drivers/pwm/pwm-imx.c

   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
  42 struct 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
  53 static 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
 124 static 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
 137 static 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
 149 static 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
 156 static 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
 198 static 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
 209 static 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
 217 static int __init imx_pwm_init(void)
 218 {
 219         return platform_driver_register(&imx_pwm_driver);
 220 }
 221 arch_initcall(imx_pwm_init);
 222
 223 static void __exit imx_pwm_exit(void)
 224 {
 225         platform_driver_unregister(&imx_pwm_driver);
 226 }
 227 module_exit(imx_pwm_exit);
 228
 229 MODULE_LICENSE("GPL v2");
 230 MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>");