Re: [PATCH 2/2] pwm: Add Nuvoton PWM controller support

[Sean Young <sean@mess.org>]

On Fri, Oct 18, 2024 at 03:48:57AM +0000, Chi-Wen Weng wrote:
> This commit adds a generic PWM framework driver for Nuvoton MA35D1
> PWM controller.
> 
> Signed-off-by: Chi-Wen Weng <cwweng.linux@gmail.com>
> ---
>  drivers/pwm/Kconfig      |   9 +++
>  drivers/pwm/Makefile     |   1 +
>  drivers/pwm/pwm-ma35d1.c | 169 +++++++++++++++++++++++++++++++++++++++
>  3 files changed, 179 insertions(+)
>  create mode 100644 drivers/pwm/pwm-ma35d1.c
> 
> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
> index 0915c1e7df16..97b9e83af020 100644
> --- a/drivers/pwm/Kconfig
> +++ b/drivers/pwm/Kconfig
> @@ -411,6 +411,15 @@ config PWM_LPSS_PLATFORM
>  	  To compile this driver as a module, choose M here: the module
>  	  will be called pwm-lpss-platform.
>  
> +config PWM_MA35D1
> +	tristate "Nuvoton MA35D1 PWM support"
> +	depends on ARCH_MA35 || COMPILE_TEST
> +	help
> +	  Generic PWM framework driver for Nuvoton MA35D1.
> +
> +	  To compile this driver as a module, choose M here: the module
> +	  will be called pwm-ma35d1.
> +
>  config PWM_MESON
>  	tristate "Amlogic Meson PWM driver"
>  	depends on ARCH_MESON || COMPILE_TEST
> diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
> index 9081e0c0e9e0..c1d3a1d8add0 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-$(CONFIG_PWM_MA35D1)	+= pwm-ma35d1.o
>  obj-$(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-ma35d1.c b/drivers/pwm/pwm-ma35d1.c
> new file mode 100644
> index 000000000000..dc2f1f494a91
> --- /dev/null
> +++ b/drivers/pwm/pwm-ma35d1.c
> @@ -0,0 +1,169 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Driver for the Nuvoton MA35D1 PWM controller
> + *
> + * Copyright (C) 2024 Nuvoton Corporation
> + *               Chi-Wen Weng <cwweng@nuvoton.com>
> + */
> +
> +#include <linux/mod_devicetable.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/pwm.h>
> +#include <linux/io.h>
> +#include <linux/clk.h>
> +#include <linux/math64.h>
> +
> +/* The following are registers for PWM controller */
> +#define REG_PWM_CTL0            (0x00)
> +#define REG_PWM_CNTEN           (0x20)
> +#define REG_PWM_PERIOD0         (0x30)
> +#define REG_PWM_CMPDAT0         (0x50)
> +#define REG_PWM_WGCTL0          (0xB0)
> +#define REG_PWM_POLCTL          (0xD4)
> +#define REG_PWM_POEN            (0xD8)
> +
> +#define PWM_TOTAL_CHANNELS      6
> +#define PWM_CH_REG_SIZE         4
> +
> +struct nuvoton_pwm {
> +	void __iomem *base;
> +	u64 clkrate;
> +};
> +
> +static inline struct nuvoton_pwm *to_nuvoton_pwm(struct pwm_chip *chip)
> +{
> +	return pwmchip_get_drvdata(chip);
> +}
> +
> +static int nuvoton_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> +			     const struct pwm_state *state)
> +{
> +	struct nuvoton_pwm *nvtpwm;
> +	unsigned int ch = pwm->hwpwm;
> +
> +	nvtpwm = to_nuvoton_pwm(chip);
> +	if (state->enabled) {
> +		u64 duty_cycles, period_cycles;
> +
> +		/* Calculate the duty and period cycles */
> +		duty_cycles = mul_u64_u64_div_u64(nvtpwm->clkrate,
> +						  state->duty_cycle, NSEC_PER_SEC);
> +		if (duty_cycles > 0xFFFF)
> +			duty_cycles = 0xFFFF;
> +
> +		period_cycles = mul_u64_u64_div_u64(nvtpwm->clkrate,
> +						    state->period, NSEC_PER_SEC);
> +		if (period_cycles > 0xFFFF)
> +			period_cycles = 0xFFFF;

If a period is not supported, return -EINVAL - maybe even do a dev_err().
Same for the duty cycle above. It might make sense to calculate the period
first, so that the error is more likely to be about the period than the
duty cycle.

Then again I don't know if all the drivers do this, but at least some of
them do.

