pwm: Add Loongson PWM controller support

This commit adds a generic PWM framework driver for the PWM controller
found on Loongson family chips.

Acked-by: Huacai Chen <chenhuacai@loongson.cn>
Co-developed-by: Juxin Gao <gaojuxin@loongson.cn>
Signed-off-by: Juxin Gao <gaojuxin@loongson.cn>
Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn>
Link: https://lore.kernel.org/r/76050a903a8015422fb9261ad88c7d9cc2edbbd8.1743403075.git.zhoubinbin@loongson.cn
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>

MAINTAINERS

@@ -13917,6 +13917,7 @@ M:	Binbin Zhou <zhoubinbin@loongson.cn>
 L:	linux-pwm@vger.kernel.org
 S:	Maintained
 F:	Documentation/devicetree/bindings/pwm/loongson,ls7a-pwm.yaml
+F:	drivers/pwm/pwm-loongson.c
 
 LOONGSON-2 SOC SERIES CLOCK DRIVER
 M:	Yinbo Zhu <zhuyinbo@loongson.cn>

drivers/pwm/Kconfig

@@ -351,6 +351,18 @@ config PWM_KEEMBAY
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-keembay.
 
+config PWM_LOONGSON
+	tristate "Loongson PWM support"
+	depends on MACH_LOONGSON64 || COMPILE_TEST
+	depends on COMMON_CLK
+	help
+	  Generic PWM framework driver for Loongson family.
+	  It can be found on Loongson-2K series cpus and Loongson LS7A
+	  bridge chips.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pwm-loongson.
+
 config PWM_LP3943
 	tristate "TI/National Semiconductor LP3943 PWM support"
 	depends on MFD_LP3943

drivers/pwm/Makefile

@@ -30,6 +30,7 @@ obj-$(CONFIG_PWM_INTEL_LGM)	+= pwm-intel-lgm.o
 obj-$(CONFIG_PWM_IQS620A)	+= pwm-iqs620a.o
 obj-$(CONFIG_PWM_JZ4740)	+= pwm-jz4740.o
 obj-$(CONFIG_PWM_KEEMBAY)	+= pwm-keembay.o
+obj-$(CONFIG_PWM_LOONGSON)	+= pwm-loongson.o
 obj-$(CONFIG_PWM_LP3943)	+= pwm-lp3943.o
 obj-$(CONFIG_PWM_LPC18XX_SCT)	+= pwm-lpc18xx-sct.o
 obj-$(CONFIG_PWM_LPC32XX)	+= pwm-lpc32xx.o

