1// SPDX-License-Identifier: GPL-2.0 OR MIT
  2/*
  3 * Driver for the Apple SoC PWM controller
  4 *
  5 * Copyright The Asahi Linux Contributors
  6 *
  7 * Limitations:
  8 * - The writes to cycle registers are shadowed until a write to
  9 *   the control register.
 10 * - If both OFF_CYCLES and ON_CYCLES are set to 0, the output
 11 *   is a constant off signal.
 12 * - When APPLE_PWM_CTRL is set to 0, the output is constant low
 13 */
 14
 15#include <linux/mod_devicetable.h>
 16#include <linux/module.h>
 17#include <linux/platform_device.h>
 18#include <linux/pwm.h>
 19#include <linux/io.h>
 20#include <linux/clk.h>
 21#include <linux/math64.h>
 22
 23#define APPLE_PWM_CTRL        0x00
 24#define APPLE_PWM_ON_CYCLES   0x1c
 25#define APPLE_PWM_OFF_CYCLES  0x18
 26
 27#define APPLE_PWM_CTRL_ENABLE        BIT(0)
 28#define APPLE_PWM_CTRL_MODE          BIT(2)
 29#define APPLE_PWM_CTRL_UPDATE        BIT(5)
 30#define APPLE_PWM_CTRL_TRIGGER       BIT(9)
 31#define APPLE_PWM_CTRL_INVERT        BIT(10)
 32#define APPLE_PWM_CTRL_OUTPUT_ENABLE BIT(14)
 33
 34struct apple_pwm {
 35	void __iomem *base;
 36	u64 clkrate;
 37};
 38
 39static inline struct apple_pwm *to_apple_pwm(struct pwm_chip *chip)
 40{
 41	return pwmchip_get_drvdata(chip);
 42}
 43
 44static int apple_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 45			   const struct pwm_state *state)
 46{
 47	struct apple_pwm *fpwm;
 48
 49	if (state->polarity == PWM_POLARITY_INVERSED)
 50		return -EINVAL;
 51
 52	fpwm = to_apple_pwm(chip);
 53	if (state->enabled) {
 54		u64 on_cycles, off_cycles;
 55
 56		on_cycles = mul_u64_u64_div_u64(fpwm->clkrate,
 57						state->duty_cycle, NSEC_PER_SEC);
 58		if (on_cycles > 0xFFFFFFFF)
 59			on_cycles = 0xFFFFFFFF;
 60
 61		off_cycles = mul_u64_u64_div_u64(fpwm->clkrate,
 62						 state->period, NSEC_PER_SEC) - on_cycles;
 63		if (off_cycles > 0xFFFFFFFF)
 64			off_cycles = 0xFFFFFFFF;
 65
 66		writel(on_cycles, fpwm->base + APPLE_PWM_ON_CYCLES);
 67		writel(off_cycles, fpwm->base + APPLE_PWM_OFF_CYCLES);
 68		writel(APPLE_PWM_CTRL_ENABLE | APPLE_PWM_CTRL_OUTPUT_ENABLE | APPLE_PWM_CTRL_UPDATE,
 69		       fpwm->base + APPLE_PWM_CTRL);
 70	} else {
 71		writel(0, fpwm->base + APPLE_PWM_CTRL);
 72	}
 73	return 0;
 74}
 75
 76static int apple_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
 77			   struct pwm_state *state)
 78{
 79	struct apple_pwm *fpwm;
 80	u32 on_cycles, off_cycles, ctrl;
 81
 82	fpwm = to_apple_pwm(chip);
 83
 84	ctrl = readl(fpwm->base + APPLE_PWM_CTRL);
 85	on_cycles = readl(fpwm->base + APPLE_PWM_ON_CYCLES);
 86	off_cycles = readl(fpwm->base + APPLE_PWM_OFF_CYCLES);
 87
 88	state->enabled = (ctrl & APPLE_PWM_CTRL_ENABLE) && (ctrl & APPLE_PWM_CTRL_OUTPUT_ENABLE);
 89	state->polarity = PWM_POLARITY_NORMAL;
 90	// on_cycles + off_cycles is 33 bits, NSEC_PER_SEC is 30, there is no overflow
 91	state->duty_cycle = DIV64_U64_ROUND_UP((u64)on_cycles * NSEC_PER_SEC, fpwm->clkrate);
 92	state->period = DIV64_U64_ROUND_UP(((u64)off_cycles + (u64)on_cycles) *
 93					    NSEC_PER_SEC, fpwm->clkrate);
 94
 95	return 0;
 96}
 97
 98static const struct pwm_ops apple_pwm_ops = {
 99	.apply = apple_pwm_apply,
100	.get_state = apple_pwm_get_state,
101};
102
103static int apple_pwm_probe(struct platform_device *pdev)
104{
105	struct pwm_chip *chip;
106	struct apple_pwm *fpwm;
107	struct clk *clk;
108	int ret;
109
110	chip = devm_pwmchip_alloc(&pdev->dev, 1, sizeof(*fpwm));
111	if (IS_ERR(chip))
112		return PTR_ERR(chip);
113
114	fpwm = to_apple_pwm(chip);
115
116	fpwm->base = devm_platform_ioremap_resource(pdev, 0);
117	if (IS_ERR(fpwm->base))
118		return PTR_ERR(fpwm->base);
119
120	clk = devm_clk_get_enabled(&pdev->dev, NULL);
121	if (IS_ERR(clk))
122		return dev_err_probe(&pdev->dev, PTR_ERR(clk), "unable to get the clock");
123
124	/*
125	 * Uses the 24MHz system clock on all existing devices, can only
126	 * happen if the device tree is broken
127	 *
128	 * This check is done to prevent an overflow in .apply
129	 */
130	fpwm->clkrate = clk_get_rate(clk);
131	if (fpwm->clkrate > NSEC_PER_SEC)
132		return dev_err_probe(&pdev->dev, -EINVAL, "pwm clock out of range");
133
134	chip->ops = &apple_pwm_ops;
135
136	ret = devm_pwmchip_add(&pdev->dev, chip);
137	if (ret < 0)
138		return dev_err_probe(&pdev->dev, ret, "unable to add pwm chip");
139
140	return 0;
141}
142
143static const struct of_device_id apple_pwm_of_match[] = {
144	{ .compatible = "apple,s5l-fpwm" },
145	{}
146};
147MODULE_DEVICE_TABLE(of, apple_pwm_of_match);
148
149static struct platform_driver apple_pwm_driver = {
150	.probe = apple_pwm_probe,
151	.driver = {
152		.name = "apple-pwm",
153		.of_match_table = apple_pwm_of_match,
154	},
155};
156module_platform_driver(apple_pwm_driver);
157
158MODULE_DESCRIPTION("Apple SoC PWM driver");
159MODULE_LICENSE("Dual MIT/GPL");