> +
> +		/* Write the duty and period cycles to registers */
> +		writel(duty_cycles, nvtpwm->base + REG_PWM_CMPDAT0 + (ch * PWM_CH_REG_SIZE));
> +		writel(period_cycles, nvtpwm->base + REG_PWM_PERIOD0 + (ch * PWM_CH_REG_SIZE));
> +		/* Enable counter */
> +		writel(readl(nvtpwm->base + REG_PWM_CNTEN) | BIT(ch),
> +		       nvtpwm->base + REG_PWM_CNTEN);
> +		/* Enable output */
> +		writel(readl(nvtpwm->base + REG_PWM_POEN) | BIT(ch),
> +		       nvtpwm->base + REG_PWM_POEN);
> +	} else {
> +		/* Disable counter */
> +		writel(readl(nvtpwm->base + REG_PWM_CNTEN) & ~BIT(ch),
> +		       nvtpwm->base + REG_PWM_CNTEN);
> +		/* Disable output */
> +		writel(readl(nvtpwm->base + REG_PWM_POEN) & ~BIT(ch),
> +		       nvtpwm->base + REG_PWM_POEN);
> +	}
> +
> +	/* Set polarity state to register */
> +	if (state->polarity == PWM_POLARITY_NORMAL)
> +		writel(readl(nvtpwm->base + REG_PWM_POLCTL) & ~BIT(ch),
> +		       nvtpwm->base + REG_PWM_POLCTL);
> +	else
> +		writel(readl(nvtpwm->base + REG_PWM_POLCTL) | BIT(ch),
> +		       nvtpwm->base + REG_PWM_POLCTL);
> +
> +	return 0;
> +}
> +
> +static int nuvoton_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
> +				 struct pwm_state *state)
> +{
> +	struct nuvoton_pwm *nvtpwm;
> +	unsigned int duty_cycles, period_cycles, cnten, outen, polarity;
> +	unsigned int ch = pwm->hwpwm;
> +
> +	nvtpwm = to_nuvoton_pwm(chip);
> +
> +	cnten = readl(nvtpwm->base + REG_PWM_CNTEN);
> +	outen = readl(nvtpwm->base + REG_PWM_POEN);
> +	duty_cycles = readl(nvtpwm->base + REG_PWM_CMPDAT0 + (ch * PWM_CH_REG_SIZE));
> +	period_cycles = readl(nvtpwm->base + REG_PWM_PERIOD0 + (ch * PWM_CH_REG_SIZE));
> +	polarity = readl(nvtpwm->base + REG_PWM_POLCTL) & BIT(ch);
> +
> +	state->enabled = (cnten & BIT(ch)) && (outen & BIT(ch));
> +	state->polarity = polarity ? PWM_POLARITY_INVERSED : PWM_POLARITY_NORMAL;
> +	state->duty_cycle = DIV64_U64_ROUND_UP((u64)duty_cycles * NSEC_PER_SEC, nvtpwm->clkrate);
> +	state->period = DIV64_U64_ROUND_UP((u64)period_cycles * NSEC_PER_SEC, nvtpwm->clkrate);
> +
> +	return 0;
> +}
> +
> +static const struct pwm_ops nuvoton_pwm_ops = {
> +	.apply = nuvoton_pwm_apply,
> +	.get_state = nuvoton_pwm_get_state,
> +};
> +
> +static int nuvoton_pwm_probe(struct platform_device *pdev)
> +{
> +	struct pwm_chip *chip;
> +	struct nuvoton_pwm *nvtpwm;
> +	struct clk *clk;
> +	int ret;
> +
> +	chip = devm_pwmchip_alloc(&pdev->dev, PWM_TOTAL_CHANNELS, sizeof(*nvtpwm));
> +	if (IS_ERR(chip))
> +		return PTR_ERR(chip);
> +
> +	nvtpwm = to_nuvoton_pwm(chip);
> +
> +	nvtpwm->base = devm_platform_ioremap_resource(pdev, 0);
> +	if (IS_ERR(nvtpwm->base))
> +		return PTR_ERR(nvtpwm->base);
> +
> +	clk = devm_clk_get_enabled(&pdev->dev, NULL);
> +	if (IS_ERR(clk))
> +		return dev_err_probe(&pdev->dev, PTR_ERR(clk), "unable to get the clock");
> +
> +	nvtpwm->clkrate = clk_get_rate(clk);
> +	if (nvtpwm->clkrate > NSEC_PER_SEC)
> +		return dev_err_probe(&pdev->dev, -EINVAL, "pwm clock out of range");
> +
> +	chip->ops = &nuvoton_pwm_ops;

I think you can add chip->atomic = true; here


Sean

> +
> +	ret = devm_pwmchip_add(&pdev->dev, chip);
> +	if (ret < 0)
> +		return dev_err_probe(&pdev->dev, ret, "unable to add pwm chip");
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id nuvoton_pwm_of_match[] = {
> +	{ .compatible = "nuvoton,ma35d1-pwm" },
> +	{}
> +};
> +MODULE_DEVICE_TABLE(of, nuvoton_pwm_of_match);
> +
> +static struct platform_driver nuvoton_pwm_driver = {
> +	.probe = nuvoton_pwm_probe,
> +	.driver = {
> +		.name = "nuvoton-pwm",
> +		.of_match_table = nuvoton_pwm_of_match,
> +	},
> +};
> +module_platform_driver(nuvoton_pwm_driver);
> +
> +MODULE_ALIAS("platform:nuvoton-pwm");
> +MODULE_AUTHOR("Chi-Wen Weng <cwweng@nuvoton.com>");
> +MODULE_DESCRIPTION("Nuvoton MA35D1 PWM driver");
> +MODULE_LICENSE("GPL");
> -- 
> 2.25.1
>