linux/drivers/pwm/pwm-spear.c
<<
>>
Prefs
   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 */
  53struct spear_pwm_chip {
  54        void __iomem *mmio_base;
  55        struct clk *clk;
  56        struct pwm_chip chip;
  57};
  58
  59static 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
  64static 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
  70static 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
  77static 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
 137static 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
 154static 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
 166static 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
 173static 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                dev_err(&pdev->dev, "failed to allocate memory\n");
 184                return -ENOMEM;
 185        }
 186
 187        r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 188        pc->mmio_base = devm_ioremap_resource(&pdev->dev, r);
 189        if (IS_ERR(pc->mmio_base))
 190                return PTR_ERR(pc->mmio_base);
 191
 192        pc->clk = devm_clk_get(&pdev->dev, NULL);
 193        if (IS_ERR(pc->clk))
 194                return PTR_ERR(pc->clk);
 195
 196        platform_set_drvdata(pdev, pc);
 197
 198        pc->chip.dev = &pdev->dev;
 199        pc->chip.ops = &spear_pwm_ops;
 200        pc->chip.base = -1;
 201        pc->chip.npwm = NUM_PWM;
 202
 203        ret = clk_prepare(pc->clk);
 204        if (ret)
 205                return ret;
 206
 207        if (of_device_is_compatible(np, "st,spear1340-pwm")) {
 208                ret = clk_enable(pc->clk);
 209                if (ret) {
 210                        clk_unprepare(pc->clk);
 211                        return ret;
 212                }
 213                /*
 214                 * Following enables PWM chip, channels would still be
 215                 * enabled individually through their control register
 216                 */
 217                val = readl_relaxed(pc->mmio_base + PWMMCR);
 218                val |= PWMMCR_PWM_ENABLE;
 219                writel_relaxed(val, pc->mmio_base + PWMMCR);
 220
 221                clk_disable(pc->clk);
 222        }
 223
 224        ret = pwmchip_add(&pc->chip);
 225        if (!ret) {
 226                clk_unprepare(pc->clk);
 227                dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
 228        }
 229
 230        return ret;
 231}
 232
 233static int spear_pwm_remove(struct platform_device *pdev)
 234{
 235        struct spear_pwm_chip *pc = platform_get_drvdata(pdev);
 236        int i;
 237
 238        for (i = 0; i < NUM_PWM; i++)
 239                pwm_disable(&pc->chip.pwms[i]);
 240
 241        /* clk was prepared in probe, hence unprepare it here */
 242        clk_unprepare(pc->clk);
 243        return pwmchip_remove(&pc->chip);
 244}
 245
 246static const struct of_device_id spear_pwm_of_match[] = {
 247        { .compatible = "st,spear320-pwm" },
 248        { .compatible = "st,spear1340-pwm" },
 249        { }
 250};
 251
 252MODULE_DEVICE_TABLE(of, spear_pwm_of_match);
 253
 254static struct platform_driver spear_pwm_driver = {
 255        .driver = {
 256                .name = "spear-pwm",
 257                .owner = THIS_MODULE,
 258                .of_match_table = spear_pwm_of_match,
 259        },
 260        .probe = spear_pwm_probe,
 261        .remove = spear_pwm_remove,
 262};
 263
 264module_platform_driver(spear_pwm_driver);
 265
 266MODULE_LICENSE("GPL");
 267MODULE_AUTHOR("Shiraz Hashim <shiraz.hashim@st.com>");
 268MODULE_AUTHOR("Viresh Kumar <viresh.kumar@linaro.com>");
 269MODULE_ALIAS("platform:spear-pwm");
 270
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.