1/*
2 * ST Microelectronics SPEAr Pulse Width Modulator driver
3 *
4 * Copyright (C) 2012 ST Microelectronics
5 * Shiraz Hashim <shiraz.linux.kernel@gmail.com>
6 *
7 * This file is licensed under the terms of the GNU General Public
8 * License version 2. This program is licensed "as is" without any
9 * warranty of any kind, whether express or implied.
10 */
11
12#include <linux/clk.h>
13#include <linux/err.h>
14#include <linux/io.h>
15#include <linux/ioport.h>
16#include <linux/kernel.h>
17#include <linux/math64.h>
18#include <linux/module.h>
19#include <linux/of.h>
20#include <linux/platform_device.h>
21#include <linux/pwm.h>
22#include <linux/slab.h>
23#include <linux/types.h>
24
25#define NUM_PWM 4
26
27/* PWM registers and bits definitions */
28#define PWMCR 0x00 /* Control Register */
29#define PWMCR_PWM_ENABLE 0x1
30#define PWMCR_PRESCALE_SHIFT 2
31#define PWMCR_MIN_PRESCALE 0x00
32#define PWMCR_MAX_PRESCALE 0x3FFF
33
34#define PWMDCR 0x04 /* Duty Cycle Register */
35#define PWMDCR_MIN_DUTY 0x0001
36#define PWMDCR_MAX_DUTY 0xFFFF
37
38#define PWMPCR 0x08 /* Period Register */
39#define PWMPCR_MIN_PERIOD 0x0001
40#define PWMPCR_MAX_PERIOD 0xFFFF
41
42/* Following only available on 13xx SoCs */
43#define PWMMCR 0x3C /* Master Control Register */
44#define PWMMCR_PWM_ENABLE 0x1
45
46/**
47 * struct spear_pwm_chip - struct representing pwm chip
48 *
49 * @mmio_base: base address of pwm chip
50 * @clk: pointer to clk structure of pwm chip
51 */
52struct spear_pwm_chip {
53 void __iomem *mmio_base;
54 struct clk *clk;
55};
56
57static inline struct spear_pwm_chip *to_spear_pwm_chip(struct pwm_chip *chip)
58{
59 return pwmchip_get_drvdata(chip);
60}
61
62static inline u32 spear_pwm_readl(struct spear_pwm_chip *chip, unsigned int num,
63 unsigned long offset)
64{
65 return readl_relaxed(chip->mmio_base + (num << 4) + offset);
66}
67
68static inline void spear_pwm_writel(struct spear_pwm_chip *chip,
69 unsigned int num, unsigned long offset,
70 unsigned long val)
71{
72 writel_relaxed(val, chip->mmio_base + (num << 4) + offset);
73}
74
75static int spear_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
76 u64 duty_ns, u64 period_ns)
77{
78 struct spear_pwm_chip *pc = to_spear_pwm_chip(chip);
79 u64 val, div, clk_rate;
80 unsigned long prescale = PWMCR_MIN_PRESCALE, pv, dc;
81 int ret;
82
83 /*
84 * Find pv, dc and prescale to suit duty_ns and period_ns. This is done
85 * according to formulas described below:
86 *
87 * period_ns = 10^9 * (PRESCALE + 1) * PV / PWM_CLK_RATE
88 * duty_ns = 10^9 * (PRESCALE + 1) * DC / PWM_CLK_RATE
89 *
90 * PV = (PWM_CLK_RATE * period_ns) / (10^9 * (PRESCALE + 1))
91 * DC = (PWM_CLK_RATE * duty_ns) / (10^9 * (PRESCALE + 1))
92 */
93 clk_rate = clk_get_rate(clk: pc->clk);
94 while (1) {
95 div = 1000000000;
96 div *= 1 + prescale;
97 val = clk_rate * period_ns;
98 pv = div64_u64(dividend: val, divisor: div);
99 val = clk_rate * duty_ns;
100 dc = div64_u64(dividend: val, divisor: div);
101
102 /* if duty_ns and period_ns are not achievable then return */
103 if (pv < PWMPCR_MIN_PERIOD || dc < PWMDCR_MIN_DUTY)
104 return -EINVAL;
105
106 /*
107 * if pv and dc have crossed their upper limit, then increase
108 * prescale and recalculate pv and dc.
109 */
110 if (pv > PWMPCR_MAX_PERIOD || dc > PWMDCR_MAX_DUTY) {
111 if (++prescale > PWMCR_MAX_PRESCALE)
112 return -EINVAL;
113 continue;
114 }
115 break;
116 }
117
118 /*
119 * NOTE: the clock to PWM has to be enabled first before writing to the
120 * registers.
