Re: [PATCH v14 04/10] pwm: max7360: Add MAX7360 PWM support

Mathieu Dubois-Briand
2025-09-12T06:24:09Z

On Sun Aug 24, 2025 at 1:57 PM CEST, Mathieu Dubois-Briand wrote:
> From: Kamel Bouhara <kamel.bouhara@bootlin.com>
>
> Add driver for Maxim Integrated MAX7360 PWM controller, supporting up to
> 8 independent PWM outputs.
>
> Signed-off-by: Kamel Bouhara <kamel.bouhara@bootlin.com>
> Co-developed-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
> Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
> drivers/pwm/Kconfig | 10 +++
> drivers/pwm/Makefile | 1 +
> drivers/pwm/pwm-max7360.c | 209 ++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 220 insertions(+)
>
> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
> index f00ce973dddf..f2b1ce47de7f 100644
> --- a/drivers/pwm/Kconfig
> +++ b/drivers/pwm/Kconfig
> @@ -432,6 +432,16 @@ config PWM_LPSS_PLATFORM
> To compile this driver as a module, choose M here: the module
> will be called pwm-lpss-platform.
>
> +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.
> +
> config PWM_MC33XS2410
> tristate "MC33XS2410 PWM support"
> depends on OF
> diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
> index ff4f47e5fb7a..dfa8b4966ee1 100644
> --- a/drivers/pwm/Makefile
> +++ b/drivers/pwm/Makefile
> @@ -38,6 +38,7 @@ 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_MC33XS2410) += pwm-mc33xs2410.o
> obj-$(CONFIG_PWM_MEDIATEK) += pwm-mediatek.o
> obj-$(CONFIG_PWM_MESON) += pwm-meson.o
> diff --git a/drivers/pwm/pwm-max7360.c b/drivers/pwm/pwm-max7360.c
> new file mode 100644
> index 000000000000..ebf93a7aee5b
> --- /dev/null
> +++ b/drivers/pwm/pwm-max7360.c
> @@ -0,0 +1,209 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright 2025 Bootlin
> + *
> + * Author: Kamel BOUHARA <kamel.bouhara@bootlin.com>
> + * Author: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
> + *
> + * PWM functionality of the MAX7360 multi-function device.
> + * https://www.analog.com/media/en/technical-documentation/data-sheets/MAX7360.pdf
> + *
> + * 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 immediately.
> + */
> +#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 255
> +#define MAX7360_PWM_STEPS 256
> +#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);
> +
> + /*
> + * Make sure we use the individual PWM configuration register and not
> + * the global one.
> + * We never need to use the global one, so there is no need to revert
> + * that in the .free() callback.
> + */
> + return regmap_write_bits(regmap, MAX7360_REG_PWMCFG(pwm->hwpwm),
> + MAX7360_PORT_CFG_COMMON_PWM, 0);
> +}
> +
> +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.
> + * Values from 0 to 254 as duty_steps will provide duty cycles of 0/256
> + * to 254/256, while value 255 will provide a duty cycle of 100%.
> + */
> + if (wf->duty_length_ns >= MAX7360_PWM_PERIOD_NS) {
> + duty_steps = MAX7360_PWM_MAX;
> + } else {
> + duty_steps = (u32)wf->duty_length_ns * MAX7360_PWM_STEPS / MAX7360_PWM_PERIOD_NS;
> + if (duty_steps == MAX7360_PWM_MAX)
> + duty_steps = MAX7360_PWM_MAX - 1;
> + }
> +
> + wfhw->duty_steps = min(MAX7360_PWM_MAX, duty_steps);
> + wfhw->enabled = !!wf->period_length_ns;
> +
> + if (wf->period_length_ns && wf->period_length_ns < MAX7360_PWM_PERIOD_NS)
> + return 1;
> + else
