drivers/pwm/pwm-vt8500.c

   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
  39 struct 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)
  48 static 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
  59 static 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
 107 static 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
 123 static 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
 133 static 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
 140 static const struct of_device_id vt8500_pwm_dt_ids[] = {
 141         { .compatible = "via,vt8500-pwm", },
 142         { /* Sentinel */ }
 143 };
 144 MODULE_DEVICE_TABLE(of, vt8500_pwm_dt_ids);
 145
 146 static 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
 201 static 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
 214 static 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 };
 223 module_platform_driver(vt8500_pwm_driver);
 224
 225 MODULE_DESCRIPTION("VT8500 PWM Driver");
 226 MODULE_AUTHOR("Tony Prisk <linux@prisktech.co.nz>");
 227 MODULE_LICENSE("GPL v2");