linux/drivers/pwm/pwm-vt8500.c
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   1/*
   2 * drivers/pwm/pwm-vt8500.c
   3 *
   4 * Copyright (C) 2012 Tony Prisk <linux@prisktech.co.nz>
   5 * Copyright (C) 2010 Alexey Charkov <alchark@gmail.com>
   6 *
   7 * This software is licensed under the terms of the GNU General Public
   8 * License version 2, as published by the Free Software Foundation, and
   9 * may be copied, distributed, and modified under those terms.
  10 *
  11 * This program is distributed in the hope that it will be useful,
  12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 * GNU General Public License for more details.
  15 */
  16
  17#include <linux/module.h>
  18#include <linux/kernel.h>
  19#include <linux/platform_device.h>
  20#include <linux/slab.h>
  21#include <linux/err.h>
  22#include <linux/io.h>
  23#include <linux/pwm.h>
  24#include <linux/delay.h>
  25#include <linux/clk.h>
  26
  27#include <asm/div64.h>
  28
  29#include <linux/of.h>
  30#include <linux/of_device.h>
  31#include <linux/of_address.h>
  32
  33/*
  34 * SoC architecture allocates register space for 4 PWMs but only
  35 * 2 are currently implemented.
  36 */
  37#define VT8500_NR_PWMS  2
  38
  39struct vt8500_chip {
  40        struct pwm_chip chip;
  41        void __iomem *base;
  42        struct clk *clk;
  43};
  44
  45#define to_vt8500_chip(chip)    container_of(chip, struct vt8500_chip, chip)
  46
  47#define msecs_to_loops(t) (loops_per_jiffy / 1000 * HZ * t)
  48static inline void pwm_busy_wait(void __iomem *reg, u8 bitmask)
  49{
  50        int loops = msecs_to_loops(10);
  51        while ((readb(reg) & bitmask) && --loops)
  52                cpu_relax();
  53
  54        if (unlikely(!loops))
  55                pr_warn("Waiting for status bits 0x%x to clear timed out\n",
  56                           bitmask);
  57}
  58
  59static int vt8500_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
  60                int duty_ns, int period_ns)
  61{
  62        struct vt8500_chip *vt8500 = to_vt8500_chip(chip);
  63        unsigned long long c;
  64        unsigned long period_cycles, prescale, pv, dc;
  65        int err;
  66
  67        err = clk_enable(vt8500->clk);
  68        if (err < 0) {
  69                dev_err(chip->dev, "failed to enable clock\n");
  70                return err;
  71        }
  72
  73        c = clk_get_rate(vt8500->clk);
  74        c = c * period_ns;
  75        do_div(c, 1000000000);
  76        period_cycles = c;
  77
  78        if (period_cycles < 1)
  79                period_cycles = 1;
  80        prescale = (period_cycles - 1) / 4096;
  81        pv = period_cycles / (prescale + 1) - 1;
  82        if (pv > 4095)
  83                pv = 4095;
  84
  85        if (prescale > 1023) {
  86                clk_disable(vt8500->clk);
  87                return -EINVAL;
  88        }
  89
  90        c = (unsigned long long)pv * duty_ns;
  91        do_div(c, period_ns);
  92        dc = c;
  93
  94        pwm_busy_wait(vt8500->base + 0x40 + pwm->hwpwm, (1 << 1));
  95        writel(prescale, vt8500->base + 0x4 + (pwm->hwpwm << 4));
  96
  97        pwm_busy_wait(vt8500->base + 0x40 + pwm->hwpwm, (1 << 2));
  98        writel(pv, vt8500->base + 0x8 + (pwm->hwpwm << 4));
  99
 100        pwm_busy_wait(vt8500->base + 0x40 + pwm->hwpwm, (1 << 3));
 101        writel(dc, vt8500->base + 0xc + (pwm->hwpwm << 4));
 102
 103        clk_disable(vt8500->clk);
 104        return 0;
 105}
 106
 107static int vt8500_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
 108{
 109        int err;
 110        struct vt8500_chip *vt8500 = to_vt8500_chip(chip);
 111
 112        err = clk_enable(vt8500->clk);
 113        if (err < 0) {
