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 * @chip: linux pwm chip representation
52 */
53 struct spear_pwm_chip {
54 void __iomem *mmio_base;
55 struct clk *clk;
56 struct pwm_chip chip;
57 };
58
to_spear_pwm_chip(struct pwm_chip * chip)59 static inline struct spear_pwm_chip *to_spear_pwm_chip(struct pwm_chip *chip)
60 {
61 return container_of(chip, struct spear_pwm_chip, chip);
62 }
63
spear_pwm_readl(struct spear_pwm_chip * chip,unsigned int num,unsigned long offset)64 static inline u32 spear_pwm_readl(struct spear_pwm_chip *chip, unsigned int num,
65 unsigned long offset)
66 {
67 return readl_relaxed(chip->mmio_base + (num << 4) + offset);
68 }
69
spear_pwm_writel(struct spear_pwm_chip * chip,unsigned int num,unsigned long offset,unsigned long val)70 static inline void spear_pwm_writel(struct spear_pwm_chip *chip,
71 unsigned int num, unsigned long offset,
72 unsigned long val)
73 {
74 writel_relaxed(val, chip->mmio_base + (num << 4) + offset);
75 }
76
spear_pwm_config(struct pwm_chip * chip,struct pwm_device * pwm,int duty_ns,int period_ns)77 static int spear_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
78 int duty_ns, int period_ns)
79 {
80 struct spear_pwm_chip *pc = to_spear_pwm_chip(chip);
81 u64 val, div, clk_rate;
82 unsigned long prescale = PWMCR_MIN_PRESCALE, pv, dc;
83 int ret;
84
85 /*
86 * Find pv, dc and prescale to suit duty_ns and period_ns. This is done
87 * according to formulas described below:
88 *
89 * period_ns = 10^9 * (PRESCALE + 1) * PV / PWM_CLK_RATE
90 * duty_ns = 10^9 * (PRESCALE + 1) * DC / PWM_CLK_RATE
91 *
92 * PV = (PWM_CLK_RATE * period_ns) / (10^9 * (PRESCALE + 1))
93 * DC = (PWM_CLK_RATE * duty_ns) / (10^9 * (PRESCALE + 1))
94 */
95 clk_rate = clk_get_rate(pc->clk);
96 while (1) {
97 div = 1000000000;
98 div *= 1 + prescale;
99 val = clk_rate * period_ns;
100 pv = div64_u64(val, div);
101 val = clk_rate * duty_ns;
102 dc = div64_u64(val, div);
103
104 /* if duty_ns and period_ns are not achievable then return */
105 if (pv < PWMPCR_MIN_PERIOD || dc < PWMDCR_MIN_DUTY)
106 return -EINVAL;
107
108 /*
109 * if pv and dc have crossed their upper limit, then increase
110 * prescale and recalculate pv and dc.
111 */
112 if (pv > PWMPCR_MAX_PERIOD || dc > PWMDCR_MAX_DUTY) {
113 if (++prescale > PWMCR_MAX_PRESCALE)
114 return -EINVAL;
115 continue;
116 }
117 break;
118 }
119
120 /*
121 * NOTE: the clock to PWM has to be enabled first before writing to the
122 * registers.
