[PATCH v2 2/2] pwm: dwc: add of/platform support

[dongxuyang@eswincomputing.com]

From: Xuyang Dong <dongxuyang@eswincomputing.com>

The dwc pwm controller can be used in non-PCI systems, so allow
either platform or OF based probing.

Co-developed-by: Ben Dooks <ben.dooks@codethink.co.uk>
Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Signed-off-by: Xiang Xu <xuxiang@eswincomputing.com>
Signed-off-by: Guosheng Wang <wangguosheng@eswincomputing.com>
Signed-off-by: Xuyang Dong <dongxuyang@eswincomputing.com>
---
 drivers/pwm/Kconfig        |  10 ++
 drivers/pwm/Makefile       |   1 +
 drivers/pwm/pwm-dwc-core.c | 101 +++++++++++++----
 drivers/pwm/pwm-dwc-of.c   | 216 +++++++++++++++++++++++++++++++++++++
 drivers/pwm/pwm-dwc.h      |  25 +++--
 5 files changed, 324 insertions(+), 29 deletions(-)
 create mode 100644 drivers/pwm/pwm-dwc-of.c

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 6f3147518376..50aea24b6168 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -249,6 +249,16 @@ config PWM_DWC
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-dwc.
 
+config PWM_DWC_OF
+	tristate "DesignWare PWM Controller (OF bus)"
+	depends on HAS_IOMEM && (OF || COMPILE_TEST)
+	select PWM_DWC_CORE
+	help
+	  PWM driver for Synopsys DWC PWM Controller on an OF bus or
+	  a platform bus.
+	  To compile this driver as a module, choose M here: the module
+	  will be called pwm-dwc-of.
+
 config PWM_EP93XX
 	tristate "Cirrus Logic EP93xx PWM support"
 	depends on ARCH_EP93XX || COMPILE_TEST
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index 0dc0d2b69025..470411a7e5ea 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -20,6 +20,7 @@ obj-$(CONFIG_PWM_CRC)		+= pwm-crc.o
 obj-$(CONFIG_PWM_CROS_EC)	+= pwm-cros-ec.o
 obj-$(CONFIG_PWM_DWC_CORE)	+= pwm-dwc-core.o
 obj-$(CONFIG_PWM_DWC)		+= pwm-dwc.o
+obj-$(CONFIG_PWM_DWC_OF)	+= pwm-dwc-of.o
 obj-$(CONFIG_PWM_EP93XX)	+= pwm-ep93xx.o
 obj-$(CONFIG_PWM_FSL_FTM)	+= pwm-fsl-ftm.o
 obj-$(CONFIG_PWM_GPIO)		+= pwm-gpio.o
diff --git a/drivers/pwm/pwm-dwc-core.c b/drivers/pwm/pwm-dwc-core.c
index 6dabec93a3c6..93b77dcde8d0 100644
--- a/drivers/pwm/pwm-dwc-core.c
+++ b/drivers/pwm/pwm-dwc-core.c
@@ -12,6 +12,7 @@
 #define DEFAULT_SYMBOL_NAMESPACE "dwc_pwm"
 
 #include <linux/bitops.h>
+#include <linux/clk.h>
 #include <linux/export.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
@@ -44,21 +45,52 @@ static int __dwc_pwm_configure_timer(struct dwc_pwm *dwc,
 	u32 high;
 	u32 low;
 
