linux-kernel - Re: [PATCH v8 04/11] pwm: max7360: Add MAX7360 PWM support

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Message-ID: <5eb7xqo7bfzath3xy7i6v5fep7qwfeg4z3rtzifmgnyvlc3o5b@yi6hzur52hl3>
Date: Tue, 13 May 2025 12:08:49 +0200
From: Uwe Kleine-König <ukleinek@...nel.org>
To: mathieu.dubois-briand@...tlin.com
Cc: Lee Jones <lee@...nel.org>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Kamel Bouhara <kamel.bouhara@...tlin.com>, Linus Walleij <linus.walleij@...aro.org>, 
	Bartosz Golaszewski <brgl@...ev.pl>, Dmitry Torokhov <dmitry.torokhov@...il.com>, 
	Michael Walle <mwalle@...nel.org>, Mark Brown <broonie@...nel.org>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "Rafael J. Wysocki" <rafael@...nel.org>, 
	Danilo Krummrich <dakr@...nel.org>, devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-gpio@...r.kernel.org, linux-input@...r.kernel.org, linux-pwm@...r.kernel.org, 
	andriy.shevchenko@...el.com, Grégory Clement <gregory.clement@...tlin.com>, 
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v8 04/11] pwm: max7360: Add MAX7360 PWM support

Hello,

On Fri, May 09, 2025 at 11:14:38AM +0200, mathieu.dubois-briand@...tlin.com wrote:
> From: Kamel Bouhara <kamel.bouhara@...tlin.com>
> 
> Add driver for Maxim Integrated MAX7360 PWM controller, supporting up to
> 8 independent PWM outputs.
> 
> Signed-off-by: Kamel Bouhara <kamel.bouhara@...tlin.com>
> Co-developed-by: Mathieu Dubois-Briand <mathieu.dubois-briand@...tlin.com>
> Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@...tlin.com>
> ---
>  drivers/pwm/Kconfig       |  10 +++
>  drivers/pwm/Makefile      |   1 +
>  drivers/pwm/pwm-max7360.c | 186 ++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 197 insertions(+)
> 
> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
> index 4731d5b90d7e..0b22141cbf85 100644
> --- a/drivers/pwm/Kconfig
> +++ b/drivers/pwm/Kconfig
> @@ -755,4 +755,14 @@ config PWM_XILINX
>  	  To compile this driver as a module, choose M here: the module
>  	  will be called pwm-xilinx.
>  
> +config PWM_MAX7360
> +	tristate "MAX7360 PWMs"
> +	depends on MFD_MAX7360
> +	help
> +	  PWM driver for Maxim Integrated MAX7360 multifunction device, with
> +	  support for up to 8 PWM outputs.
> +
> +	  To compile this driver as a module, choose M here: the module
> +	  will be called pwm-max7360.
> +
>  endif
> diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
> index 539e0def3f82..9c7701d8070b 100644
> --- a/drivers/pwm/Makefile
> +++ b/drivers/pwm/Makefile
> @@ -36,6 +36,7 @@ obj-$(CONFIG_PWM_LPC32XX)	+= pwm-lpc32xx.o
>  obj-$(CONFIG_PWM_LPSS)		+= pwm-lpss.o
>  obj-$(CONFIG_PWM_LPSS_PCI)	+= pwm-lpss-pci.o
>  obj-$(CONFIG_PWM_LPSS_PLATFORM)	+= pwm-lpss-platform.o
> +obj-$(CONFIG_PWM_MAX7360)	+= pwm-max7360.o
>  obj-$(CONFIG_PWM_MESON)		+= pwm-meson.o
>  obj-$(CONFIG_PWM_MEDIATEK)	+= pwm-mediatek.o
>  obj-$(CONFIG_PWM_MICROCHIP_CORE)	+= pwm-microchip-core.o
> diff --git a/drivers/pwm/pwm-max7360.c b/drivers/pwm/pwm-max7360.c
> new file mode 100644
> index 000000000000..af2006ec7a96
> --- /dev/null
> +++ b/drivers/pwm/pwm-max7360.c
> @@ -0,0 +1,186 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright 2025 Bootlin
> + *
> + * Author: Kamel BOUHARA <kamel.bouhara@...tlin.com>
> + * Author: Mathieu Dubois-Briand <mathieu.dubois-briand@...tlin.com>
> + *
> + * Limitations:
> + * - Only supports normal polarity.
> + * - The period is fixed to 2 ms.
> + * - Only the duty cycle can be changed, new values are applied at the beginning
> + *   of the next cycle.
> + * - When disabled, the output is put in Hi-Z.
> + */
> +#include <linux/bits.h>
> +#include <linux/dev_printk.h>
> +#include <linux/err.h>
> +#include <linux/math64.h>
> +#include <linux/mfd/max7360.h>
> +#include <linux/minmax.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/pwm.h>
> +#include <linux/regmap.h>
> +#include <linux/time.h>
> +#include <linux/types.h>
> +
> +#define MAX7360_NUM_PWMS			8
> +#define MAX7360_PWM_MAX_RES			255
> +#define MAX7360_PWM_PERIOD_NS			(2 * NSEC_PER_MSEC)
> +
> +struct max7360_pwm_waveform {
> +	u8 duty_steps;
> +	bool enabled;
> +};
> +
> +static int max7360_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
> +{
> +	struct regmap *regmap = pwmchip_get_drvdata(chip);
> +	int ret;
> +
> +	ret = regmap_write_bits(regmap, MAX7360_REG_PWMCFG(pwm->hwpwm),
> +				MAX7360_PORT_CFG_COMMON_PWM, 0);
> +	if (ret)
> +		return ret;
> +
> +	return regmap_write_bits(regmap, MAX7360_REG_PORTS, BIT(pwm->hwpwm), BIT(pwm->hwpwm));