123 */
124 ret = clk_enable(pc->clk);
125 if (ret)
126 return ret;
127
128 spear_pwm_writel(pc, pwm->hwpwm, PWMCR,
129 prescale << PWMCR_PRESCALE_SHIFT);
130 spear_pwm_writel(pc, pwm->hwpwm, PWMDCR, dc);
131 spear_pwm_writel(pc, pwm->hwpwm, PWMPCR, pv);
132 clk_disable(pc->clk);
133
134 return 0;
135 }
136
spear_pwm_enable(struct pwm_chip * chip,struct pwm_device * pwm)137 static int spear_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
138 {
139 struct spear_pwm_chip *pc = to_spear_pwm_chip(chip);
140 int rc = 0;
141 u32 val;
142
143 rc = clk_enable(pc->clk);
144 if (rc)
145 return rc;
146
147 val = spear_pwm_readl(pc, pwm->hwpwm, PWMCR);
148 val |= PWMCR_PWM_ENABLE;
149 spear_pwm_writel(pc, pwm->hwpwm, PWMCR, val);
150
151 return 0;
152 }
153
spear_pwm_disable(struct pwm_chip * chip,struct pwm_device * pwm)154 static void spear_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
155 {
156 struct spear_pwm_chip *pc = to_spear_pwm_chip(chip);
157 u32 val;
158
159 val = spear_pwm_readl(pc, pwm->hwpwm, PWMCR);
160 val &= ~PWMCR_PWM_ENABLE;
161 spear_pwm_writel(pc, pwm->hwpwm, PWMCR, val);
162
163 clk_disable(pc->clk);
164 }
165
166 static const struct pwm_ops spear_pwm_ops = {
167 .config = spear_pwm_config,
168 .enable = spear_pwm_enable,
169 .disable = spear_pwm_disable,
170 .owner = THIS_MODULE,
171 };
172
spear_pwm_probe(struct platform_device * pdev)173 static int spear_pwm_probe(struct platform_device *pdev)
174 {
175 struct device_node *np = pdev->dev.of_node;
176 struct spear_pwm_chip *pc;
177 struct resource *r;
178 int ret;
179 u32 val;
180
181 pc = devm_kzalloc(&pdev->dev, sizeof(*pc), GFP_KERNEL);
182 if (!pc)
183 return -ENOMEM;
184
185 r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
186 pc->mmio_base = devm_ioremap_resource(&pdev->dev, r);
187 if (IS_ERR(pc->mmio_base))
188 return PTR_ERR(pc->mmio_base);
189
190 pc->clk = devm_clk_get(&pdev->dev, NULL);
191 if (IS_ERR(pc->clk))
192 return PTR_ERR(pc->clk);
193
194 platform_set_drvdata(pdev, pc);
195
196 pc->chip.dev = &pdev->dev;
197 pc->chip.ops = &spear_pwm_ops;
198 pc->chip.base = -1;
199 pc->chip.npwm = NUM_PWM;
200
201 ret = clk_prepare(pc->clk);
202 if (ret)
203 return ret;
204
205 if (of_device_is_compatible(np, "st,spear1340-pwm")) {
206 ret = clk_enable(pc->clk);
207 if (ret) {
208 clk_unprepare(pc->clk);
209 return ret;
210 }
211 /*
212 * Following enables PWM chip, channels would still be
213 * enabled individually through their control register
214 */
215 val = readl_relaxed(pc->mmio_base + PWMMCR);
216 val |= PWMMCR_PWM_ENABLE;
217 writel_relaxed(val, pc->mmio_base + PWMMCR);
218
219 clk_disable(pc->clk);
220 }
221
222 ret = pwmchip_add(&pc->chip);
223 if (ret < 0) {
224 clk_unprepare(pc->clk);
225 dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
226 }
227
228 return ret;
229 }
230
spear_pwm_remove(struct platform_device * pdev)231 static int spear_pwm_remove(struct platform_device *pdev)
232 {
233 struct spear_pwm_chip *pc = platform_get_drvdata(pdev);
234 int i;
235
236 for (i = 0; i < NUM_PWM; i++)
237 pwm_disable(&pc->chip.pwms[i]);
238
239 /* clk was prepared in probe, hence unprepare it here */
240 clk_unprepare(pc->clk);
241 return pwmchip_remove(&pc->chip);
242 }
243
244 static const struct of_device_id spear_pwm_of_match[] = {
245 { .compatible = "st,spear320-pwm" },
246 { .compatible = "st,spear1340-pwm" },
247 { }
248 };
249
250 MODULE_DEVICE_TABLE(of, spear_pwm_of_match);
251
252 static struct platform_driver spear_pwm_driver = {
253 .driver = {
254 .name = "spear-pwm",
255 .of_match_table = spear_pwm_of_match,
256 },
257 .probe = spear_pwm_probe,
258 .remove = spear_pwm_remove,
259 };
260
261 module_platform_driver(spear_pwm_driver);
262
263 MODULE_LICENSE("GPL");
264 MODULE_AUTHOR("Shiraz Hashim <shiraz.linux.kernel@gmail.com>");
265 MODULE_AUTHOR("Viresh Kumar <viresh.kumar@linaro.com>");
266 MODULE_ALIAS("platform:spear-pwm");
267