-	/*
-	 * Calculate width of low and high period in terms of input clock
-	 * periods and check are the result within HW limits between 1 and
-	 * 2^32 periods.
-	 */
-	tmp = DIV_ROUND_CLOSEST_ULL(state->duty_cycle, dwc->clk_ns);
-	if (tmp < 1 || tmp > (1ULL << 32))
-		return -ERANGE;
-	low = tmp - 1;
-
-	tmp = DIV_ROUND_CLOSEST_ULL(state->period - state->duty_cycle,
-				    dwc->clk_ns);
-	if (tmp < 1 || tmp > (1ULL << 32))
-		return -ERANGE;
-	high = tmp - 1;
+	if (dwc->clk)
+		dwc->clk_rate = clk_get_rate(dwc->clk);
+
+	if (dwc->features & DWC_TIM_CTRL_0N100PWM_EN) {
+		/*
+		 * Calculate width of low and high period in terms of input
+		 * clock periods and check are the result within HW limits
+		 * between 0 and 2^32 periods.
+		 */
+		tmp = state->duty_cycle * dwc->clk_rate;
+		tmp = DIV_ROUND_UP_ULL(tmp, NSEC_PER_SEC);
+		if (tmp > (1ULL << 32))
+			return -ERANGE;
+
+		if (pwm->args.polarity == PWM_POLARITY_INVERSED)
+			high = tmp;
+		else
+			low = tmp;
+
+		tmp = (state->period - state->duty_cycle) * dwc->clk_rate;
+		tmp = DIV_ROUND_UP_ULL(tmp, NSEC_PER_SEC);
+		if (tmp > (1ULL << 32))
+			return -ERANGE;
+
+		if (pwm->args.polarity == PWM_POLARITY_INVERSED)
+			low = tmp;
+		else
+			high = tmp;
+	} else {
+		/*
+		 * Calculate width of low and high period in terms of input
+		 * clock periods and check are the result within HW limits
+		 * between 1 and 2^32 periods.
+		 */
+		tmp = state->duty_cycle * dwc->clk_rate;
+		tmp = DIV_ROUND_UP_ULL(tmp, NSEC_PER_SEC);
+		if (tmp < 1 || tmp > (1ULL << 32))
+			return -ERANGE;
+		low = tmp - 1;
+
+		tmp = (state->period - state->duty_cycle) * dwc->clk_rate;
+		tmp = DIV_ROUND_UP_ULL(tmp, NSEC_PER_SEC);
+		if (tmp < 1 || tmp > (1ULL << 32))
+			return -ERANGE;
+		high = tmp - 1;
+	}
 
 	/*
 	 * Specification says timer usage flow is to disable timer, then
@@ -74,6 +106,7 @@ static int __dwc_pwm_configure_timer(struct dwc_pwm *dwc,
 	 * width of low period and latter the width of high period in terms
 	 * multiple of input clock periods:
 	 * Width = ((Count + 1) * input clock period).
+	 * Width = (Count * input clock period) : supported 0% and 100%).
 	 */
 	dwc_pwm_writel(dwc, low, DWC_TIM_LD_CNT(pwm->hwpwm));
 	dwc_pwm_writel(dwc, high, DWC_TIM_LD_CNT2(pwm->hwpwm));
@@ -85,6 +118,9 @@ static int __dwc_pwm_configure_timer(struct dwc_pwm *dwc,
 	 * periods are set by Load Count registers.
 	 */
 	ctrl = DWC_TIM_CTRL_MODE_USER | DWC_TIM_CTRL_PWM;
+	if (dwc->features & DWC_TIM_CTRL_0N100PWM_EN)
+		ctrl |= DWC_TIM_CTRL_0N100PWM_EN;
+
 	dwc_pwm_writel(dwc, ctrl, DWC_TIM_CTRL(pwm->hwpwm));
 
 	/*
@@ -121,11 +157,17 @@ static int dwc_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
 			     struct pwm_state *state)
 {
 	struct dwc_pwm *dwc = to_dwc_pwm(chip);
+	unsigned long clk_rate;
 	u64 duty, period;
 	u32 ctrl, ld, ld2;
 
 	pm_runtime_get_sync(pwmchip_parent(chip));
 
+	if (dwc->clk)
+		dwc->clk_rate = clk_get_rate(dwc->clk);
+
+	clk_rate = dwc->clk_rate;
+
 	ctrl = dwc_pwm_readl(dwc, DWC_TIM_CTRL(pwm->hwpwm));
 	ld = dwc_pwm_readl(dwc, DWC_TIM_LD_CNT(pwm->hwpwm));
 	ld2 = dwc_pwm_readl(dwc, DWC_TIM_LD_CNT2(pwm->hwpwm));
@@ -137,17 +179,32 @@ static int dwc_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
 	 * based on the timer load-count only.
 	 */
 	if (ctrl & DWC_TIM_CTRL_PWM) {
-		duty = (ld + 1) * dwc->clk_ns;
-		period = (ld2 + 1)  * dwc->clk_ns;
-		period += duty;
+		if (dwc->features & DWC_TIM_CTRL_0N100PWM_EN) {
+			if (pwm->args.polarity == PWM_POLARITY_INVERSED)
+				duty = ld2;
+			else
+				duty = ld;
+			period = ld + ld2;
+		} else {
+			duty = ld + 1;
+			period = ld2 + 1;
+			period += duty;
+		}
 	} else {
-		duty = (ld + 1) * dwc->clk_ns;
+		duty = ld + 1;
 		period = duty * 2;
 	}
 
