drivers/pwm/pwm-spear.c

   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
  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
  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
  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
  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
 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
 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
 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
 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                 .owner = THIS_MODULE,
 256                 .of_match_table = spear_pwm_of_match,
 257         },
 258         .probe = spear_pwm_probe,
 259         .remove = spear_pwm_remove,
 260 };
 261
 262 module_platform_driver(spear_pwm_driver);
 263
 264 MODULE_LICENSE("GPL");
 265 MODULE_AUTHOR("Shiraz Hashim <shiraz.linux.kernel@gmail.com>");
 266 MODULE_AUTHOR("Viresh Kumar <viresh.kumar@linaro.com>");
 267 MODULE_ALIAS("platform:spear-pwm");