> + 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;
> +
> + if (wfhw->enabled) {
> + if (wfhw->duty_steps == MAX7360_PWM_MAX)
> + wf->duty_length_ns = MAX7360_PWM_PERIOD_NS;
> + else
> + wf->duty_length_ns = DIV_ROUND_UP(wfhw->duty_steps * MAX7360_PWM_PERIOD_NS,
> + MAX7360_PWM_STEPS);
> + } else {
> + wf->duty_length_ns = 0;
> + }
> +
> + 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;
> +
> + if (wfhw->enabled) {
> + ret = regmap_write(regmap, MAX7360_REG_PWM(pwm->hwpwm), wfhw->duty_steps);
> + if (ret)
> + return ret;
> + }
> +
> + val = wfhw->enabled ? BIT(pwm->hwpwm) : 0;
> + return regmap_write_bits(regmap, MAX7360_REG_GPIOCTRL, BIT(pwm->hwpwm), val);
> +}
> +
> +static int max7360_pwm_read_waveform(struct pwm_chip *chip,
> + struct pwm_device *pwm,
> + void *_wfhw)
> +{
> + struct regmap *regmap = pwmchip_get_drvdata(chip);
> + struct max7360_pwm_waveform *wfhw = _wfhw;
> + unsigned int val;
> + int ret;
> +
> + ret = regmap_read(regmap, MAX7360_REG_GPIOCTRL, &val);
> + if (ret)
> + return ret;
> +
> + if (val & BIT(pwm->hwpwm)) {
> + wfhw->enabled = true;
> + ret = regmap_read(regmap, MAX7360_REG_PWM(pwm->hwpwm), &val);
> + if (ret)
> + return ret;
> +
> + wfhw->duty_steps = val;
> + } else {
> + wfhw->enabled = false;
> + wfhw->duty_steps = 0;
> + }
> +
> + return 0;
> +}
> +
> +static const struct pwm_ops max7360_pwm_ops = {
> + .request = max7360_pwm_request,
> + .round_waveform_tohw = max7360_pwm_round_waveform_tohw,
> + .round_waveform_fromhw = max7360_pwm_round_waveform_fromhw,
> + .read_waveform = max7360_pwm_read_waveform,
> + .write_waveform = max7360_pwm_write_waveform,
> +};
> +
> +static int max7360_pwm_probe(struct platform_device *pdev)
> +{
> + struct device *dev = &pdev->dev;
> + struct pwm_chip *chip;
> + struct regmap *regmap;
> + int ret;
> +
> + regmap = dev_get_regmap(dev->parent, NULL);
> + if (!regmap)
> + return dev_err_probe(dev, -ENODEV, "Could not get parent regmap\n");
> +
> + /*
> + * This MFD sub-device does not have any associated device tree node:
> + * properties are stored in the device node of the parent (MFD) device
> + * and this same node is used in phandles of client devices.
> + * Reuse this device tree node here, as otherwise the PWM subsystem
> + * would be confused by this topology.
> + */
> + device_set_of_node_from_dev(dev, dev->parent);
> +
> + chip = devm_pwmchip_alloc(dev, MAX7360_NUM_PWMS, 0);
> + if (IS_ERR(chip))
> + return PTR_ERR(chip);
> + chip->ops = &max7360_pwm_ops;
> +
> + pwmchip_set_drvdata(chip, regmap);
> +
> + ret = devm_pwmchip_add(dev, chip);
> + if (ret)
> + return dev_err_probe(dev, ret, "Failed to add PWM chip\n");
> +
> + return 0;
> +}
> +
> +static struct platform_driver max7360_pwm_driver = {
> + .driver = {
> + .name = "max7360-pwm",
> + .probe_type = PROBE_PREFER_ASYNCHRONOUS,
> + },
> + .probe = max7360_pwm_probe,
> +};
> +module_platform_driver(max7360_pwm_driver);
> +
> +MODULE_DESCRIPTION("MAX7360 PWM driver");
> +MODULE_AUTHOR("Kamel BOUHARA <kamel.bouhara@bootlin.com>");
> +MODULE_AUTHOR("Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>");
> +MODULE_LICENSE("GPL");

Hi Uwe,

Any thought about this new version? I believe I fixed all the points we
have been discussing previously.

Thanks,
Mathieu

--
Mathieu Dubois-Briand, Bootlin
Embedded Linux and Kernel engineering