[PATCH v3 2/2] pwm: add Axiado AX3000 PWM driver

The Axiado AX3000 and AX3005 SoCs include PWM controllers that can be
used to generate configurable PWM output signals.

Add a PWM driver with support for configuring period, duty cycle, and
enable state through the Linux PWM framework.

Signed-off-by: Petar Stepanovic <[email protected]>
---
 MAINTAINERS              |   1 +
 drivers/pwm/Kconfig      |  11 ++
 drivers/pwm/Makefile     |   1 +
 drivers/pwm/pwm-axiado.c | 310 +++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 323 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 9999480376cc..14eea3bc4d4d 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4319,6 +4319,7 @@ M:	Prasad Bolisetty <[email protected]>
 L:	[email protected]
 S:	Supported
 F:	Documentation/devicetree/bindings/pwm/axiado,ax3000-pwm.yaml
+F:	drivers/pwm/pwm-axiado.c
 
 AXIS ARTPEC ARM64 SoC SUPPORT
 M:	Jesper Nilsson <[email protected]>
diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 6f3147518376..76f6c04b0e23 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -129,6 +129,17 @@ config PWM_ATMEL_TCB
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-atmel-tcb.
 
+config PWM_AXIADO
+	tristate "Axiado PWM support"
+	depends on ARCH_AXIADO || COMPILE_TEST
+	depends on HAS_IOMEM
+	help
+	  PWM framework driver for the PWM controller found on Axiado
+	  AX3000 and AX3005 SoCs.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pwm-axiado.
+
 config PWM_AXI_PWMGEN
 	tristate "Analog Devices AXI PWM generator"
 	depends on MICROBLAZE || NIOS2 || ARCH_ZYNQ || ARCH_ZYNQMP || ARCH_INTEL_SOCFPGA || COMPILE_TEST
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index 0dc0d2b69025..4466a29e780a 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -8,6 +8,7 @@ obj-$(CONFIG_PWM_ARGON_FAN_HAT)	+= pwm-argon-fan-hat.o
 obj-$(CONFIG_PWM_ATMEL)		+= pwm-atmel.o
 obj-$(CONFIG_PWM_ATMEL_HLCDC_PWM)	+= pwm-atmel-hlcdc.o
 obj-$(CONFIG_PWM_ATMEL_TCB)	+= pwm-atmel-tcb.o
+obj-$(CONFIG_PWM_AXIADO)	+= pwm-axiado.o
 obj-$(CONFIG_PWM_AXI_PWMGEN)	+= pwm-axi-pwmgen.o
 obj-$(CONFIG_PWM_BCM2835)	+= pwm-bcm2835.o
 obj-$(CONFIG_PWM_BCM_IPROC)	+= pwm-bcm-iproc.o
diff --git a/drivers/pwm/pwm-axiado.c b/drivers/pwm/pwm-axiado.c
new file mode 100644
index 000000000000..4815d34b907e
--- /dev/null
+++ b/drivers/pwm/pwm-axiado.c
@@ -0,0 +1,310 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2021-2026 Axiado Corporation.
+ */
+
+/*
+ * Limitations:
+ * - Only normal polarity is supported.
+ * - Configuration changes take effect immediately; the current period is
+ *   not guaranteed to complete.
+ * - Disable operations take effect immediately; the current period is not
+ *   guaranteed to complete.
+ * - When disabled, the output remains high.
+ * - The supported period range is 2 through 0xfffffffe PWM input clock
+ *   cycles; 0xffffffff is reserved by the hardware for a constant-low
+ *   output. Longer periods are rounded down to the maximum.
+ * - The hardware interprets a zero high time as a constant high output, so
+ *   a 0% duty cycle is programmed as a constant-low period instead. That
+ *   encoding does not hold the requested period, so the period cannot be
+ *   read back from the hardware while the duty cycle is 0%.
+ * - A 100% duty cycle is supported and produces a constant high output.
+ */
+
+#include <linux/bits.h>
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/math64.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+
+/* Register offsets */
+#define AXIADO_PWM_CTRL_REG	0x0000