drivers/pwm/pwm-loongson.c

@@ -0,0 +1,290 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2017-2025 Loongson Technology Corporation Limited.
+ *
+ * Loongson PWM driver
+ *
+ * For Loongson's PWM IP block documentation please refer Chapter 11 of
+ * Reference Manual: https://loongson.github.io/LoongArch-Documentation/Loongson-7A1000-usermanual-EN.pdf
+ *
+ * Author: Juxin Gao <gaojuxin@loongson.cn>
+ * Further cleanup and restructuring by:
+ *         Binbin Zhou <zhoubinbin@loongson.cn>
+ *
+ * Limitations:
+ * - If both DUTY and PERIOD are set to 0, the output is a constant low signal.
+ * - When disabled the output is driven to 0 independent of the configured
+ *   polarity.
+ * - If the register is reconfigured while PWM is running, it does not complete
+ *   the currently running period.
+ * - Disabling the PWM stops the output immediately (without waiting for current
+ *   period to complete first).
+ */
+
+#include <linux/acpi.h>
+#include <linux/clk.h>
+#include <linux/device.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+#include <linux/units.h>
+
+/* Loongson PWM registers */
+#define LOONGSON_PWM_REG_DUTY		0x4 /* Low Pulse Buffer Register */
+#define LOONGSON_PWM_REG_PERIOD		0x8 /* Pulse Period Buffer Register */
+#define LOONGSON_PWM_REG_CTRL		0xc /* Control Register */
+
+/* Control register bits */
+#define LOONGSON_PWM_CTRL_REG_EN	BIT(0)  /* Counter Enable Bit */
+#define LOONGSON_PWM_CTRL_REG_OE	BIT(3)  /* Pulse Output Enable Control Bit, Valid Low */
+#define LOONGSON_PWM_CTRL_REG_SINGLE	BIT(4)  /* Single Pulse Control Bit */
+#define LOONGSON_PWM_CTRL_REG_INTE	BIT(5)  /* Interrupt Enable Bit */
+#define LOONGSON_PWM_CTRL_REG_INT	BIT(6)  /* Interrupt Bit */
+#define LOONGSON_PWM_CTRL_REG_RST	BIT(7)  /* Counter Reset Bit */
+#define LOONGSON_PWM_CTRL_REG_CAPTE	BIT(8)  /* Measurement Pulse Enable Bit */
+#define LOONGSON_PWM_CTRL_REG_INVERT	BIT(9)  /* Output flip-flop Enable Bit */
+#define LOONGSON_PWM_CTRL_REG_DZONE	BIT(10) /* Anti-dead Zone Enable Bit */
+
+/* default input clk frequency for the ACPI case */
+#define LOONGSON_PWM_FREQ_DEFAULT	50000 /* Hz */
+
+struct pwm_loongson_ddata {
+	struct clk *clk;
+	void __iomem *base;
+	u64 clk_rate;
+};
+
+static inline __pure struct pwm_loongson_ddata *to_pwm_loongson_ddata(struct pwm_chip *chip)
+{
+	return pwmchip_get_drvdata(chip);
+}
+
+static inline u32 pwm_loongson_readl(struct pwm_loongson_ddata *ddata, u32 offset)
+{
+	return readl(ddata->base + offset);
+}
+
+static inline void pwm_loongson_writel(struct pwm_loongson_ddata *ddata,
+				       u32 val, u32 offset)
+{
+	writel(val, ddata->base + offset);
+}
+
+static int pwm_loongson_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
+				     enum pwm_polarity polarity)
+{
+	u16 val;
+	struct pwm_loongson_ddata *ddata = to_pwm_loongson_ddata(chip);
+
+	val = pwm_loongson_readl(ddata, LOONGSON_PWM_REG_CTRL);
+
+	if (polarity == PWM_POLARITY_INVERSED)
+		/* Duty cycle defines LOW period of PWM */
+		val |= LOONGSON_PWM_CTRL_REG_INVERT;
+	else
+		/* Duty cycle defines HIGH period of PWM */
+		val &= ~LOONGSON_PWM_CTRL_REG_INVERT;
+
+	pwm_loongson_writel(ddata, val, LOONGSON_PWM_REG_CTRL);
+
+	return 0;
+}
+
+static void pwm_loongson_disable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	u32 val;
+	struct pwm_loongson_ddata *ddata = to_pwm_loongson_ddata(chip);
+
+	val = pwm_loongson_readl(ddata, LOONGSON_PWM_REG_CTRL);
+	val &= ~LOONGSON_PWM_CTRL_REG_EN;
+	pwm_loongson_writel(ddata, val, LOONGSON_PWM_REG_CTRL);
+}
+
+static int pwm_loongson_enable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	u32 val;
+	struct pwm_loongson_ddata *ddata = to_pwm_loongson_ddata(chip);
+
+	val = pwm_loongson_readl(ddata, LOONGSON_PWM_REG_CTRL);
+	val |= LOONGSON_PWM_CTRL_REG_EN;
+	pwm_loongson_writel(ddata, val, LOONGSON_PWM_REG_CTRL);
+
+	return 0;
+}
+
+static int pwm_loongson_config(struct pwm_chip *chip, struct pwm_device *pwm,
+			       u64 duty_ns, u64 period_ns)
+{
+	u32 duty, period;
+	struct pwm_loongson_ddata *ddata = to_pwm_loongson_ddata(chip);
+
+	/* duty = duty_ns * ddata->clk_rate / NSEC_PER_SEC */
+	duty = mul_u64_u64_div_u64(duty_ns, ddata->clk_rate, NSEC_PER_SEC);
+	if (duty > U32_MAX)
+		duty = U32_MAX;
+
+	/* period = period_ns * ddata->clk_rate / NSEC_PER_SEC */
+	period = mul_u64_u64_div_u64(period_ns, ddata->clk_rate, NSEC_PER_SEC);
+	if (period > U32_MAX)
+		period = U32_MAX;
+
