pwm: Add driver for AXI PWM generator

Add support for the Analog Devices AXI PWM Generator. This device is an
FPGA-implemented peripheral used as PWM signal generator and can be
interfaced with AXI4. The register map of this peripheral makes it
possible to configure the period and duty cycle of the output signal.

Link: https://analogdevicesinc.github.io/hdl/library/axi_pwm_gen/index.html
Co-developed-by: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@analog.com>
Co-developed-by: David Lechner <dlechner@baylibre.com>
Signed-off-by: David Lechner <dlechner@baylibre.com>
Signed-off-by: Drew Fustini <dfustini@baylibre.com>
Acked-by: Nuno Sa <nuno.sa@analog.com>
Co-developed-by: Trevor Gamblin <tgamblin@baylibre.com>
Signed-off-by: Trevor Gamblin <tgamblin@baylibre.com>
Link: https://lore.kernel.org/r/20240605203507.1934434-3-tgamblin@baylibre.com
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>

MAINTAINERS

@@ -3578,6 +3578,7 @@ L:	linux-pwm@vger.kernel.org
 S:	Supported
 W:	https://ez.analog.com/linux-software-drivers
 F:	Documentation/devicetree/bindings/pwm/adi,axi-pwmgen.yaml
+F:	drivers/pwm/pwm-axi-pwmgen.c
 
 AXXIA I2C CONTROLLER
 M:	Krzysztof Adamski <krzysztof.adamski@nokia.com>

drivers/pwm/Kconfig

@@ -94,6 +94,19 @@ config PWM_ATMEL_TCB
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-atmel-tcb.
 
+config PWM_AXI_PWMGEN
+	tristate "Analog Devices AXI PWM generator"
+	depends on MICROBLAZE || NIOS2 || ARCH_ZYNQ || ARCH_ZYNQMP || ARCH_INTEL_SOCFPGA || COMPILE_TEST
+	select REGMAP_MMIO
+	help
+	  This enables support for the Analog Devices AXI PWM generator.
+
+	  This is a configurable PWM generator with variable pulse width and
+	  period.
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called pwm-axi-pwmgen.
+
 config PWM_BCM_IPROC
 	tristate "iProc PWM support"
 	depends on ARCH_BCM_IPROC || COMPILE_TEST

drivers/pwm/Makefile

@@ -5,6 +5,7 @@ obj-$(CONFIG_PWM_APPLE)		+= pwm-apple.o
 obj-$(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-$(CONFIG_PWM_AXI_PWMGEN)	+= pwm-axi-pwmgen.o
 obj-$(CONFIG_PWM_BCM_IPROC)	+= pwm-bcm-iproc.o
 obj-$(CONFIG_PWM_BCM_KONA)	+= pwm-bcm-kona.o
 obj-$(CONFIG_PWM_BCM2835)	+= pwm-bcm2835.o