What is the effect of these writes? It doesn't need to be undone in a
matching .free()?

> +}
> +
> +static int max7360_pwm_round_waveform_tohw(struct pwm_chip *chip,
> +					   struct pwm_device *pwm,
> +					   const struct pwm_waveform *wf,
> +					   void *_wfhw)
> +{
> +	struct max7360_pwm_waveform *wfhw = _wfhw;
> +	u64 duty_steps;
> +
> +	/*
> +	 * Ignore user provided values for period_length_ns and duty_offset_ns:
> +	 * we only support fixed period of MAX7360_PWM_PERIOD_NS and offset of 0.
> +	 */
> +	duty_steps = mul_u64_u64_div_u64(wf->duty_length_ns, MAX7360_PWM_MAX_RES,
> +					 MAX7360_PWM_PERIOD_NS);
> +
> +	wfhw->duty_steps = min(MAX7360_PWM_MAX_RES, duty_steps);
> +	wfhw->enabled = !!wf->duty_length_ns;
> +
> +	return 0;
> +}
> +
> +static int max7360_pwm_round_waveform_fromhw(struct pwm_chip *chip, struct pwm_device *pwm,
> +					     const void *_wfhw, struct pwm_waveform *wf)
> +{
> +	const struct max7360_pwm_waveform *wfhw = _wfhw;
> +
> +	wf->period_length_ns = wfhw->enabled ? MAX7360_PWM_PERIOD_NS : 0;
> +	wf->duty_offset_ns = 0;
> +	wf->duty_length_ns = DIV_ROUND_UP(wfhw->duty_steps * MAX7360_PWM_PERIOD_NS,
> +					  MAX7360_PWM_MAX_RES);
> +
> +	return 0;
> +}
> +
> +static int max7360_pwm_write_waveform(struct pwm_chip *chip,
> +				      struct pwm_device *pwm,
> +				      const void *_wfhw)
> +{
> +	struct regmap *regmap = pwmchip_get_drvdata(chip);
> +	const struct max7360_pwm_waveform *wfhw = _wfhw;
> +	unsigned int val;
> +	int ret;
> +
> +	val = wfhw->enabled ? BIT(pwm->hwpwm) : 0;
> +	ret = regmap_write_bits(regmap, MAX7360_REG_GPIOCTRL, BIT(pwm->hwpwm), val);
> +	if (ret)
> +		return ret;
> +
> +	if (wfhw->duty_steps)
> +		return regmap_write(regmap, MAX7360_REG_PWM(pwm->hwpwm), wfhw->duty_steps);

Would it make sense to first write duty_steps and only then enable?
Otherwise it might happen that you enable and still have a wrong duty
configuration in the MAX7360_REG_PWM register and emit a wrong period?

Do you need to write duty_steps = 0 if enabled is false?

> +	return 0;
> +}

Best regards
Uwe

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