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.hashim@st.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  * @dev: pointer to device structure of pwm chip
  53  */
  54 struct spear_pwm_chip {
  55         void __iomem *mmio_base;
  56         struct clk *clk;
  57         struct pwm_chip chip;
  58         struct device *dev;
  59 };
  60
  61 static inline struct spear_pwm_chip *to_spear_pwm_chip(struct pwm_chip *chip)
  62 {
  63         return container_of(chip, struct spear_pwm_chip, chip);
  64 }
  65
  66 static inline u32 spear_pwm_readl(struct spear_pwm_chip *chip, unsigned int num,
  67                                   unsigned long offset)
  68 {
  69         return readl_relaxed(chip->mmio_base + (num << 4) + offset);
  70 }
  71
  72 static inline void spear_pwm_writel(struct spear_pwm_chip *chip,
  73                                     unsigned int num, unsigned long offset,
  74                                     unsigned long val)
  75 {
  76         writel_relaxed(val, chip->mmio_base + (num << 4) + offset);
  77 }
  78
  79 static int spear_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
  80                             int duty_ns, int period_ns)
  81 {
  82         struct spear_pwm_chip *pc = to_spear_pwm_chip(chip);
  83         u64 val, div, clk_rate;
  84         unsigned long prescale = PWMCR_MIN_PRESCALE, pv, dc;
  85         int ret;
  86
  87         /*
  88          * Find pv, dc and prescale to suit duty_ns and period_ns. This is done
  89          * according to formulas described below:
  90          *
  91          * period_ns = 10^9 * (PRESCALE + 1) * PV / PWM_CLK_RATE
  92          * duty_ns = 10^9 * (PRESCALE + 1) * DC / PWM_CLK_RATE
  93          *
  94          * PV = (PWM_CLK_RATE * period_ns) / (10^9 * (PRESCALE + 1))
  95          * DC = (PWM_CLK_RATE * duty_ns) / (10^9 * (PRESCALE + 1))
  96          */
  97         clk_rate = clk_get_rate(pc->clk);
  98         while (1) {
  99                 div = 1000000000;
 100                 div *= 1 + prescale;
 101                 val = clk_rate * period_ns;
 102                 pv = div64_u64(val, div);
 103                 val = clk_rate * duty_ns;
 104                 dc = div64_u64(val, div);
 105
 106                 /* if duty_ns and period_ns are not achievable then return */
 107                 if (pv < PWMPCR_MIN_PERIOD || dc < PWMDCR_MIN_DUTY)
 108                         return -EINVAL;
 109
 110                 /*
 111                  * if pv and dc have crossed their upper limit, then increase
 112                  * prescale and recalculate pv and dc.
 113                  */
 114                 if (pv > PWMPCR_MAX_PERIOD || dc > PWMDCR_MAX_DUTY) {
 115                         if (++prescale > PWMCR_MAX_PRESCALE)
 116                                 return -EINVAL;
 117                         continue;
 118                 }
 119                 break;
 120         }
 121
 122         /*
 123          * NOTE: the clock to PWM has to be enabled first before writing to the
 124          * registers.
