pwm: Add Apple PWM controller

Adds the Apple PWM controller driver.
Signed-off-by: Sasha Finkelstein <fnkl.kernel@gmail.com>
Acked-by: Sven Peter <sven@svenpeter.dev>
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>

drivers/pwm/Kconfig

@@ -51,6 +51,18 @@ config PWM_AB8500
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-ab8500.
 
+config PWM_APPLE
+	tristate "Apple SoC PWM support"
+	depends on ARCH_APPLE || COMPILE_TEST
+	help
+	  Generic PWM framework driver for PWM controller present on
+	  Apple SoCs
+
+	  Say Y here if you have an ARM Apple laptop, otherwise say N
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pwm-apple.
+
 config PWM_ATMEL
 	tristate "Atmel PWM support"
 	depends on ARCH_AT91 || COMPILE_TEST

drivers/pwm/Makefile

@@ -2,6 +2,7 @@
 obj-$(CONFIG_PWM)		+= core.o
 obj-$(CONFIG_PWM_SYSFS)		+= sysfs.o
 obj-$(CONFIG_PWM_AB8500)	+= pwm-ab8500.o
+obj-$(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

drivers/pwm/pwm-apple.c

+// SPDX-License-Identifier: GPL-2.0 OR MIT
+/*
+ * Driver for the Apple SoC PWM controller
+ *
+ * Copyright The Asahi Linux Contributors
+ *
+ * Limitations:
+ * - The writes to cycle registers are shadowed until a write to
+ *   the control register.
+ * - If both OFF_CYCLES and ON_CYCLES are set to 0, the output
+ *   is a constant off signal.
+ * - When APPLE_PWM_CTRL is set to 0, the output is constant low
+ */
+
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+#include <linux/io.h>
+#include <linux/clk.h>
+#include <linux/math64.h>
+
+#define APPLE_PWM_CTRL        0x00
+#define APPLE_PWM_ON_CYCLES   0x1c
+#define APPLE_PWM_OFF_CYCLES  0x18
+
+#define APPLE_PWM_CTRL_ENABLE        BIT(0)
+#define APPLE_PWM_CTRL_MODE          BIT(2)
+#define APPLE_PWM_CTRL_UPDATE        BIT(5)
+#define APPLE_PWM_CTRL_TRIGGER       BIT(9)
+#define APPLE_PWM_CTRL_INVERT        BIT(10)
+#define APPLE_PWM_CTRL_OUTPUT_ENABLE BIT(14)
+
+struct apple_pwm {
+	struct pwm_chip chip;
+	void __iomem *base;
+	u64 clkrate;
+};
+
+static inline struct apple_pwm *to_apple_pwm(struct pwm_chip *chip)
+{
+	return container_of(chip, struct apple_pwm, chip);
+}
+
+static int apple_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			   const struct pwm_state *state)
+{
+	struct apple_pwm *fpwm;
+
+	if (state->polarity == PWM_POLARITY_INVERSED)
+		return -EINVAL;
+
+	fpwm = to_apple_pwm(chip);
+	if (state->enabled) {
+		u64 on_cycles, off_cycles;
+
+		on_cycles = mul_u64_u64_div_u64(fpwm->clkrate,
+						state->duty_cycle, NSEC_PER_SEC);
+		if (on_cycles > 0xFFFFFFFF)
+			on_cycles = 0xFFFFFFFF;
+
+		off_cycles = mul_u64_u64_div_u64(fpwm->clkrate,
+						 state->period, NSEC_PER_SEC) - on_cycles;
+		if (off_cycles > 0xFFFFFFFF)
+			off_cycles = 0xFFFFFFFF;
+
+		writel(on_cycles, fpwm->base + APPLE_PWM_ON_CYCLES);
+		writel(off_cycles, fpwm->base + APPLE_PWM_OFF_CYCLES);
+		writel(APPLE_PWM_CTRL_ENABLE | APPLE_PWM_CTRL_OUTPUT_ENABLE | APPLE_PWM_CTRL_UPDATE,
+		       fpwm->base + APPLE_PWM_CTRL);
+	} else {
+		writel(0, fpwm->base + APPLE_PWM_CTRL);
+	}
+	return 0;
+}
+
+static int apple_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
+			   struct pwm_state *state)
+{
+	struct apple_pwm *fpwm;
+	u32 on_cycles, off_cycles, ctrl;
+
+	fpwm = to_apple_pwm(chip);
+
+	ctrl = readl(fpwm->base + APPLE_PWM_CTRL);
+	on_cycles = readl(fpwm->base + APPLE_PWM_ON_CYCLES);
+	off_cycles = readl(fpwm->base + APPLE_PWM_OFF_CYCLES);
+
+	state->enabled = (ctrl & APPLE_PWM_CTRL_ENABLE) && (ctrl & APPLE_PWM_CTRL_OUTPUT_ENABLE);
+	state->polarity = PWM_POLARITY_NORMAL;
+	// on_cycles + off_cycles is 33 bits, NSEC_PER_SEC is 30, there is no overflow
+	state->duty_cycle = DIV64_U64_ROUND_UP((u64)on_cycles * NSEC_PER_SEC, fpwm->clkrate);
+	state->period = DIV64_U64_ROUND_UP(((u64)off_cycles + (u64)on_cycles) *
+					    NSEC_PER_SEC, fpwm->clkrate);
+
+	return 0;
+}
+
+static const struct pwm_ops apple_pwm_ops = {
+	.apply = apple_pwm_apply,
+	.get_state = apple_pwm_get_state,
+	.owner = THIS_MODULE,
+};
+
+static int apple_pwm_probe(struct platform_device *pdev)
+{
+	struct apple_pwm *fpwm;
+	struct clk *clk;
+	int ret;
+
+	fpwm = devm_kzalloc(&pdev->dev, sizeof(*fpwm), GFP_KERNEL);
+	if (!fpwm)
+		return -ENOMEM;
+
+	fpwm->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(fpwm->base))
+		return PTR_ERR(fpwm->base);
+
+	clk = devm_clk_get_enabled(&pdev->dev, NULL);
+	if (IS_ERR(clk))
+		return dev_err_probe(&pdev->dev, PTR_ERR(clk), "unable to get the clock");
+
+	/*
+	 * Uses the 24MHz system clock on all existing devices, can only
+	 * happen if the device tree is broken
+	 *
+	 * This check is done to prevent an overflow in .apply
+	 */
+	fpwm->clkrate = clk_get_rate(clk);
+	if (fpwm->clkrate > NSEC_PER_SEC)
+		return dev_err_probe(&pdev->dev, -EINVAL, "pwm clock out of range");
+
+	fpwm->chip.dev = &pdev->dev;
+	fpwm->chip.npwm = 1;
+	fpwm->chip.ops = &apple_pwm_ops;
+
+	ret = devm_pwmchip_add(&pdev->dev, &fpwm->chip);
+	if (ret < 0)
+		return dev_err_probe(&pdev->dev, ret, "unable to add pwm chip");
+
+	return 0;
+}
+
+static const struct of_device_id apple_pwm_of_match[] = {
+	{ .compatible = "apple,s5l-fpwm" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, apple_pwm_of_match);
+
+static struct platform_driver apple_pwm_driver = {
+	.probe = apple_pwm_probe,
+	.driver = {
+		.name = "apple-pwm",
+		.of_match_table = apple_pwm_of_match,
+	},
+};
+module_platform_driver(apple_pwm_driver);
+
+MODULE_DESCRIPTION("Apple SoC PWM driver");
+MODULE_LICENSE("Dual MIT/GPL");