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/of_device.h>
18 #include <linux/platform_device.h>
19 #include <linux/pwm.h>
20 #include <linux/slab.h>
21
22 #define MX1_PWMC 0x00 /* PWM Control Register */
23 #define MX1_PWMS 0x04 /* PWM Sample Register */
24 #define MX1_PWMP 0x08 /* PWM Period Register */
25
26 #define MX1_PWMC_EN BIT(4)
27
28 struct pwm_imx1_chip {
29 struct clk *clk_ipg;
30 struct clk *clk_per;
31 void __iomem *mmio_base;
32 struct pwm_chip chip;
33 };
34
35 #define to_pwm_imx1_chip(chip) container_of(chip, struct pwm_imx1_chip, chip)
36
pwm_imx1_clk_prepare_enable(struct pwm_chip * chip)37 static int pwm_imx1_clk_prepare_enable(struct pwm_chip *chip)
38 {
39 struct pwm_imx1_chip *imx = to_pwm_imx1_chip(chip);
40 int ret;
41
42 ret = clk_prepare_enable(imx->clk_ipg);
43 if (ret)
44 return ret;
45
46 ret = clk_prepare_enable(imx->clk_per);
47 if (ret) {
48 clk_disable_unprepare(imx->clk_ipg);
49 return ret;
50 }
51
52 return 0;
53 }
54
pwm_imx1_clk_disable_unprepare(struct pwm_chip * chip)55 static void pwm_imx1_clk_disable_unprepare(struct pwm_chip *chip)
56 {
57 struct pwm_imx1_chip *imx = to_pwm_imx1_chip(chip);
58
59 clk_disable_unprepare(imx->clk_per);
60 clk_disable_unprepare(imx->clk_ipg);
61 }
62
pwm_imx1_config(struct pwm_chip * chip,struct pwm_device * pwm,int duty_ns,int period_ns)63 static int pwm_imx1_config(struct pwm_chip *chip,
64 struct pwm_device *pwm, int duty_ns, int period_ns)
65 {
66 struct pwm_imx1_chip *imx = to_pwm_imx1_chip(chip);
67 u32 max, p;
68
69 /*
70 * The PWM subsystem allows for exact frequencies. However,
71 * I cannot connect a scope on my device to the PWM line and
72 * thus cannot provide the program the PWM controller
73 * exactly. Instead, I'm relying on the fact that the
74 * Bootloader (u-boot or WinCE+haret) has programmed the PWM
75 * function group already. So I'll just modify the PWM sample
76 * register to follow the ratio of duty_ns vs. period_ns
77 * accordingly.
78 *
79 * This is good enough for programming the brightness of
80 * the LCD backlight.
81 *
82 * The real implementation would divide PERCLK[0] first by
83 * both the prescaler (/1 .. /128) and then by CLKSEL
84 * (/2 .. /16).
85 */
86 max = readl(imx->mmio_base + MX1_PWMP);
87 p = max * duty_ns / period_ns;
88
89 writel(max - p, imx->mmio_base + MX1_PWMS);
90
91 return 0;
92 }
93
pwm_imx1_enable(struct pwm_chip * chip,struct pwm_device * pwm)94 static int pwm_imx1_enable(struct pwm_chip *chip, struct pwm_device *pwm)
95 {
96 struct pwm_imx1_chip *imx = to_pwm_imx1_chip(chip);
97 u32 value;
98 int ret;
99
100 ret = pwm_imx1_clk_prepare_enable(chip);
101 if (ret < 0)
102 return ret;
103
104 value = readl(imx->mmio_base + MX1_PWMC);
105 value |= MX1_PWMC_EN;
106 writel(value, imx->mmio_base + MX1_PWMC);
107
108 return 0;
109 }
110
pwm_imx1_disable(struct pwm_chip * chip,struct pwm_device * pwm)111 static void pwm_imx1_disable(struct pwm_chip *chip, struct pwm_device *pwm)
112 {
113 struct pwm_imx1_chip *imx = to_pwm_imx1_chip(chip);
114 u32 value;
115
116 value = readl(imx->mmio_base + MX1_PWMC);
117 value &= ~MX1_PWMC_EN;
118 writel(value, imx->mmio_base + MX1_PWMC);
119
120 pwm_imx1_clk_disable_unprepare(chip);
121 }
122
123 static const struct pwm_ops pwm_imx1_ops = {
124 .enable = pwm_imx1_enable,
125 .disable = pwm_imx1_disable,
126 .config = pwm_imx1_config,
127 .owner = THIS_MODULE,
128 };
129
130 static const struct of_device_id pwm_imx1_dt_ids[] = {
131 { .compatible = "fsl,imx1-pwm", },
132 { /* sentinel */ }
133 };
134 MODULE_DEVICE_TABLE(of, pwm_imx1_dt_ids);
135
pwm_imx1_probe(struct platform_device * pdev)136 static int pwm_imx1_probe(struct platform_device *pdev)
137 {
138 struct pwm_imx1_chip *imx;
139
140 imx = devm_kzalloc(&pdev->dev, sizeof(*imx), GFP_KERNEL);
141 if (!imx)
142 return -ENOMEM;
143
144 platform_set_drvdata(pdev, imx);
145
146 imx->clk_ipg = devm_clk_get(&pdev->dev, "ipg");
147 if (IS_ERR(imx->clk_ipg))
148 return dev_err_probe(&pdev->dev, PTR_ERR(imx->clk_ipg),
149 "getting ipg clock failed\n");
150
151 imx->clk_per = devm_clk_get(&pdev->dev, "per");
152 if (IS_ERR(imx->clk_per))
153 return dev_err_probe(&pdev->dev, PTR_ERR(imx->clk_per),
154 "failed to get peripheral clock\n");
155
156 imx->chip.ops = &pwm_imx1_ops;
157 imx->chip.dev = &pdev->dev;
158 imx->chip.npwm = 1;
159
160 imx->mmio_base = devm_platform_ioremap_resource(pdev, 0);
161 if (IS_ERR(imx->mmio_base))
162 return PTR_ERR(imx->mmio_base);
163
164 return pwmchip_add(&imx->chip);
165 }
166
pwm_imx1_remove(struct platform_device * pdev)167 static int pwm_imx1_remove(struct platform_device *pdev)
168 {
169 struct pwm_imx1_chip *imx = platform_get_drvdata(pdev);
170
171 pwm_imx1_clk_disable_unprepare(&imx->chip);
172
173 return pwmchip_remove(&imx->chip);
174 }
175
176 static struct platform_driver pwm_imx1_driver = {
177 .driver = {
178 .name = "pwm-imx1",
179 .of_match_table = pwm_imx1_dt_ids,
180 },
181 .probe = pwm_imx1_probe,
182 .remove = pwm_imx1_remove,
183 };
184 module_platform_driver(pwm_imx1_driver);
185
186 MODULE_LICENSE("GPL v2");
187 MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>");
188