 	state->polarity = PWM_POLARITY_INVERSED;
-	state->period = period;
-	state->duty_cycle = duty;
+	/*
+	 * If the ld register is at its maximum value. The duty value is
+	 * 4,294,967,295 (0xFFFF FFFF). The product (duty * NSEC_PER_SEC)
+	 * is guaranteed to be less than 2^64.
+	 */
+	duty *= NSEC_PER_SEC;
+	period *= NSEC_PER_SEC;
+	state->period = DIV_ROUND_UP_ULL(period, clk_rate);
+	state->duty_cycle = DIV_ROUND_UP_ULL(duty, clk_rate);
 
 	pm_runtime_put_sync(pwmchip_parent(chip));
 
@@ -169,7 +226,7 @@ struct pwm_chip *dwc_pwm_alloc(struct device *dev)
 		return chip;
 	dwc = to_dwc_pwm(chip);
 
-	dwc->clk_ns = 10;
+	dwc->clk_rate = NSEC_PER_SEC / 10;
 	chip->ops = &dwc_pwm_ops;
 
 	return chip;
diff --git a/drivers/pwm/pwm-dwc-of.c b/drivers/pwm/pwm-dwc-of.c
new file mode 100644
index 000000000000..df3b733b2c36
--- /dev/null
+++ b/drivers/pwm/pwm-dwc-of.c
@@ -0,0 +1,216 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * DesignWare PWM Controller driver OF
+ *
+ * Copyright (C) 2026 SiFive, Inc.
+ */
+
+#define DEFAULT_SYMBOL_NAMESPACE "dwc_pwm_of"
+
+#include <linux/clk.h>
+#include <linux/platform_device.h>
+#include <linux/pm_runtime.h>
+#include <linux/pwm.h>
+#include <linux/reset.h>
+
+#include "pwm-dwc.h"
+
+static int dwc_pwm_plat_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct dwc_pwm_drvdata *data;
+	struct pwm_chip *chip;
+	struct dwc_pwm *dwc;
+	u32 nr_pwm, tim_id;
+	int ret;
+
+	data = devm_kzalloc(dev, sizeof(struct dwc_pwm_drvdata), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	chip = dwc_pwm_alloc(dev);
+	if (IS_ERR(chip))
+		return dev_err_probe(dev, -ENOMEM, "failed to alloc pwm\n");
+
+	dwc = to_dwc_pwm(chip);
+
+	dwc->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(dwc->base))
+		return PTR_ERR(dwc->base);
+
+	if (!device_property_read_u32(dev, "snps,pwm-number", &nr_pwm)) {
+		if (nr_pwm > DWC_TIMERS_TOTAL)
+			dev_warn
+			(dev, "too many PWMs (%d) specified, capping at %d\n",
+			nr_pwm, chip->npwm);
+		else
+			chip->npwm = nr_pwm;
+	}
+
+	dwc->bus_clk = devm_clk_get_enabled(dev, "bus");
+	if (IS_ERR(dwc->bus_clk))
+		return dev_err_probe(dev, PTR_ERR(dwc->bus_clk),
+				     "failed to get bus clock\n");
+
+	dwc->clk = devm_clk_get_enabled(dev, "timer");
+	if (IS_ERR(dwc->clk))
+		return dev_err_probe(dev, PTR_ERR(dwc->clk),
+				     "failed to get timer clock\n");
+
+	ret = devm_clk_rate_exclusive_get(dev, dwc->clk);
+	if (ret)
+		return dev_err_probe(dev, ret,
+				     "failed to get exclusive rate\n");
+
+	dwc->clk_rate = clk_get_rate(dwc->clk);
+
+	dwc->rst = devm_reset_control_get_optional_exclusive_deasserted(dev,
+									NULL);
+	if (IS_ERR(dwc->rst))
+		return dev_err_probe(dev, PTR_ERR(dwc->rst),
+				     "failed to get reset control\n");
+
+	/* init PWM feature */
+	dwc->features = 0;
+	/*
+	 * Support for 0% and 100% duty cycle mode was added in version 2.11a
+	 * and later.
+	 */
+	tim_id = dwc_pwm_readl(dwc, DWC_TIMERS_COMP_VERSION);
+	if (tim_id >= DWC_TIM_VERSION_ID_2_11A)
+		dwc->features |= DWC_TIM_CTRL_0N100PWM_EN;
+
+	ret = devm_pwmchip_add(dev, chip);
+	if (ret)
+		return dev_err_probe(dev, ret, "failed to add pwmchip\n");
+
+	data->chips[0] = chip;
+	dev_set_drvdata(dev, data);
+
+	pm_runtime_set_autosuspend_delay(dev, 5000);
+	pm_runtime_use_autosuspend(dev);
+	devm_pm_runtime_enable(dev);
+
+	return 0;
+}
+
