[PATCH v4 2/2] pwm: dwc: add of/platform support

dongxuyang
2026-04-15T09:51:09Z

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.

The controller is reset only when no PWM channel is enabled.
Otherwise, clocks are enabled and the runtime PM state is updated
to reflect the active hardware configuration.

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 | 331 +++++++++++++++++++++++++++++++++++++
drivers/pwm/pwm-dwc.h | 25 ++-
5 files changed, 439 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..55dd503842c3 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 = (u64)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..b6edddbfb2c6
--- /dev/null
+++ b/drivers/pwm/pwm-dwc-of.c
@@ -0,0 +1,331 @@
+// 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;
+ u32 ctrl[DWC_TIMERS_TOTAL];
+ struct pwm_chip *chip;
+ struct dwc_pwm *dwc;
+ bool pwm_en = false;
+ u32 nr_pwm, tim_id;
+ unsigned int i;
+ int ret;
+
+ data = devm_kzalloc(dev, struct_size(data, chips, 1), 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(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(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_array_get_optional_exclusive(dev);
+ if (IS_ERR(dwc->rst))
+ return dev_err_probe(dev, PTR_ERR(dwc->rst),
+ "failed to get reset control\n");
+
+ ret = clk_prepare_enable(dwc->bus_clk);
+ if (ret)
+ return dev_err_probe(dev, ret,
+ "failed to enable bus clock\n");
+
+ ret = clk_prepare_enable(dwc->clk);
+ if (ret) {
+ dev_err(dev, "failed to enable timer clock\n");
+ goto disable_busclk;
+ }
+
+ /*
+ * Check all channels to see if any channel is enabled.
+ * Read the control register of each channel and extract the enable bit
+ */
+ for (i = 0; i < chip->npwm; i++) {
+ ctrl[i] = dwc_pwm_readl(dwc, DWC_TIM_CTRL(i)) & DWC_TIM_CTRL_EN;
+ if (ctrl[i])
+ pwm_en = true;
+ }
+
+ /* Only issue reset when all channels are disabled */
+ if (!pwm_en) {
+ ret = reset_control_reset(dwc->rst);
+ if (ret) {
+ dev_err(dev, "failed to reset\n");
+ goto disable_clk;
+ }
+ }
+
+ /* 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) {
+ dev_err(dev, "failed to add pwm chip");
+ goto reset_assert;
+ }
+
+ data->chips[0] = chip;
+ dev_set_drvdata(dev, data);
+
+ /*
+ * If any PWM channel is enabled, mark device active and hold runtime PM
+ * references for each enabled channel. Otherwise, gate the clocks.
+ */
+ if (pwm_en) {
+ pm_runtime_set_active(dev);
+ for (i = 0; i < chip->npwm; i++) {
+ if (ctrl[i])
+ pm_runtime_get_noresume(dev);
+ }
+ } else {
+ clk_disable_unprepare(dwc->clk);
+ clk_disable_unprepare(dwc->bus_clk);
+ }
+
+ pm_runtime_enable(dev);
+
+ return 0;
+
+reset_assert:
+ reset_control_assert(dwc->rst);
+disable_clk:
+ clk_disable_unprepare(dwc->clk);
+disable_busclk:
+ clk_disable_unprepare(dwc->bus_clk);
+
+ return ret;
+}
+
+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];
+ struct dwc_pwm *dwc = to_dwc_pwm(chip);
+ bool pwm_en = false;
+ unsigned int idx;
+ bool pm_flags;
+
+ /*
+ * Resume the device if it is runtime suspended to allow
+ * safe register access.
+ */
+ pm_flags = pm_runtime_status_suspended(&pdev->dev);
+ if (pm_flags)
+ pm_runtime_get_sync(&pdev->dev);
+
+ for (idx = 0; idx < chip->npwm; idx++) {
+ if (dwc_pwm_readl(dwc, DWC_TIM_CTRL(idx)) & DWC_TIM_CTRL_EN) {
+ pwm_en = true;
+ pm_runtime_put_noidle(&pdev->dev);
+ }
+ }
+
+ /*
+ * Re-suspend the device if it was runtime suspended prior to
+ * the register access.
+ */
+ if (pm_flags)
+ pm_runtime_put_sync(&pdev->dev);
+
+ if (pwm_en) {
+ clk_disable_unprepare(dwc->clk);
+ clk_disable_unprepare(dwc->bus_clk);
+ }
+
+ pm_runtime_disable(&pdev->dev);
+ reset_control_assert(dwc->rst);
+}
+
+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);
+ unsigned int idx;
+ int ret;
+
+ if (pm_runtime_status_suspended(dev)) {
+ ret = dwc_pwm_runtime_resume(dev);
+ if (ret)
+ return 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));
+ }
+
+ 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);
+ unsigned int idx;
+ bool pm_flags;
+ int ret;
+
+ /* Check if device was runtime suspended before system resume */
+ pm_flags = pm_runtime_status_suspended(dev);
+ if (pm_flags) {
+ /*
+ * Use PM framework to resume device
+ * (calls dwc_pwm_runtime_resume)
+ */
+ ret = pm_runtime_get_sync(dev);
+ if (ret < 0)
+ return ret;
+ } else {
+ /*
+ * Device was active, but clocks might be off after system sleep
+ * Call runtime_resume directly to restore hardware state
+ */
+ 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));
+ }
+
+ if (pm_flags) {
+ /* Balance the refcount taken by pm_runtime_get_sync
+ * if it was used
+ */
+ ret = pm_runtime_put_sync(dev);
+ if (ret < 0)
+ return ret;
+ }
+
+ 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_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