xref: /linux/drivers/pwm/pwm-imx1.c (revision a1ff5a7d78a036d6c2178ee5acd6ba4946243800)
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 
27 struct pwm_imx1_chip {
28 	struct clk *clk_ipg;
29 	struct clk *clk_per;
30 	void __iomem *mmio_base;
31 };
32 
to_pwm_imx1_chip(struct pwm_chip * chip)33 static inline struct pwm_imx1_chip *to_pwm_imx1_chip(struct pwm_chip *chip)
34 {
35 	return pwmchip_get_drvdata(chip);
36 }
37 
pwm_imx1_clk_prepare_enable(struct pwm_chip * chip)38 static 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 
pwm_imx1_clk_disable_unprepare(struct pwm_chip * chip)56 static 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 
pwm_imx1_config(struct pwm_chip * chip,struct pwm_device * pwm,u64 duty_ns,u64 period_ns)64 static 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 
pwm_imx1_enable(struct pwm_chip * chip,struct pwm_device * pwm)95 static 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 
pwm_imx1_disable(struct pwm_chip * chip,struct pwm_device * pwm)112 static 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 
pwm_imx1_apply(struct pwm_chip * chip,struct pwm_device * pwm,const struct pwm_state * state)124 static 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 
149 static const struct pwm_ops pwm_imx1_ops = {
150 	.apply = pwm_imx1_apply,
151 };
152 
153 static const struct of_device_id pwm_imx1_dt_ids[] = {
154 	{ .compatible = "fsl,imx1-pwm", },
155 	{ /* sentinel */ }
156 };
157 MODULE_DEVICE_TABLE(of, pwm_imx1_dt_ids);
158 
pwm_imx1_probe(struct platform_device * pdev)159 static 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 
188 static 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 };
195 module_platform_driver(pwm_imx1_driver);
196 
197 MODULE_DESCRIPTION("i.MX1 and i.MX21 Pulse Width Modulator driver");
198 MODULE_LICENSE("GPL v2");
199 MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>");
200