linux/drivers/pwm/pwm-pxa.c
<<
>>
Prefs
   1/*
   2 * drivers/pwm/pwm-pxa.c
   3 *
   4 * simple driver for PWM (Pulse Width Modulator) controller
   5 *
   6 * This program is free software; you can redistribute it and/or modify
   7 * it under the terms of the GNU General Public License version 2 as
   8 * published by the Free Software Foundation.
   9 *
  10 * 2008-02-13   initial version
  11 *              eric miao <eric.miao@marvell.com>
  12 */
  13
  14#include <linux/module.h>
  15#include <linux/kernel.h>
  16#include <linux/platform_device.h>
  17#include <linux/slab.h>
  18#include <linux/err.h>
  19#include <linux/clk.h>
  20#include <linux/io.h>
  21#include <linux/pwm.h>
  22
  23#include <asm/div64.h>
  24
  25#define HAS_SECONDARY_PWM       0x10
  26#define PWM_ID_BASE(d)          ((d) & 0xf)
  27
  28static const struct platform_device_id pwm_id_table[] = {
  29        /*   PWM    has_secondary_pwm? */
  30        { "pxa25x-pwm", 0 },
  31        { "pxa27x-pwm", 0 | HAS_SECONDARY_PWM },
  32        { "pxa168-pwm", 1 },
  33        { "pxa910-pwm", 1 },
  34        { },
  35};
  36MODULE_DEVICE_TABLE(platform, pwm_id_table);
  37
  38/* PWM registers and bits definitions */
  39#define PWMCR           (0x00)
  40#define PWMDCR          (0x04)
  41#define PWMPCR          (0x08)
  42
  43#define PWMCR_SD        (1 << 6)
  44#define PWMDCR_FD       (1 << 10)
  45
  46struct pxa_pwm_chip {
  47        struct pwm_chip chip;
  48        struct device   *dev;
  49
  50        struct clk      *clk;
  51        int             clk_enabled;
  52        void __iomem    *mmio_base;
  53};
  54
  55static inline struct pxa_pwm_chip *to_pxa_pwm_chip(struct pwm_chip *chip)
  56{
  57        return container_of(chip, struct pxa_pwm_chip, chip);
  58}
  59
  60/*
  61 * period_ns = 10^9 * (PRESCALE + 1) * (PV + 1) / PWM_CLK_RATE
  62 * duty_ns   = 10^9 * (PRESCALE + 1) * DC / PWM_CLK_RATE
  63 */
  64static int pxa_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
  65                          int duty_ns, int period_ns)
  66{
  67        struct pxa_pwm_chip *pc = to_pxa_pwm_chip(chip);
  68        unsigned long long c;
  69        unsigned long period_cycles, prescale, pv, dc;
  70        unsigned long offset;
  71        int rc;
  72
  73        offset = pwm->hwpwm ? 0x10 : 0;
  74
  75        c = clk_get_rate(pc->clk);
  76        c = c * period_ns;
  77        do_div(c, 1000000000);
  78        period_cycles = c;
  79
  80        if (period_cycles < 1)
  81                period_cycles = 1;
  82        prescale = (period_cycles - 1) / 1024;
  83        pv = period_cycles / (prescale + 1) - 1;
  84
  85        if (prescale > 63)
  86                return -EINVAL;
  87
  88        if (duty_ns == period_ns)
  89                dc = PWMDCR_FD;
  90        else
  91                dc = (pv + 1) * duty_ns / period_ns;
  92
  93        /* NOTE: the clock to PWM has to be enabled first
  94         * before writing to the registers
  95         */
  96        rc = clk_prepare_enable(pc->clk);
  97        if (rc < 0)
  98                return rc;
  99
 100        writel(prescale, pc->mmio_base + offset + PWMCR);
 101        writel(dc, pc->mmio_base + offset + PWMDCR);
 102        writel(pv, pc->mmio_base + offset + PWMPCR);
 103
 104        clk_disable_unprepare(pc->clk);
 105        return 0;
 106}
 107
 108static int pxa_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
 109{
 110        struct pxa_pwm_chip *pc = to_pxa_pwm_chip(chip);
 111        int rc = 0;
 112
 113        if (!pc->clk_enabled) {
 114                rc = clk_prepare_enable(pc->clk);
 115                if (!rc)
 116                        pc->clk_enabled++;
 117        }
 118        return rc;
 119}
 120
 121static void pxa_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
 122{
 123        struct pxa_pwm_chip *pc = to_pxa_pwm_chip(chip);
 124
 125        if (pc->clk_enabled) {
 126                clk_disable_unprepare(pc->clk);
 127                pc->clk_enabled--;
 128        }
 129}
 130
 131static struct pwm_ops pxa_pwm_ops = {
 132        .config = pxa_pwm_config,
 133        .enable = pxa_pwm_enable,
 134        .disable = pxa_pwm_disable,
 135        .owner = THIS_MODULE,
 136};
 137
 138static int pwm_probe(struct platform_device *pdev)
 139{
 140        const struct platform_device_id *id = platform_get_device_id(pdev);
 141        struct pxa_pwm_chip *pwm;
 142        struct resource *r;
 143        int ret = 0;
 144
 145        pwm = devm_kzalloc(&pdev->dev, sizeof(*pwm), GFP_KERNEL);
 146        if (pwm == NULL) {
 147                dev_err(&pdev->dev, "failed to allocate memory\n");
 148                return -ENOMEM;
 149        }
 150
 151        pwm->clk = devm_clk_get(&pdev->dev, NULL);
 152        if (IS_ERR(pwm->clk))
 153                return PTR_ERR(pwm->clk);
 154
 155        pwm->clk_enabled = 0;
 156
 157        pwm->chip.dev = &pdev->dev;
 158        pwm->chip.ops = &pxa_pwm_ops;
 159        pwm->chip.base = -1;
 160        pwm->chip.npwm = (id->driver_data & HAS_SECONDARY_PWM) ? 2 : 1;
 161
 162        r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 163        if (r == NULL) {
 164                dev_err(&pdev->dev, "no memory resource defined\n");
 165                return -ENODEV;
 166        }
 167
 168        pwm->mmio_base = devm_request_and_ioremap(&pdev->dev, r);
 169        if (pwm->mmio_base == NULL)
 170                return -EADDRNOTAVAIL;
 171
 172        ret = pwmchip_add(&pwm->chip);
 173        if (ret < 0) {
 174                dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
 175                return ret;
 176        }
 177
 178        platform_set_drvdata(pdev, pwm);
 179        return 0;
 180}
 181
 182static int pwm_remove(struct platform_device *pdev)
 183{
 184        struct pxa_pwm_chip *chip;
 185
 186        chip = platform_get_drvdata(pdev);
 187        if (chip == NULL)
 188                return -ENODEV;
 189
 190        return pwmchip_remove(&chip->chip);
 191}
 192
 193static struct platform_driver pwm_driver = {
 194        .driver         = {
 195                .name   = "pxa25x-pwm",
 196                .owner  = THIS_MODULE,
 197        },
 198        .probe          = pwm_probe,
 199        .remove         = pwm_remove,
 200        .id_table       = pwm_id_table,
 201};
 202
 203static int __init pwm_init(void)
 204{
 205        return platform_driver_register(&pwm_driver);
 206}
 207arch_initcall(pwm_init);
 208
 209static void __exit pwm_exit(void)
 210{
 211        platform_driver_unregister(&pwm_driver);
 212}
 213module_exit(pwm_exit);
 214
 215MODULE_LICENSE("GPL v2");
 216
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.