 125          */
 126         ret = clk_enable(pc->clk);
 127         if (ret)
 128                 return ret;
 129
 130         spear_pwm_writel(pc, pwm->hwpwm, PWMCR,
 131                         prescale << PWMCR_PRESCALE_SHIFT);
 132         spear_pwm_writel(pc, pwm->hwpwm, PWMDCR, dc);
 133         spear_pwm_writel(pc, pwm->hwpwm, PWMPCR, pv);
 134         clk_disable(pc->clk);
 135
 136         return 0;
 137 }
 138
 139 static int spear_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
 140 {
 141         struct spear_pwm_chip *pc = to_spear_pwm_chip(chip);
 142         int rc = 0;
 143         u32 val;
 144
 145         rc = clk_enable(pc->clk);
 146         if (!rc)
 147                 return rc;
 148
 149         val = spear_pwm_readl(pc, pwm->hwpwm, PWMCR);
 150         val |= PWMCR_PWM_ENABLE;
 151         spear_pwm_writel(pc, pwm->hwpwm, PWMCR, val);
 152
 153         return 0;
 154 }
 155
 156 static void spear_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
 157 {
 158         struct spear_pwm_chip *pc = to_spear_pwm_chip(chip);
 159         u32 val;
 160
 161         val = spear_pwm_readl(pc, pwm->hwpwm, PWMCR);
 162         val &= ~PWMCR_PWM_ENABLE;
 163         spear_pwm_writel(pc, pwm->hwpwm, PWMCR, val);
 164
 165         clk_disable(pc->clk);
 166 }
 167
 168 static const struct pwm_ops spear_pwm_ops = {
 169         .config = spear_pwm_config,
 170         .enable = spear_pwm_enable,
 171         .disable = spear_pwm_disable,
 172         .owner = THIS_MODULE,
 173 };
 174
 175 static int spear_pwm_probe(struct platform_device *pdev)
 176 {
 177         struct device_node *np = pdev->dev.of_node;
 178         struct spear_pwm_chip *pc;
 179         struct resource *r;
 180         int ret;
 181         u32 val;
 182
 183         r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 184         if (!r) {
 185                 dev_err(&pdev->dev, "no memory resources defined\n");
 186                 return -ENODEV;
 187         }
 188
 189         pc = devm_kzalloc(&pdev->dev, sizeof(*pc), GFP_KERNEL);
 190         if (!pc) {
 191                 dev_err(&pdev->dev, "failed to allocate memory\n");
 192                 return -ENOMEM;
 193         }
 194
 195         pc->mmio_base = devm_ioremap_resource(&pdev->dev, r);
 196         if (IS_ERR(pc->mmio_base))
 197                 return PTR_ERR(pc->mmio_base);
 198
 199         pc->clk = devm_clk_get(&pdev->dev, NULL);
 200         if (IS_ERR(pc->clk))
 201                 return PTR_ERR(pc->clk);
 202
 203         pc->dev = &pdev->dev;
 204         platform_set_drvdata(pdev, pc);
 205
 206         pc->chip.dev = &pdev->dev;
 207         pc->chip.ops = &spear_pwm_ops;
 208         pc->chip.base = -1;
 209         pc->chip.npwm = NUM_PWM;
 210
 211         ret = clk_prepare(pc->clk);
 212         if (!ret)
 213                 return ret;
 214
 215         if (of_device_is_compatible(np, "st,spear1340-pwm")) {
 216                 ret = clk_enable(pc->clk);
 217                 if (!ret) {
 218                         clk_unprepare(pc->clk);
 219                         return ret;
 220                 }
 221                 /*
 222                  * Following enables PWM chip, channels would still be
 223                  * enabled individually through their control register
 224                  */
 225                 val = readl_relaxed(pc->mmio_base + PWMMCR);
 226                 val |= PWMMCR_PWM_ENABLE;
 227                 writel_relaxed(val, pc->mmio_base + PWMMCR);
 228
 229                 clk_disable(pc->clk);
 230         }
 231
 232         ret = pwmchip_add(&pc->chip);
 233         if (!ret) {
 234                 clk_unprepare(pc->clk);
 235                 dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
 236         }
 237
 238         return ret;
 239 }
 240
 241 static int spear_pwm_remove(struct platform_device *pdev)
 242 {
 243         struct spear_pwm_chip *pc = platform_get_drvdata(pdev);
 244         int i;
 245
 246         for (i = 0; i < NUM_PWM; i++)
 247                 pwm_disable(&pc->chip.pwms[i]);
 248
 249         /* clk was prepared in probe, hence unprepare it here */
 250         clk_unprepare(pc->clk);
 251         return pwmchip_remove(&pc->chip);
 252 }
 253
 254 static struct of_device_id spear_pwm_of_match[] = {
 255         { .compatible = "st,spear320-pwm" },
 256         { .compatible = "st,spear1340-pwm" },
 257         { }
 258 };
 259
 260 MODULE_DEVICE_TABLE(of, spear_pwm_of_match);
 261
 262 static struct platform_driver spear_pwm_driver = {
 263         .driver = {
 264                 .name = "spear-pwm",
 265                 .of_match_table = spear_pwm_of_match,
 266         },
 267         .probe = spear_pwm_probe,
 268         .remove = spear_pwm_remove,
 269 };
 270
 271 module_platform_driver(spear_pwm_driver);
 272
 273 MODULE_LICENSE("GPL");
 274 MODULE_AUTHOR("Shiraz Hashim <shiraz.hashim@st.com>");
 275 MODULE_AUTHOR("Viresh Kumar <viresh.kumar@linaro.com>");
 276 MODULE_ALIAS("platform:spear-pwm");