+static void dwc_pwm_plat_remove(struct platform_device *pdev)
+{
+	struct dwc_pwm_drvdata *data = platform_get_drvdata(pdev);
+	struct pwm_chip *chip = data->chips[0];
+
+	for (int idx = 0; idx < chip->npwm; idx++) {
+		if (chip->pwms[idx].state.enabled)
+			pwm_disable(&chip->pwms[idx]);
+	}
+}
+
+static int dwc_pwm_runtime_suspend(struct device *dev)
+{
+	struct dwc_pwm_drvdata *data = dev_get_drvdata(dev);
+	struct pwm_chip *chip = data->chips[0];
+	struct dwc_pwm *dwc = to_dwc_pwm(chip);
+
+	clk_disable_unprepare(dwc->clk);
+	clk_disable_unprepare(dwc->bus_clk);
+
+	return 0;
+}
+
+static int dwc_pwm_runtime_resume(struct device *dev)
+{
+	struct dwc_pwm_drvdata *data = dev_get_drvdata(dev);
+	struct pwm_chip *chip = data->chips[0];
+	struct dwc_pwm *dwc = to_dwc_pwm(chip);
+	int ret;
+
+	ret = clk_prepare_enable(dwc->bus_clk);
+	if (ret) {
+		dev_err(dev, "failed to enable bus clock: %d\n", ret);
+		return ret;
+	}
+
+	ret = clk_prepare_enable(dwc->clk);
+	if (ret) {
+		dev_err(dev, "failed to enable timer clock: %d\n", ret);
+		clk_disable_unprepare(dwc->bus_clk);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int dwc_pwm_suspend(struct device *dev)
+{
+	struct dwc_pwm_drvdata *data = dev_get_drvdata(dev);
+	struct pwm_chip *chip = data->chips[0];
+	struct dwc_pwm *dwc = to_dwc_pwm(chip);
+	int idx, ret;
+
+	for (idx = 0; idx < chip->npwm; idx++) {
+		if (chip->pwms[idx].state.enabled)
+			return -EBUSY;
+
+		dwc->ctx[idx].cnt = dwc_pwm_readl(dwc, DWC_TIM_LD_CNT(idx));
+		dwc->ctx[idx].cnt2 = dwc_pwm_readl(dwc, DWC_TIM_LD_CNT2(idx));
+		dwc->ctx[idx].ctrl = dwc_pwm_readl(dwc, DWC_TIM_CTRL(idx));
+	}
+
+	if (!pm_runtime_status_suspended(dev)) {
+		ret = dwc_pwm_runtime_suspend(dev);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+static int dwc_pwm_resume(struct device *dev)
+{
+	struct dwc_pwm_drvdata *data = dev_get_drvdata(dev);
+	struct pwm_chip *chip = data->chips[0];
+	struct dwc_pwm *dwc = to_dwc_pwm(chip);
+	int idx, ret;
+
+	if (!pm_runtime_status_suspended(dev)) {
+		ret = dwc_pwm_runtime_resume(dev);
+		if (ret)
+			return ret;
+	}
+
+	for (idx = 0; idx < chip->npwm; idx++) {
+		dwc_pwm_writel(dwc, dwc->ctx[idx].cnt, DWC_TIM_LD_CNT(idx));
+		dwc_pwm_writel(dwc, dwc->ctx[idx].cnt2, DWC_TIM_LD_CNT2(idx));
+		dwc_pwm_writel(dwc, dwc->ctx[idx].ctrl, DWC_TIM_CTRL(idx));
+	}
+
+	return 0;
+}
+
+static const struct dev_pm_ops dwc_pwm_pm_ops = {
+	RUNTIME_PM_OPS(dwc_pwm_runtime_suspend, dwc_pwm_runtime_resume, NULL)
+	SYSTEM_SLEEP_PM_OPS(dwc_pwm_suspend, dwc_pwm_resume)
+};
+
+static const struct of_device_id dwc_pwm_dt_ids[] = {
+	{ .compatible = "snps,dw-apb-timers-pwm2" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, dwc_pwm_dt_ids);
+
+static struct platform_driver dwc_pwm_plat_driver = {
+	.driver = {
+		.name = "dwc-pwm",
+		.pm = pm_sleep_ptr(&dwc_pwm_pm_ops),
+		.of_match_table = dwc_pwm_dt_ids,
+	},
+	.probe = dwc_pwm_plat_probe,
+	.remove = dwc_pwm_plat_remove,
+};
+
+module_platform_driver(dwc_pwm_plat_driver);
+
+MODULE_ALIAS("platform:dwc-pwm-of");
+MODULE_AUTHOR("Ben Dooks <ben.dooks@codethink.co.uk>");
+MODULE_DESCRIPTION("DesignWare PWM Controller");
+MODULE_LICENSE("GPL");
diff --git a/drivers/pwm/pwm-dwc.h b/drivers/pwm/pwm-dwc.h
index 1562594e7f85..75f7c2d031c4 100644
--- a/drivers/pwm/pwm-dwc.h
+++ b/drivers/pwm/pwm-dwc.h
@@ -26,12 +26,19 @@ MODULE_IMPORT_NS("dwc_pwm");
 #define DWC_TIMERS_TOTAL	8
 