+	pwm_loongson_writel(ddata, duty, LOONGSON_PWM_REG_DUTY);
+	pwm_loongson_writel(ddata, period, LOONGSON_PWM_REG_PERIOD);
+
+	return 0;
+}
+
+static int pwm_loongson_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			      const struct pwm_state *state)
+{
+	int ret;
+	bool enabled = pwm->state.enabled;
+
+	if (!state->enabled) {
+		if (enabled)
+			pwm_loongson_disable(chip, pwm);
+		return 0;
+	}
+
+	ret = pwm_loongson_set_polarity(chip, pwm, state->polarity);
+	if (ret)
+		return ret;
+
+	ret = pwm_loongson_config(chip, pwm, state->duty_cycle, state->period);
+	if (ret)
+		return ret;
+
+	if (!enabled && state->enabled)
+		ret = pwm_loongson_enable(chip, pwm);
+
+	return ret;
+}
+
+static int pwm_loongson_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
+				  struct pwm_state *state)
+{
+	u32 duty, period, ctrl;
+	struct pwm_loongson_ddata *ddata = to_pwm_loongson_ddata(chip);
+
+	duty = pwm_loongson_readl(ddata, LOONGSON_PWM_REG_DUTY);
+	period = pwm_loongson_readl(ddata, LOONGSON_PWM_REG_PERIOD);
+	ctrl = pwm_loongson_readl(ddata, LOONGSON_PWM_REG_CTRL);
+
+	/* duty & period have a max of 2^32, so we can't overflow */
+	state->duty_cycle = DIV64_U64_ROUND_UP((u64)duty * NSEC_PER_SEC, ddata->clk_rate);
+	state->period = DIV64_U64_ROUND_UP((u64)period * NSEC_PER_SEC, ddata->clk_rate);
+	state->polarity = (ctrl & LOONGSON_PWM_CTRL_REG_INVERT) ? PWM_POLARITY_INVERSED :
+			  PWM_POLARITY_NORMAL;
+	state->enabled = (ctrl & LOONGSON_PWM_CTRL_REG_EN) ? true : false;
+
+	return 0;
+}
+
+static const struct pwm_ops pwm_loongson_ops = {
+	.apply = pwm_loongson_apply,
+	.get_state = pwm_loongson_get_state,
+};
+
+static int pwm_loongson_probe(struct platform_device *pdev)
+{
+	int ret;
+	struct pwm_chip *chip;
+	struct pwm_loongson_ddata *ddata;
+	struct device *dev = &pdev->dev;
+
+	chip = devm_pwmchip_alloc(dev, 1, sizeof(*ddata));
+	if (IS_ERR(chip))
+		return PTR_ERR(chip);
+	ddata = to_pwm_loongson_ddata(chip);
+
+	ddata->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(ddata->base))
+		return PTR_ERR(ddata->base);
+
+	ddata->clk = devm_clk_get_optional_enabled(dev, NULL);
+	if (IS_ERR(ddata->clk))
+		return dev_err_probe(dev, PTR_ERR(ddata->clk),
+				     "Failed to get pwm clock\n");
+	if (ddata->clk) {
+		ret = devm_clk_rate_exclusive_get(dev, ddata->clk);
+		if (ret)
+			return dev_err_probe(dev, PTR_ERR(ddata->clk),
+					     "Failed to get exclusive rate\n");
+
+		ddata->clk_rate = clk_get_rate(ddata->clk);
+		if (!ddata->clk_rate)
+			return dev_err_probe(dev, -EINVAL,
+					     "Failed to get frequency\n");
+	} else {
+		ddata->clk_rate = LOONGSON_PWM_FREQ_DEFAULT;
+	}
+
+	/* This check is done to prevent an overflow in .apply */
+	if (ddata->clk_rate > NSEC_PER_SEC)
+		return dev_err_probe(dev, -EINVAL, "PWM clock out of range\n");
+
+	chip->ops = &pwm_loongson_ops;
+	chip->atomic = true;
+	dev_set_drvdata(dev, chip);
+
+	ret = devm_pwmchip_add(dev, chip);
+	if (ret < 0)
+		return dev_err_probe(dev, ret, "Failed to add PWM chip\n");
+
+	return 0;
+}
+
+static int pwm_loongson_suspend(struct device *dev)
+{
+	struct pwm_chip *chip = dev_get_drvdata(dev);
+	struct pwm_loongson_ddata *ddata = to_pwm_loongson_ddata(chip);
+	struct pwm_device *pwm = &chip->pwms[0];
+
+	if (pwm->state.enabled)
+		return -EBUSY;
+
+	clk_disable_unprepare(ddata->clk);
+
+	return 0;
+}
+
+static int pwm_loongson_resume(struct device *dev)
+{
+	struct pwm_chip *chip = dev_get_drvdata(dev);
+	struct pwm_loongson_ddata *ddata = to_pwm_loongson_ddata(chip);
+
+	return clk_prepare_enable(ddata->clk);
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(pwm_loongson_pm_ops, pwm_loongson_suspend,
+				pwm_loongson_resume);
+
+static const struct of_device_id pwm_loongson_of_ids[] = {
+	{ .compatible = "loongson,ls7a-pwm" },
+	{ /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, pwm_loongson_of_ids);
+
+static const struct acpi_device_id pwm_loongson_acpi_ids[] = {
+	{ "LOON0006" },
+	{ }
+};
+MODULE_DEVICE_TABLE(acpi, pwm_loongson_acpi_ids);
+
+static struct platform_driver pwm_loongson_driver = {
+	.probe = pwm_loongson_probe,
+	.driver = {
+		.name = "loongson-pwm",
+		.pm = pm_ptr(&pwm_loongson_pm_ops),
+		.of_match_table = pwm_loongson_of_ids,
+		.acpi_match_table = pwm_loongson_acpi_ids,
+	},
+};
+module_platform_driver(pwm_loongson_driver);
+
+MODULE_DESCRIPTION("Loongson PWM driver");
+MODULE_AUTHOR("Loongson Technology Corporation Limited.");
+MODULE_LICENSE("GPL");