linux/drivers/pwm/pwm-imx.c
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   1/*
   2 * simple driver for PWM (Pulse Width Modulator) controller
   3 *
   4 * This program is free software; you can redistribute it and/or modify
   5 * it under the terms of the GNU General Public License version 2 as
   6 * published by the Free Software Foundation.
   7 *
   8 * Derived from pxa PWM driver by eric miao <eric.miao@marvell.com>
   9 */
  10
  11#include <linux/module.h>
  12#include <linux/kernel.h>
  13#include <linux/platform_device.h>
  14#include <linux/slab.h>
  15#include <linux/err.h>
  16#include <linux/clk.h>
  17#include <linux/io.h>
  18#include <linux/pwm.h>
  19#include <mach/hardware.h>
  20
  21
  22/* i.MX1 and i.MX21 share the same PWM function block: */
  23
  24#define MX1_PWMC    0x00   /* PWM Control Register */
  25#define MX1_PWMS    0x04   /* PWM Sample Register */
  26#define MX1_PWMP    0x08   /* PWM Period Register */
  27
  28
  29/* i.MX27, i.MX31, i.MX35 share the same PWM function block: */
  30
  31#define MX3_PWMCR                 0x00    /* PWM Control Register */
  32#define MX3_PWMSAR                0x0C    /* PWM Sample Register */
  33#define MX3_PWMPR                 0x10    /* PWM Period Register */
  34#define MX3_PWMCR_PRESCALER(x)    (((x - 1) & 0xFFF) << 4)
  35#define MX3_PWMCR_DOZEEN                (1 << 24)
  36#define MX3_PWMCR_WAITEN                (1 << 23)
  37#define MX3_PWMCR_DBGEN                 (1 << 22)
  38#define MX3_PWMCR_CLKSRC_IPG_HIGH (2 << 16)
  39#define MX3_PWMCR_CLKSRC_IPG      (1 << 16)
  40#define MX3_PWMCR_EN              (1 << 0)
  41
  42struct imx_chip {
  43        struct clk      *clk;
  44
  45        int             clk_enabled;
  46        void __iomem    *mmio_base;
  47
  48        struct pwm_chip chip;
  49};
  50
  51#define to_imx_chip(chip)       container_of(chip, struct imx_chip, chip)
  52
  53static int imx_pwm_config(struct pwm_chip *chip,
  54                struct pwm_device *pwm, int duty_ns, int period_ns)
  55{
  56        struct imx_chip *imx = to_imx_chip(chip);
  57
  58        if (!(cpu_is_mx1() || cpu_is_mx21())) {
  59                unsigned long long c;
  60                unsigned long period_cycles, duty_cycles, prescale;
  61                u32 cr;
  62
  63                c = clk_get_rate(imx->clk);
  64                c = c * period_ns;
  65                do_div(c, 1000000000);
  66                period_cycles = c;
  67
  68                prescale = period_cycles / 0x10000 + 1;
  69
  70                period_cycles /= prescale;
  71                c = (unsigned long long)period_cycles * duty_ns;
  72                do_div(c, period_ns);
  73                duty_cycles = c;
  74
  75                /*
  76                 * according to imx pwm RM, the real period value should be
  77                 * PERIOD value in PWMPR plus 2.
  78                 */
  79                if (period_cycles > 2)
  80                        period_cycles -= 2;
  81                else
  82                        period_cycles = 0;
  83
  84                writel(duty_cycles, imx->mmio_base + MX3_PWMSAR);
  85                writel(period_cycles, imx->mmio_base + MX3_PWMPR);
  86
  87                cr = MX3_PWMCR_PRESCALER(prescale) |
  88                        MX3_PWMCR_DOZEEN | MX3_PWMCR_WAITEN |
  89                        MX3_PWMCR_DBGEN | MX3_PWMCR_EN;
  90
  91                if (cpu_is_mx25())
  92                        cr |= MX3_PWMCR_CLKSRC_IPG;
  93                else
  94                        cr |= MX3_PWMCR_CLKSRC_IPG_HIGH;
  95
  96                writel(cr, imx->mmio_base + MX3_PWMCR);
  97        } else if (cpu_is_mx1() || cpu_is_mx21()) {
  98                /* The PWM subsystem allows for exact frequencies. However,
  99                 * I cannot connect a scope on my device to the PWM line and
 100                 * thus cannot provide the program the PWM controller
 101                 * exactly. Instead, I'm relying on the fact that the
 102                 * Bootloader (u-boot or WinCE+haret) has programmed the PWM
 103                 * function group already. So I'll just modify the PWM sample
 104                 * register to follow the ratio of duty_ns vs. period_ns
 105                 * accordingly.
