1 and then 0 to PWMUPDATE[n] to make the new value effective.
> > + * - Supports up to Rate/2 output, and the lowest is about Rate/(2^30-1).
> > + * - By setting HLPERIODn to 0, can produce 100% duty cycle.
> > + * - This hardware could support inverted polarity. By default, the value of the
> > + *   POLARITY register is 0x0. This means that HLPERIOD represents the number
> > + *   of low level beats.
> > + * - This hardware supports input mode and output mode, implemented through the
> > + *   Output-Enable/OE register. However, this driver has not yet implemented
> > + *   capture callback.
> > + */
> > +
> > +#include <linux/clk.h>
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/of.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/pwm.h>
> > +#include <linux/regmap.h>
> > +
> > +#define PWM_CV1800_HLPERIOD_BASE    0x00
> > +#define PWM_CV1800_PERIOD_BASE      0x04
> > +#define PWM_CV1800_POLARITY         0x40
> > +#define PWM_CV1800_START            0x44
> > +#define PWM_CV1800_DONE             0x48
> > +#define PWM_CV1800_UPDATE           0x4c
> > +#define PWM_CV1800_OE               0xd0
> > +
> > +#define PWM_CV1800_HLPERIOD(n)      (PWM_CV1800_HLPERIOD_BASE + ((n)*0x08))
> > +#define PWM_CV1800_PERIOD(n)        (PWM_CV1800_PERIOD_BASE + ((n)*0x08))
> > +
> > +#define PWM_CV1800_UPDATE_MASK(n)   (BIT(0) << (n))
> > +#define PWM_CV1800_OE_MASK(n)       (BIT(0) << (n))
> > +#define PWM_CV1800_START_MASK(n)    (BIT(0) << (n))
> > +#define PWM_CV1800_POLARITY_MASK(n) (BIT(0) << (n))
> > +
> > +#define PWM_CV1800_MAXPERIOD        0x3fffffff
> > +#define PWM_CV1800_MINPERIOD        2
> > +#define PWM_CV1800_CHANNELS         4
> > +#define PWM_CV1800_PERIOD_RESET     BIT(1)
> > +#define PWM_CV1800_HLPERIOD_RESET   BIT(0)
> > +#define PWM_CV1800_REG_DISABLE      0x00U
> > +#define PWM_CV1800_REG_ENABLE(n)    (BIT(0) << (n))
>
> BIT(n)?

yes, I will fix it.

>
> > +
> > +struct cv1800_pwm {
> > +     struct regmap *map;
> > +     struct clk *clk;
> > +     unsigned long clk_rate;
> > +};
> > +
> > +static inline struct cv1800_pwm *to_cv1800_pwm_dev(struct pwm_chip *chip)
> > +{
> > +     return pwmchip_get_drvdata(chip);
> > +}
> > +
> > +static const struct regmap_config cv1800_pwm_regmap_config = {
> > +     .reg_bits = 32,
> > +     .val_bits = 32,
> > +     .reg_stride = 4,
> > +};
> > +
> > +static int cv1800_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm,
> > +                          bool enable)
> > +{
> > +     struct cv1800_pwm *priv = to_cv1800_pwm_dev(chip);
> > +     u32 pwm_enable, state;
> > +
> > +     regmap_read(priv->map, PWM_CV1800_START, &pwm_enable);
> > +     pwm_enable &= PWM_CV1800_START_MASK(pwm->hwpwm);
> > +
> > +     /*
> > +      * If the parameters are changed during runtime, Register needs
> > +      * to be updated to take effect.
> > +      */
> > +     if (pwm_enable && enable) {
> > +             regmap_update_bits(priv->map, PWM_CV1800_UPDATE,
> > +                                PWM_CV1800_UPDATE_MASK(pwm->hwpwm),
> > +                                PWM_CV1800_REG_ENABLE(pwm->hwpwm));
> > +             regmap_update_bits(priv->map, PWM_CV1800_UPDATE,
> > +                                PWM_CV1800_UPDATE_MASK(pwm->hwpwm),
> > +                                PWM_CV1800_REG_DISABLE);
>
> I think using a plain 0 instead of PWM_CV1800_REG_DISABLE would be a tad
> clearer.

I will fix it.

