1// SPDX-License-Identifier: GPL-2.0
2/*
3 * simple driver for PWM (Pulse Width Modulator) controller
4 *
5 * Derived from pxa PWM driver by eric miao <eric.miao@marvell.com>
6 */
7
8#include <linux/bitfield.h>
9#include <linux/bitops.h>
10#include <linux/clk.h>
11#include <linux/delay.h>
12#include <linux/err.h>
13#include <linux/io.h>
14#include <linux/kernel.h>
15#include <linux/module.h>
16#include <linux/of.h>
17#include <linux/platform_device.h>
18#include <linux/pwm.h>
19#include <linux/slab.h>
20
21#define MX1_PWMC			0x00   /* PWM Control Register */
22#define MX1_PWMS			0x04   /* PWM Sample Register */
23#define MX1_PWMP			0x08   /* PWM Period Register */
24
25#define MX1_PWMC_EN			BIT(4)
26
27struct pwm_imx1_chip {
28	struct clk *clk_ipg;
29	struct clk *clk_per;
30	void __iomem *mmio_base;
31};
32
33static inline struct pwm_imx1_chip *to_pwm_imx1_chip(struct pwm_chip *chip)
34{
35	return pwmchip_get_drvdata(chip);
36}
37
38static int pwm_imx1_clk_prepare_enable(struct pwm_chip *chip)
39{
40	struct pwm_imx1_chip *imx = to_pwm_imx1_chip(chip);
41	int ret;
42
43	ret = clk_prepare_enable(imx->clk_ipg);
44	if (ret)
45		return ret;
46
47	ret = clk_prepare_enable(imx->clk_per);
48	if (ret) {
49		clk_disable_unprepare(imx->clk_ipg);
50		return ret;
51	}
52
53	return 0;
54}
55
56static void pwm_imx1_clk_disable_unprepare(struct pwm_chip *chip)
57{
58	struct pwm_imx1_chip *imx = to_pwm_imx1_chip(chip);
59
60	clk_disable_unprepare(imx->clk_per);
61	clk_disable_unprepare(imx->clk_ipg);
62}
63
64static int pwm_imx1_config(struct pwm_chip *chip,
65			   struct pwm_device *pwm, u64 duty_ns, u64 period_ns)
66{
67	struct pwm_imx1_chip *imx = to_pwm_imx1_chip(chip);
68	u32 max, p;
69
70	/*
71	 * The PWM subsystem allows for exact frequencies. However,
72	 * I cannot connect a scope on my device to the PWM line and
73	 * thus cannot provide the program the PWM controller
74	 * exactly. Instead, I'm relying on the fact that the
75	 * Bootloader (u-boot or WinCE+haret) has programmed the PWM
76	 * function group already. So I'll just modify the PWM sample
77	 * register to follow the ratio of duty_ns vs. period_ns
78	 * accordingly.
79	 *
80	 * This is good enough for programming the brightness of
81	 * the LCD backlight.
82	 *
83	 * The real implementation would divide PERCLK[0] first by
84	 * both the prescaler (/1 .. /128) and then by CLKSEL
85	 * (/2 .. /16).
86	 */
87	max = readl(imx->mmio_base + MX1_PWMP);
88	p = mul_u64_u64_div_u64(max, duty_ns, period_ns);
89
90	writel(max - p, imx->mmio_base + MX1_PWMS);
91
92	return 0;
93}
94
95static int pwm_imx1_enable(struct pwm_chip *chip, struct pwm_device *pwm)
96{
97	struct pwm_imx1_chip *imx = to_pwm_imx1_chip(chip);
98	u32 value;
99	int ret;
100
101	ret = pwm_imx1_clk_prepare_enable(chip);
102	if (ret < 0)
103		return ret;
104
105	value = readl(imx->mmio_base + MX1_PWMC);
106	value |= MX1_PWMC_EN;
107	writel(value, imx->mmio_base + MX1_PWMC);
108
109	return 0;
110}
111
112static void pwm_imx1_disable(struct pwm_chip *chip, struct pwm_device *pwm)
113{
114	struct pwm_imx1_chip *imx = to_pwm_imx1_chip(chip);
115	u32 value;
116
117	value = readl(imx->mmio_base + MX1_PWMC);
118	value &= ~MX1_PWMC_EN;
119	writel(value, imx->mmio_base + MX1_PWMC);
120
121	pwm_imx1_clk_disable_unprepare(chip);
122}
123
124static int pwm_imx1_apply(struct pwm_chip *chip, struct pwm_device *pwm,
125			  const struct pwm_state *state)
126{
127	int err;
128
129	if (state->polarity != PWM_POLARITY_NORMAL)
130		return -EINVAL;
131
132	if (!state->enabled) {
133		if (pwm->state.enabled)
134			pwm_imx1_disable(chip, pwm);
135
136		return 0;
137	}
138
139	err = pwm_imx1_config(chip, pwm, state->duty_cycle, state->period);
140	if (err)
141		return err;
142
143	if (!pwm->state.enabled)
144		return pwm_imx1_enable(chip, pwm);
145
146	return 0;
147}
148
149static const struct pwm_ops pwm_imx1_ops = {
150	.apply = pwm_imx1_apply,
151};
152
153static const struct of_device_id pwm_imx1_dt_ids[] = {
154	{ .compatible = "fsl,imx1-pwm", },
155	{ /* sentinel */ }
156};
157MODULE_DEVICE_TABLE(of, pwm_imx1_dt_ids);
158
159static int pwm_imx1_probe(struct platform_device *pdev)
160{
161	struct pwm_chip *chip;
162	struct pwm_imx1_chip *imx;
163
164	chip = devm_pwmchip_alloc(&pdev->dev, 1, sizeof(*imx));
165	if (IS_ERR(chip))
166		return PTR_ERR(chip);
167	imx = to_pwm_imx1_chip(chip);
168
169	imx->clk_ipg = devm_clk_get(&pdev->dev, "ipg");
170	if (IS_ERR(imx->clk_ipg))
171		return dev_err_probe(&pdev->dev, PTR_ERR(imx->clk_ipg),
172				     "getting ipg clock failed\n");
173
174	imx->clk_per = devm_clk_get(&pdev->dev, "per");
175	if (IS_ERR(imx->clk_per))
176		return dev_err_probe(&pdev->dev, PTR_ERR(imx->clk_per),
177				     "failed to get peripheral clock\n");
178
179	chip->ops = &pwm_imx1_ops;
180
181	imx->mmio_base = devm_platform_ioremap_resource(pdev, 0);
182	if (IS_ERR(imx->mmio_base))
183		return PTR_ERR(imx->mmio_base);
184
185	return devm_pwmchip_add(&pdev->dev, chip);
186}
187
188static struct platform_driver pwm_imx1_driver = {
189	.driver = {
190		.name = "pwm-imx1",
191		.of_match_table = pwm_imx1_dt_ids,
192	},
193	.probe = pwm_imx1_probe,
194};
195module_platform_driver(pwm_imx1_driver);
196
197MODULE_LICENSE("GPL v2");
198MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>");
199