 /* Timer Control Register */
-#define DWC_TIM_CTRL_EN		BIT(0)
-#define DWC_TIM_CTRL_MODE	BIT(1)
-#define DWC_TIM_CTRL_MODE_FREE	(0 << 1)
-#define DWC_TIM_CTRL_MODE_USER	(1 << 1)
-#define DWC_TIM_CTRL_INT_MASK	BIT(2)
-#define DWC_TIM_CTRL_PWM	BIT(3)
+#define DWC_TIM_CTRL_EN			BIT(0)
+#define DWC_TIM_CTRL_MODE		BIT(1)
+#define DWC_TIM_CTRL_MODE_FREE		(0 << 1)
+#define DWC_TIM_CTRL_MODE_USER		BIT(1)
+#define DWC_TIM_CTRL_INT_MASK		BIT(2)
+#define DWC_TIM_CTRL_PWM		BIT(3)
+#define DWC_TIM_CTRL_0N100PWM_EN	BIT(4)
+
+/*
+ * The version 2.11a and later add "Pulse Width Modulation with
+ * 0% and 100% Duty Cycle".
+ */
+#define DWC_TIM_VERSION_ID_2_11A	0x3231312a
 
 struct dwc_pwm_info {
 	unsigned int nr;
@@ -52,8 +59,12 @@ struct dwc_pwm_ctx {
 
 struct dwc_pwm {
 	void __iomem *base;
-	unsigned int clk_ns;
+	struct clk *bus_clk;
+	struct clk *clk;
+	unsigned long clk_rate;
+	struct reset_control *rst;
 	struct dwc_pwm_ctx ctx[DWC_TIMERS_TOTAL];
+	u32 features;
 };
 
 static inline struct dwc_pwm *to_dwc_pwm(struct pwm_chip *chip)
-- 
2.34.1