drivers/pwm/pwm-axi-pwmgen.c

@@ -0,0 +1,241 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Analog Devices AXI PWM generator
+ *
+ * Copyright 2024 Analog Devices Inc.
+ * Copyright 2024 Baylibre SAS
+ *
+ * Device docs: https://analogdevicesinc.github.io/hdl/library/axi_pwm_gen/index.html
+ *
+ * Limitations:
+ * - The writes to registers for period and duty are shadowed until
+ *   LOAD_CONFIG is written to AXI_PWMGEN_REG_CONFIG, at which point
+ *   they take effect.
+ * - Writing LOAD_CONFIG also has the effect of re-synchronizing all
+ *   enabled channels, which could cause glitching on other channels. It
+ *   is therefore expected that channels are assigned harmonic periods
+ *   and all have a single user coordinating this.
+ * - Supports normal polarity. Does not support changing polarity.
+ * - On disable, the PWM output becomes low (inactive).
+ */
+#include <linux/bits.h>
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/fpga/adi-axi-common.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+
+#define AXI_PWMGEN_REG_CORE_VERSION	0x00
+#define AXI_PWMGEN_REG_ID		0x04
+#define AXI_PWMGEN_REG_SCRATCHPAD	0x08
+#define AXI_PWMGEN_REG_CORE_MAGIC	0x0C
+#define AXI_PWMGEN_REG_CONFIG		0x10
+#define AXI_PWMGEN_REG_NPWM		0x14
+#define AXI_PWMGEN_CHX_PERIOD(ch)	(0x40 + (4 * (ch)))
+#define AXI_PWMGEN_CHX_DUTY(ch)		(0x80 + (4 * (ch)))
+#define AXI_PWMGEN_CHX_OFFSET(ch)	(0xC0 + (4 * (ch)))
+#define AXI_PWMGEN_REG_CORE_MAGIC_VAL	0x601A3471 /* Identification number to test during setup */
+#define AXI_PWMGEN_LOAD_CONFIG		BIT(1)
+#define AXI_PWMGEN_REG_CONFIG_RESET	BIT(0)
+
+struct axi_pwmgen_ddata {
+	struct regmap *regmap;
+	unsigned long clk_rate_hz;
+};
+
+static const struct regmap_config axi_pwmgen_regmap_config = {
+	.reg_bits = 32,
+	.reg_stride = 4,
+	.val_bits = 32,
+};
+
+static int axi_pwmgen_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			    const struct pwm_state *state)
+{
+	struct axi_pwmgen_ddata *ddata = pwmchip_get_drvdata(chip);
+	unsigned int ch = pwm->hwpwm;
+	struct regmap *regmap = ddata->regmap;
+	u64 period_cnt, duty_cnt;
+	int ret;
+
+	if (state->polarity != PWM_POLARITY_NORMAL)
+		return -EINVAL;
+
+	if (state->enabled) {
+		period_cnt = mul_u64_u64_div_u64(state->period, ddata->clk_rate_hz, NSEC_PER_SEC);
+		if (period_cnt > UINT_MAX)
+			period_cnt = UINT_MAX;
+
+		if (period_cnt == 0)
+			return -EINVAL;
+
+		ret = regmap_write(regmap, AXI_PWMGEN_CHX_PERIOD(ch), period_cnt);
+		if (ret)
+			return ret;
+
+		duty_cnt = mul_u64_u64_div_u64(state->duty_cycle, ddata->clk_rate_hz, NSEC_PER_SEC);
+		if (duty_cnt > UINT_MAX)
+			duty_cnt = UINT_MAX;
+
+		ret = regmap_write(regmap, AXI_PWMGEN_CHX_DUTY(ch), duty_cnt);
+		if (ret)
+			return ret;
+	} else {
+		ret = regmap_write(regmap, AXI_PWMGEN_CHX_PERIOD(ch), 0);
+		if (ret)
+			return ret;
+
+		ret = regmap_write(regmap, AXI_PWMGEN_CHX_DUTY(ch), 0);
+		if (ret)
+			return ret;
+	}
+
+	return regmap_write(regmap, AXI_PWMGEN_REG_CONFIG, AXI_PWMGEN_LOAD_CONFIG);
+}
+
+static int axi_pwmgen_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
+				struct pwm_state *state)
+{
+	struct axi_pwmgen_ddata *ddata = pwmchip_get_drvdata(chip);
+	struct regmap *regmap = ddata->regmap;
+	unsigned int ch = pwm->hwpwm;
+	u32 cnt;
+	int ret;
+
+	ret = regmap_read(regmap, AXI_PWMGEN_CHX_PERIOD(ch), &cnt);
+	if (ret)
+		return ret;
+
+	state->enabled = cnt != 0;
+
