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  */
  52 struct spear_pwm_chip {
  53         void __iomem *mmio_base;
  54         struct clk *clk;
  55 };
  56
  57 static inline struct spear_pwm_chip *to_spear_pwm_chip(struct pwm_chip *chip)
  58 {
  59         return pwmchip_get_drvdata(chip);
  60 }
  61
  62 static 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
  68 static 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
  75 static 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(pc->clk);
  94         while (1) {
  95                 div = 1000000000;
  96                 div *= 1 + prescale;
  97                 val = clk_rate * period_ns;
  98                 pv = div64_u64(val, div);
  99                 val = clk_rate * duty_ns;
 100                 dc = div64_u64(val, 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(pc->clk);
 123         if (ret)
 124                 return ret;
 125
 126         spear_pwm_writel(pc, pwm->hwpwm, PWMCR,
 127                         prescale << PWMCR_PRESCALE_SHIFT);
 128         spear_pwm_writel(pc, pwm->hwpwm, PWMDCR, dc);
 129         spear_pwm_writel(pc, pwm->hwpwm, PWMPCR, pv);
 130         clk_disable(pc->clk);
 131
 132         return 0;
 133 }
 134
 135 static 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(pc->clk);
 142         if (rc)
 143                 return rc;
 144
 145         val = spear_pwm_readl(pc, pwm->hwpwm, PWMCR);
 146         val |= PWMCR_PWM_ENABLE;
 147         spear_pwm_writel(pc, pwm->hwpwm, PWMCR, val);
 148
 149         return 0;
 150 }
 151
 152 static 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(pc, pwm->hwpwm, PWMCR);
 158         val &= ~PWMCR_PWM_ENABLE;
 159         spear_pwm_writel(pc, pwm->hwpwm, PWMCR, val);
 160
 161         clk_disable(pc->clk);
 162 }
 163
 164 static 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, state->duty_cycle, 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
 188 static const struct pwm_ops spear_pwm_ops = {
 189         .apply = spear_pwm_apply,
 190 };
 191
 192 static 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(&pdev->dev, NUM_PWM, sizeof(*pc));
 201         if (IS_ERR(chip))
 202                 return PTR_ERR(chip);
 203         pc = to_spear_pwm_chip(chip);
 204
 205         pc->mmio_base = devm_platform_ioremap_resource(pdev, 0);
 206         if (IS_ERR(pc->mmio_base))
 207                 return PTR_ERR(pc->mmio_base);
 208
 209         pc->clk = devm_clk_get_prepared(&pdev->dev, NULL);
 210         if (IS_ERR(pc->clk))
 211                 return dev_err_probe(&pdev->dev, PTR_ERR(pc->clk),
 212                                      "Failed to get clock\n");
 213
 214         chip->ops = &spear_pwm_ops;
 215
 216         if (of_device_is_compatible(np, "st,spear1340-pwm")) {
 217                 ret = clk_enable(pc->clk);
 218                 if (ret)
 219                         return dev_err_probe(&pdev->dev, ret,
 220                                              "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(pc->clk);
 231         }
 232
 233         ret = devm_pwmchip_add(&pdev->dev, chip);
 234         if (ret < 0)
 235                 return dev_err_probe(&pdev->dev, ret, "pwmchip_add() failed\n");
 236
 237         return 0;
 238 }
 239
 240 static const struct of_device_id spear_pwm_of_match[] = {
 241         { .compatible = "st,spear320-pwm" },
 242         { .compatible = "st,spear1340-pwm" },
 243         { }
 244 };
 245
 246 MODULE_DEVICE_TABLE(of, spear_pwm_of_match);
 247
 248 static 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
 256 module_platform_driver(spear_pwm_driver);
 257
 258 MODULE_DESCRIPTION("ST Microelectronics SPEAr Pulse Width Modulator driver");
 259 MODULE_LICENSE("GPL");
 260 MODULE_AUTHOR("Shiraz Hashim <shiraz.linux.kernel@gmail.com>");
 261 MODULE_AUTHOR("Viresh Kumar <viresh.kumar@linaro.com>");
 262 MODULE_ALIAS("platform:spear-pwm");