>
> > +     } else if (!pwm_enable && enable) {
> > +             regmap_update_bits(priv->map, PWM_CV1800_START,
> > +                                PWM_CV1800_START_MASK(pwm->hwpwm),
> > +                                PWM_CV1800_REG_ENABLE(pwm->hwpwm));
> > +     } else if (pwm_enable && !enable) {
> > +             regmap_update_bits(priv->map, PWM_CV1800_START,
> > +                                PWM_CV1800_START_MASK(pwm->hwpwm),
> > +                                PWM_CV1800_REG_DISABLE);
> > +     }
> > +
> > +     /* check and set OE/Output-Enable mode */
> > +     regmap_read(priv->map, PWM_CV1800_OE, &state);
> > +     state &= PWM_CV1800_OE_MASK(pwm->hwpwm);
> > +
> > +     if (state == PWM_CV1800_REG_DISABLE && enable)
>
> Here I'd use:
>
>         regmap_read(priv->map, PWM_CV1800_OE, &state);
>
>         if ((state & BIT(pwm->hwpwm)) && enable)
>

I will fix it.

> > +             regmap_update_bits(priv->map, PWM_CV1800_OE,
> > +                                PWM_CV1800_OE_MASK(pwm->hwpwm),
> > +                                PWM_CV1800_REG_ENABLE(pwm->hwpwm));
> > +
> > +     return 0;
> > +}
> > +
> > [...]
> > +static int cv1800_pwm_probe(struct platform_device *pdev)
> > +{
> > +     struct device *dev = &pdev->dev;
> > +     struct cv1800_pwm *priv;
> > +     struct pwm_chip *chip;
> > +     void __iomem *base;
> > +     int ret;
> > +
> > +     chip = devm_pwmchip_alloc(dev, PWM_CV1800_CHANNELS, sizeof(*priv));
> > +     if (!chip)
> > +             return PTR_ERR(chip);
> > +     priv = to_cv1800_pwm_dev(chip);
> > +
> > +     base = devm_platform_ioremap_resource(pdev, 0);
> > +     if (IS_ERR(base))
> > +             return PTR_ERR(base);
> > +
> > +     priv->map = devm_regmap_init_mmio(&pdev->dev, base,
> > +                                       &cv1800_pwm_regmap_config);
> > +     if (IS_ERR(priv->map))
> > +             return PTR_ERR(priv->map);
>
> devm_regmap_init_mmio() doesnt' emit an error message on failure, so
> please add one here.

I will fix it.

Thank you for your suggestion.

Best regards
Jingbao Qiu
Uwe Kleine-König April 30, 2024, 8:06 a.m. UTC | #3 
Hello Jingbao,

On Tue, Apr 30, 2024 at 12:36:56PM +0800, Jingbao Qiu wrote:
> On Mon, Apr 29, 2024 at 10:54 PM Uwe Kleine-König
> <u.kleine-koenig@pengutronix.de> wrote:
> > On Sat, Apr 06, 2024 at 02:34:13PM +0800, Jingbao Qiu wrote:
> > > + * Limitations:
> > > + * - It output low when PWM channel disabled.
> >
> > Just to be sure: the output is low independant of the POLARITY register?
> 
> When the value of the POLARITY register is 1, the PWM outputs a high level.
> When the value of the POLARITY register is 0, the PWM output is low.
> Should I make this point here?

So that's: The hardware emits the inactive level when disabled.

Best regards
Uwe
Jingbao Qiu April 30, 2024, 12:47 p.m. UTC | #4 
On Tue, Apr 30, 2024 at 4:06 PM Uwe Kleine-König
<u.kleine-koenig@pengutronix.de> wrote:
>
> Hello Jingbao,
>
> On Tue, Apr 30, 2024 at 12:36:56PM +0800, Jingbao Qiu wrote:
> > On Mon, Apr 29, 2024 at 10:54 PM Uwe Kleine-König
> > <u.kleine-koenig@pengutronix.de> wrote:
> > > On Sat, Apr 06, 2024 at 02:34:13PM +0800, Jingbao Qiu wrote:
> > > > + * Limitations:
> > > > + * - It output low when PWM channel disabled.
> > >
> > > Just to be sure: the output is low independant of the POLARITY register?
> >
> > When the value of the POLARITY register is 1, the PWM outputs a high level.
> > When the value of the POLARITY register is 0, the PWM output is low.
> > Should I make this point here?
>
> So that's: The hardware emits the inactive level when disabled.
>

I will do that.

Best regards
Jingbao Qiu