+#define AXIADO_PWM_PERIOD_REG	0x0004
+#define AXIADO_PWM_HIGH_REG	0x0008
+
+/* Period and duty cycle limits */
+#define AXIADO_PWM_PERIOD_MIN	2
+#define AXIADO_PWM_PERIOD_MAX	0xfffffffe
+#define AXIADO_PWM_PERIOD_CONST_LOW	0xffffffff
+#define AXIADO_PWM_DUTY_MIN	1
+
+/* Control register bits */
+#define AXIADO_PWM_CTRL_ENABLE	BIT(0)
+
+struct axiado_pwm_chip {
+	void __iomem *base;
+	unsigned long rate;
+	u32 cached_period;
+};
+
+struct axiado_pwm_waveform {
+	u32 period;
+	u32 duty;
+	bool enabled;
+};
+
+static int
+axiado_pwm_round_waveform_tohw(struct pwm_chip *chip,
+			       struct pwm_device *pwm,
+			       const struct pwm_waveform *wf,
+			       void *_wfhw)
+{
+	struct axiado_pwm_chip *axpwm = pwmchip_get_drvdata(chip);
+	struct axiado_pwm_waveform *wfhw = _wfhw;
+	u64 period;
+	u64 duty;
+	int ret = 0;
+
+	/* Encode a disabled request as a zeroed hardware waveform. */
+	if (!wf->period_length_ns) {
+		*wfhw = (struct axiado_pwm_waveform) {};
+
+		return 0;
+	}
+
+	/* Only an edge-aligned waveform starting at offset zero is supported. */
+	if (wf->duty_offset_ns)
+		return -EINVAL;
+
+	if (wf->duty_length_ns > wf->period_length_ns)
+		return -EINVAL;
+
+	period = mul_u64_u64_div_u64(wf->period_length_ns, axpwm->rate,
+				     NSEC_PER_SEC);
+
+	if (period < AXIADO_PWM_PERIOD_MIN) {
+		period = AXIADO_PWM_PERIOD_MIN;
+		ret = 1;
+	} else if (period > AXIADO_PWM_PERIOD_MAX) {
+		period = AXIADO_PWM_PERIOD_MAX;
+	}
+
+	/*
+	 * Keep the rounded period for a 0% duty cycle. .write_waveform()
+	 * translates it to the hardware constant-low representation.
+	 */
+	if (!wf->duty_length_ns) {
+		*wfhw = (struct axiado_pwm_waveform) {
+			.period = period,
+			.duty = 0,
+			.enabled = true,
+		};
+
+		return ret;
+	}
+
+	duty = mul_u64_u64_div_u64(wf->duty_length_ns, axpwm->rate,
+				   NSEC_PER_SEC);
+
+	/*
+	 * Preserve an exact 100% duty request when the hardware period has
+	 * been clamped.
+	 */
+	if (wf->duty_length_ns == wf->period_length_ns)
+		duty = period;
+
+	/*
+	 * Period clamping can leave the converted duty greater than the
+	 * final hardware period. In that case, clamp it to 100% duty.
+	 */
+	if (duty > period)
+		duty = period;
+
+	*wfhw = (struct axiado_pwm_waveform) {
+		.period = period,
+		.duty = duty,
+		.enabled = true,
+	};
+
+	return ret;
+}
+
+static int
+axiado_pwm_round_waveform_fromhw(struct pwm_chip *chip,
+				 struct pwm_device *pwm,
+				 const void *_wfhw,
+				 struct pwm_waveform *wf)
+{
+	struct axiado_pwm_chip *axpwm = pwmchip_get_drvdata(chip);
+	const struct axiado_pwm_waveform *wfhw = _wfhw;
+
+	if (!wfhw->enabled) {
+		*wf = (struct pwm_waveform) {
+			.period_length_ns = 0,
+			.duty_length_ns = 0,
+			.duty_offset_ns = 0,
+		};
+
+		return 0;
+	}
+
+	*wf = (struct pwm_waveform) {
+		.period_length_ns =
+			mul_u64_u64_div_u64_roundup(wfhw->period, NSEC_PER_SEC,
+						    axpwm->rate),
+		.duty_length_ns =
+			mul_u64_u64_div_u64_roundup(wfhw->duty, NSEC_PER_SEC,
+						    axpwm->rate),
+		.duty_offset_ns = 0,
+	};
+
+	return 0;
+}
+
+static int axiado_pwm_read_waveform(struct pwm_chip *chip,
+				    struct pwm_device *pwm,
+				    void *_wfhw)
+{
+	struct axiado_pwm_chip *axpwm = pwmchip_get_drvdata(chip);
+	struct axiado_pwm_waveform *wfhw = _wfhw;
+	u32 period;
+	u32 duty;
+	u32 ctrl;
+
+	ctrl = readl(axpwm->base + AXIADO_PWM_CTRL_REG);
+	period = readl(axpwm->base + AXIADO_PWM_PERIOD_REG);
+	duty = readl(axpwm->base + AXIADO_PWM_HIGH_REG);
+
+	/* The constant-low encoding doesn't hold the period, so restore it. */