 106                 *
 107                 * This is good enough for programming the brightness of
 108                 * the LCD backlight.
 109                 *
 110                 * The real implementation would divide PERCLK[0] first by
 111                 * both the prescaler (/1 .. /128) and then by CLKSEL
 112                 * (/2 .. /16).
 113                 */
 114                u32 max = readl(imx->mmio_base + MX1_PWMP);
 115                u32 p = max * duty_ns / period_ns;
 116                writel(max - p, imx->mmio_base + MX1_PWMS);
 117        } else {
 118                BUG();
 119        }
 120
 121        return 0;
 122}
 123
 124static int imx_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
 125{
 126        struct imx_chip *imx = to_imx_chip(chip);
 127        int rc = 0;
 128
 129        if (!imx->clk_enabled) {
 130                rc = clk_prepare_enable(imx->clk);
 131                if (!rc)
 132                        imx->clk_enabled = 1;
 133        }
 134        return rc;
 135}
 136
 137static void imx_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
 138{
 139        struct imx_chip *imx = to_imx_chip(chip);
 140
 141        writel(0, imx->mmio_base + MX3_PWMCR);
 142
 143        if (imx->clk_enabled) {
 144                clk_disable_unprepare(imx->clk);
 145                imx->clk_enabled = 0;
 146        }
 147}
 148
 149static struct pwm_ops imx_pwm_ops = {
 150        .enable = imx_pwm_enable,
 151        .disable = imx_pwm_disable,
 152        .config = imx_pwm_config,
 153        .owner = THIS_MODULE,
 154};
 155
 156static int __devinit imx_pwm_probe(struct platform_device *pdev)
 157{
 158        struct imx_chip *imx;
 159        struct resource *r;
 160        int ret = 0;
 161
 162        imx = devm_kzalloc(&pdev->dev, sizeof(*imx), GFP_KERNEL);
 163        if (imx == NULL) {
 164                dev_err(&pdev->dev, "failed to allocate memory\n");
 165                return -ENOMEM;
 166        }
 167
 168        imx->clk = devm_clk_get(&pdev->dev, "pwm");
 169
 170        if (IS_ERR(imx->clk))
 171                return PTR_ERR(imx->clk);
 172
 173        imx->chip.ops = &imx_pwm_ops;
 174        imx->chip.dev = &pdev->dev;
 175        imx->chip.base = -1;
 176        imx->chip.npwm = 1;
 177
 178        imx->clk_enabled = 0;
 179
 180        r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 181        if (r == NULL) {
 182                dev_err(&pdev->dev, "no memory resource defined\n");
 183                return -ENODEV;
 184        }
 185
 186        imx->mmio_base = devm_request_and_ioremap(&pdev->dev, r);
 187        if (imx->mmio_base == NULL)
 188                return -EADDRNOTAVAIL;
 189
 190        ret = pwmchip_add(&imx->chip);
 191        if (ret < 0)
 192                return ret;
 193
 194        platform_set_drvdata(pdev, imx);
 195        return 0;
 196}
 197
 198static int __devexit imx_pwm_remove(struct platform_device *pdev)
 199{
 200        struct imx_chip *imx;
 201
 202        imx = platform_get_drvdata(pdev);
 203        if (imx == NULL)
 204                return -ENODEV;
 205
 206        return pwmchip_remove(&imx->chip);
 207}
 208
 209static struct platform_driver imx_pwm_driver = {
 210        .driver         = {
 211                .name   = "mxc_pwm",
 212        },
 213        .probe          = imx_pwm_probe,
 214        .remove         = __devexit_p(imx_pwm_remove),
 215};
 216
 217static int __init imx_pwm_init(void)
 218{
 219        return platform_driver_register(&imx_pwm_driver);
 220}
 221arch_initcall(imx_pwm_init);
 222
 223static void __exit imx_pwm_exit(void)
 224{
 225        platform_driver_unregister(&imx_pwm_driver);
 226}
 227module_exit(imx_pwm_exit);
 228
 229MODULE_LICENSE("GPL v2");
 230MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>");
 231
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