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 struct pwm_chip chip;
32};
33
34#define to_pwm_imx1_chip(chip) container_of(chip, struct pwm_imx1_chip, chip)
35
36static 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(clk: imx->clk_ipg);
42 if (ret)
43 return ret;
44
45 ret = clk_prepare_enable(clk: imx->clk_per);
46 if (ret) {
47 clk_disable_unprepare(clk: imx->clk_ipg);
48 return ret;
49 }
50
51 return 0;
52}
53
54static 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(clk: imx->clk_per);
59 clk_disable_unprepare(clk: imx->clk_ipg);
60}
61
62static 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(addr: imx->mmio_base + MX1_PWMP);
86 p = mul_u64_u64_div_u64(a: max, mul: duty_ns, div: period_ns);
87
88 writel(val: max - p, addr: imx->mmio_base + MX1_PWMS);
89
90 return 0;
91}
92
93static 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(addr: imx->mmio_base + MX1_PWMC);
104 value |= MX1_PWMC_EN;
105 writel(val: value, addr: imx->mmio_base + MX1_PWMC);
106
107 return 0;
108}
109
110static 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(addr: imx->mmio_base + MX1_PWMC);
116 value &= ~MX1_PWMC_EN;
117 writel(val: value, addr: imx->mmio_base + MX1_PWMC);
118
119 pwm_imx1_clk_disable_unprepare(chip);
120}
121
122static 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, duty_ns: state->duty_cycle, period_ns: 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
147static const struct pwm_ops pwm_imx1_ops = {
148 .apply = pwm_imx1_apply,
149 .owner = THIS_MODULE,
150};
151
152static const struct of_device_id pwm_imx1_dt_ids[] = {
153 { .compatible = "fsl,imx1-pwm", },
154 { /* sentinel */ }
155};
156MODULE_DEVICE_TABLE(of, pwm_imx1_dt_ids);
157
158static int pwm_imx1_probe(struct platform_device *pdev)
159{
160 struct pwm_imx1_chip *imx;
161
162 imx = devm_kzalloc(dev: &pdev->dev, size: sizeof(*imx), GFP_KERNEL);
163 if (!imx)
164 return -ENOMEM;
165
166 imx->clk_ipg = devm_clk_get(dev: &pdev->dev, id: "ipg");
167 if (IS_ERR(ptr: imx->clk_ipg))
168 return dev_err_probe(dev: &pdev->dev, err: PTR_ERR(ptr: imx->clk_ipg),
169 fmt: "getting ipg clock failed\n");
170
171 imx->clk_per = devm_clk_get(dev: &pdev->dev, id: "per");
172 if (IS_ERR(ptr: imx->clk_per))
173 return dev_err_probe(dev: &pdev->dev, err: PTR_ERR(ptr: imx->clk_per),
174 fmt: "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, index: 0);
181 if (IS_ERR(ptr: imx->mmio_base))
182 return PTR_ERR(ptr: imx->mmio_base);
183
184 return devm_pwmchip_add(dev: &pdev->dev, chip: &imx->chip);
185}
186
187static 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};
194module_platform_driver(pwm_imx1_driver);
195
196MODULE_LICENSE("GPL v2");
197MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>");
198

source code of linux/drivers/pwm/pwm-imx1.c