121 */
122 ret = clk_enable(clk: pc->clk);
123 if (ret)
124 return ret;
125
126 spear_pwm_writel(chip: pc, num: pwm->hwpwm, PWMCR,
127 val: prescale << PWMCR_PRESCALE_SHIFT);
128 spear_pwm_writel(chip: pc, num: pwm->hwpwm, PWMDCR, val: dc);
129 spear_pwm_writel(chip: pc, num: pwm->hwpwm, PWMPCR, val: pv);
130 clk_disable(clk: pc->clk);
131
132 return 0;
133}
134
135static int spear_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
136{
137 struct spear_pwm_chip *pc = to_spear_pwm_chip(chip);
138 int rc = 0;
139 u32 val;
140
141 rc = clk_enable(clk: pc->clk);
142 if (rc)
143 return rc;
144
145 val = spear_pwm_readl(chip: pc, num: pwm->hwpwm, PWMCR);
146 val |= PWMCR_PWM_ENABLE;
147 spear_pwm_writel(chip: pc, num: pwm->hwpwm, PWMCR, val);
148
149 return 0;
150}
151
152static void spear_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
153{
154 struct spear_pwm_chip *pc = to_spear_pwm_chip(chip);
155 u32 val;
156
157 val = spear_pwm_readl(chip: pc, num: pwm->hwpwm, PWMCR);
158 val &= ~PWMCR_PWM_ENABLE;
159 spear_pwm_writel(chip: pc, num: pwm->hwpwm, PWMCR, val);
160
161 clk_disable(clk: pc->clk);
162}
163
164static int spear_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
165 const struct pwm_state *state)
166{
167 int err;
168
169 if (state->polarity != PWM_POLARITY_NORMAL)
170 return -EINVAL;
171
172 if (!state->enabled) {
173 if (pwm->state.enabled)
174 spear_pwm_disable(chip, pwm);
175 return 0;
176 }
177
178 err = spear_pwm_config(chip, pwm, duty_ns: state->duty_cycle, period_ns: state->period);
179 if (err)
180 return err;
181
182 if (!pwm->state.enabled)
183 return spear_pwm_enable(chip, pwm);
184
185 return 0;
186}
187
188static const struct pwm_ops spear_pwm_ops = {
189 .apply = spear_pwm_apply,
190};
191
192static int spear_pwm_probe(struct platform_device *pdev)
193{
194 struct device_node *np = pdev->dev.of_node;
195 struct pwm_chip *chip;
196 struct spear_pwm_chip *pc;
197 int ret;
198 u32 val;
199
200 chip = devm_pwmchip_alloc(parent: &pdev->dev, NUM_PWM, sizeof_priv: sizeof(*pc));
201 if (IS_ERR(ptr: chip))
202 return PTR_ERR(ptr: chip);
203 pc = to_spear_pwm_chip(chip);
204
205 pc->mmio_base = devm_platform_ioremap_resource(pdev, index: 0);
206 if (IS_ERR(ptr: pc->mmio_base))
207 return PTR_ERR(ptr: pc->mmio_base);
208
209 pc->clk = devm_clk_get_prepared(dev: &pdev->dev, NULL);
210 if (IS_ERR(ptr: pc->clk))
211 return dev_err_probe(dev: &pdev->dev, err: PTR_ERR(ptr: pc->clk),
212 fmt: "Failed to get clock\n");
213
214 chip->ops = &spear_pwm_ops;
215
216 if (of_device_is_compatible(device: np, "st,spear1340-pwm")) {
217 ret = clk_enable(clk: pc->clk);
218 if (ret)
219 return dev_err_probe(dev: &pdev->dev, err: ret,
220 fmt: "Failed to enable clk\n");
221
222 /*
223 * Following enables PWM chip, channels would still be
224 * enabled individually through their control register
225 */
226 val = readl_relaxed(pc->mmio_base + PWMMCR);
227 val |= PWMMCR_PWM_ENABLE;
228 writel_relaxed(val, pc->mmio_base + PWMMCR);
229
230 clk_disable(clk: pc->clk);
231 }
232
233 ret = devm_pwmchip_add(&pdev->dev, chip);
234 if (ret < 0)
235 return dev_err_probe(dev: &pdev->dev, err: ret, fmt: "pwmchip_add() failed\n");
236
237 return 0;
238}
239
240static const struct of_device_id spear_pwm_of_match[] = {
241 { .compatible = "st,spear320-pwm" },
242 { .compatible = "st,spear1340-pwm" },
243 { }
244};
245
246MODULE_DEVICE_TABLE(of, spear_pwm_of_match);
247
248static struct platform_driver spear_pwm_driver = {
249 .driver = {
250 .name = "spear-pwm",
251 .of_match_table = spear_pwm_of_match,
252 },
253 .probe = spear_pwm_probe,
254};
255
256module_platform_driver(spear_pwm_driver);
257
258MODULE_DESCRIPTION("ST Microelectronics SPEAr Pulse Width Modulator driver");
259MODULE_LICENSE("GPL");
260MODULE_AUTHOR("Shiraz Hashim <shiraz.linux.kernel@gmail.com>");
261MODULE_AUTHOR("Viresh Kumar <viresh.kumar@linaro.com>");
262MODULE_ALIAS("platform:spear-pwm");
263

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