 114                dev_err(chip->dev, "failed to enable clock\n");
 115                return err;
 116        }
 117
 118        pwm_busy_wait(vt8500->base + 0x40 + pwm->hwpwm, (1 << 0));
 119        writel(5, vt8500->base + (pwm->hwpwm << 4));
 120        return 0;
 121}
 122
 123static void vt8500_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
 124{
 125        struct vt8500_chip *vt8500 = to_vt8500_chip(chip);
 126
 127        pwm_busy_wait(vt8500->base + 0x40 + pwm->hwpwm, (1 << 0));
 128        writel(0, vt8500->base + (pwm->hwpwm << 4));
 129
 130        clk_disable(vt8500->clk);
 131}
 132
 133static struct pwm_ops vt8500_pwm_ops = {
 134        .enable = vt8500_pwm_enable,
 135        .disable = vt8500_pwm_disable,
 136        .config = vt8500_pwm_config,
 137        .owner = THIS_MODULE,
 138};
 139
 140static const struct of_device_id vt8500_pwm_dt_ids[] = {
 141        { .compatible = "via,vt8500-pwm", },
 142        { /* Sentinel */ }
 143};
 144MODULE_DEVICE_TABLE(of, vt8500_pwm_dt_ids);
 145
 146static int vt8500_pwm_probe(struct platform_device *pdev)
 147{
 148        struct vt8500_chip *chip;
 149        struct resource *r;
 150        struct device_node *np = pdev->dev.of_node;
 151        int ret;
 152
 153        if (!np) {
 154                dev_err(&pdev->dev, "invalid devicetree node\n");
 155                return -EINVAL;
 156        }
 157
 158        chip = devm_kzalloc(&pdev->dev, sizeof(*chip), GFP_KERNEL);
 159        if (chip == NULL) {
 160                dev_err(&pdev->dev, "failed to allocate memory\n");
 161                return -ENOMEM;
 162        }
 163
 164        chip->chip.dev = &pdev->dev;
 165        chip->chip.ops = &vt8500_pwm_ops;
 166        chip->chip.base = -1;
 167        chip->chip.npwm = VT8500_NR_PWMS;
 168
 169        chip->clk = devm_clk_get(&pdev->dev, NULL);
 170        if (IS_ERR(chip->clk)) {
 171                dev_err(&pdev->dev, "clock source not specified\n");
 172                return PTR_ERR(chip->clk);
 173        }
 174
 175        r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 176        if (r == NULL) {
 177                dev_err(&pdev->dev, "no memory resource defined\n");
 178                return -ENODEV;
 179        }
 180
 181        chip->base = devm_request_and_ioremap(&pdev->dev, r);
 182        if (!chip->base)
 183                return -EADDRNOTAVAIL;
 184
 185        ret = clk_prepare(chip->clk);
 186        if (ret < 0) {
 187                dev_err(&pdev->dev, "failed to prepare clock\n");
 188                return ret;
 189        }
 190
 191        ret = pwmchip_add(&chip->chip);
 192        if (ret < 0) {
 193                dev_err(&pdev->dev, "failed to add PWM chip\n");
 194                return ret;
 195        }
 196
 197        platform_set_drvdata(pdev, chip);
 198        return ret;
 199}
 200
 201static int vt8500_pwm_remove(struct platform_device *pdev)
 202{
 203        struct vt8500_chip *chip;
 204
 205        chip = platform_get_drvdata(pdev);
 206        if (chip == NULL)
 207                return -ENODEV;
 208
 209        clk_unprepare(chip->clk);
 210
 211        return pwmchip_remove(&chip->chip);
 212}
 213
 214static struct platform_driver vt8500_pwm_driver = {
 215        .probe          = vt8500_pwm_probe,
 216        .remove         = vt8500_pwm_remove,
 217        .driver         = {
 218                .name   = "vt8500-pwm",
 219                .owner  = THIS_MODULE,
 220                .of_match_table = vt8500_pwm_dt_ids,
 221        },
 222};
 223module_platform_driver(vt8500_pwm_driver);
 224
 225MODULE_DESCRIPTION("VT8500 PWM Driver");
 226MODULE_AUTHOR("Tony Prisk <linux@prisktech.co.nz>");
 227MODULE_LICENSE("GPL v2");
 228
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