+	if (period == AXIADO_PWM_PERIOD_CONST_LOW) {
+		period = axpwm->cached_period;
+		duty = 0;
+	} else if (duty > period) {
+		duty = period;
+	}
+
+	*wfhw = (struct axiado_pwm_waveform) {
+		.period = period,
+		.duty = duty,
+		.enabled = !!(ctrl & AXIADO_PWM_CTRL_ENABLE),
+	};
+
+	return 0;
+}
+
+static int axiado_pwm_write_waveform(struct pwm_chip *chip,
+				     struct pwm_device *pwm,
+				     const void *_wfhw)
+{
+	struct axiado_pwm_chip *axpwm = pwmchip_get_drvdata(chip);
+	const struct axiado_pwm_waveform *wfhw = _wfhw;
+	u32 period = wfhw->period;
+	u32 duty = wfhw->duty;
+
+	if (!wfhw->enabled) {
+		writel(0, axpwm->base + AXIADO_PWM_CTRL_REG);
+		return 0;
+	}
+
+	/*
+	 * A zero high time produces a constant high output, so use the
+	 * constant-low period encoding for a 0% duty cycle. Keep the high time
+	 * non-zero because a zero value takes precedence over that encoding.
+	 * Cache the requested period for .read_waveform().
+	 */
+	if (!duty) {
+		axpwm->cached_period = period;
+		period = AXIADO_PWM_PERIOD_CONST_LOW;
+		duty = AXIADO_PWM_DUTY_MIN;
+	}
+
+	/*
+	 * The hardware has no shadow registers. These writes may alter the
+	 * active waveform before the current period has completed.
+	 */
+	writel(period, axpwm->base + AXIADO_PWM_PERIOD_REG);
+	writel(duty, axpwm->base + AXIADO_PWM_HIGH_REG);
+	writel(AXIADO_PWM_CTRL_ENABLE, axpwm->base + AXIADO_PWM_CTRL_REG);
+
+	return 0;
+}
+
+static const struct pwm_ops axiado_pwm_ops = {
+	.sizeof_wfhw = sizeof(struct axiado_pwm_waveform),
+	.round_waveform_tohw = axiado_pwm_round_waveform_tohw,
+	.round_waveform_fromhw = axiado_pwm_round_waveform_fromhw,
+	.read_waveform = axiado_pwm_read_waveform,
+	.write_waveform = axiado_pwm_write_waveform,
+};
+
+static int axiado_pwm_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct axiado_pwm_chip *axpwm;
+	struct pwm_chip *chip;
+	struct clk *clk;
+	int ret;
+
+	chip = devm_pwmchip_alloc(dev, 1, sizeof(*axpwm));
+	if (IS_ERR(chip))
+		return PTR_ERR(chip);
+
+	axpwm = pwmchip_get_drvdata(chip);
+
+	axpwm->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(axpwm->base))
+		return dev_err_probe(dev, PTR_ERR(axpwm->base),
+				     "Failed to map registers\n");
+
+	clk = devm_clk_get_enabled(dev, NULL);
+	if (IS_ERR(clk))
+		return dev_err_probe(dev, PTR_ERR(clk),
+				     "Failed to get/enable clock\n");
+
+	ret = devm_clk_rate_exclusive_get(dev, clk);
+	if (ret)
+		return dev_err_probe(dev, ret,
+				     "Failed to lock clock rate\n");
+
+	axpwm->rate = clk_get_rate(clk);
+	if (!axpwm->rate)
+		return dev_err_probe(dev, -EINVAL,
+				     "Failed to get clock rate\n");
+
+	/*
+	 * Provide a valid fallback period if the bootloader left the
+	 * constant-low encoding programmed.
+	 */
+	axpwm->cached_period = AXIADO_PWM_PERIOD_MIN;
+
+	chip->ops = &axiado_pwm_ops;
+	chip->atomic = true;
+
+	ret = devm_pwmchip_add(dev, chip);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to add PWM chip\n");
+
+	return 0;
+}
+
+static const struct of_device_id axiado_pwm_match[] = {
+	{ .compatible = "axiado,ax3000-pwm" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, axiado_pwm_match);
+
+static struct platform_driver axiado_pwm_driver = {
+	.driver = {
+		.name =  "axiado-pwm",
+		.of_match_table = axiado_pwm_match,
+	},
+	.probe = axiado_pwm_probe,
+};
+module_platform_driver(axiado_pwm_driver);
+
+MODULE_AUTHOR("Axiado Corporation");
+MODULE_DESCRIPTION("Axiado PWM driver");
+MODULE_LICENSE("GPL");

-- 
2.34.1