+	state->period = DIV_ROUND_UP_ULL((u64)cnt * NSEC_PER_SEC, ddata->clk_rate_hz);
+
+	ret = regmap_read(regmap, AXI_PWMGEN_CHX_DUTY(ch), &cnt);
+	if (ret)
+		return ret;
+
+	state->duty_cycle = DIV_ROUND_UP_ULL((u64)cnt * NSEC_PER_SEC, ddata->clk_rate_hz);
+
+	state->polarity = PWM_POLARITY_NORMAL;
+
+	return 0;
+}
+
+static const struct pwm_ops axi_pwmgen_pwm_ops = {
+	.apply = axi_pwmgen_apply,
+	.get_state = axi_pwmgen_get_state,
+};
+
+static int axi_pwmgen_setup(struct regmap *regmap, struct device *dev)
+{
+	int ret;
+	u32 val;
+
+	ret = regmap_read(regmap, AXI_PWMGEN_REG_CORE_MAGIC, &val);
+	if (ret)
+		return ret;
+
+	if (val != AXI_PWMGEN_REG_CORE_MAGIC_VAL)
+		return dev_err_probe(dev, -ENODEV,
+			"failed to read expected value from register: got %08x, expected %08x\n",
+			val, AXI_PWMGEN_REG_CORE_MAGIC_VAL);
+
+	ret = regmap_read(regmap, AXI_PWMGEN_REG_CORE_VERSION, &val);
+	if (ret)
+		return ret;
+
+	if (ADI_AXI_PCORE_VER_MAJOR(val) != 2) {
+		return dev_err_probe(dev, -ENODEV, "Unsupported peripheral version %u.%u.%u\n",
+			ADI_AXI_PCORE_VER_MAJOR(val),
+			ADI_AXI_PCORE_VER_MINOR(val),
+			ADI_AXI_PCORE_VER_PATCH(val));
+	}
+
+	/* Enable the core */
+	ret = regmap_update_bits(regmap, AXI_PWMGEN_REG_CONFIG, AXI_PWMGEN_REG_CONFIG_RESET, 0);
+	if (ret)
+		return ret;
+
+	ret = regmap_read(regmap, AXI_PWMGEN_REG_NPWM, &val);
+	if (ret)
+		return ret;
+
+	/* Return the number of PWMs */
+	return val;
+}
+
+static int axi_pwmgen_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct regmap *regmap;
+	struct pwm_chip *chip;
+	struct axi_pwmgen_ddata *ddata;
+	struct clk *clk;
+	void __iomem *io_base;
+	int ret;
+
+	io_base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(io_base))
+		return PTR_ERR(io_base);
+
+	regmap = devm_regmap_init_mmio(dev, io_base, &axi_pwmgen_regmap_config);
+	if (IS_ERR(regmap))
+		return dev_err_probe(dev, PTR_ERR(regmap),
+				     "failed to init register map\n");
+
+	ret = axi_pwmgen_setup(regmap, dev);
+	if (ret < 0)
+		return ret;
+
+	chip = devm_pwmchip_alloc(dev, ret, sizeof(*ddata));
+	if (IS_ERR(chip))
+		return PTR_ERR(chip);
+	ddata = pwmchip_get_drvdata(chip);
+	ddata->regmap = regmap;
+
+	clk = devm_clk_get_enabled(dev, NULL);
+	if (IS_ERR(clk))
+		return dev_err_probe(dev, PTR_ERR(clk), "failed to get clock\n");
+
+	ret = devm_clk_rate_exclusive_get(dev, clk);
+	if (ret)
+		return dev_err_probe(dev, ret, "failed to get exclusive rate\n");
+
+	ddata->clk_rate_hz = clk_get_rate(clk);
+	if (!ddata->clk_rate_hz || ddata->clk_rate_hz > NSEC_PER_SEC)
+		return dev_err_probe(dev, -EINVAL,
+				     "Invalid clock rate: %lu\n", ddata->clk_rate_hz);
+
+	chip->ops = &axi_pwmgen_pwm_ops;
+	chip->atomic = true;
+
+	ret = devm_pwmchip_add(dev, chip);
+	if (ret)
+		return dev_err_probe(dev, ret, "could not add PWM chip\n");
+
+	return 0;
+}
+
+static const struct of_device_id axi_pwmgen_ids[] = {
+	{ .compatible = "adi,axi-pwmgen-2.00.a" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, axi_pwmgen_ids);
+
+static struct platform_driver axi_pwmgen_driver = {
+	.driver = {
+		.name = "axi-pwmgen",
+		.of_match_table = axi_pwmgen_ids,
+	},
+	.probe = axi_pwmgen_probe,
+};
+module_platform_driver(axi_pwmgen_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Sergiu Cuciurean <sergiu.cuciurean@analog.com>");
+MODULE_AUTHOR("Trevor Gamblin <tgamblin@baylibre.com>");
+MODULE_DESCRIPTION("Driver for the Analog Devices AXI PWM generator");