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