drivers/pwm/pwm-imx1.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * simple driver for PWM (Pulse Width Modulator) controller
   4  *
   5  * Derived from pxa PWM driver by eric miao <eric.miao@marvell.com>
   6  */
   7
   8 #include <linux/bitfield.h>
   9 #include <linux/bitops.h>
  10 #include <linux/clk.h>
  11 #include <linux/delay.h>
  12 #include <linux/err.h>
  13 #include <linux/io.h>
  14 #include <linux/kernel.h>
  15 #include <linux/module.h>
  16 #include <linux/of.h>
  17 #include <linux/of_device.h>
  18 #include <linux/platform_device.h>
  19 #include <linux/pwm.h>
  20 #include <linux/slab.h>
  21
  22 #define MX1_PWMC                        0x00   /* PWM Control Register */
  23 #define MX1_PWMS                        0x04   /* PWM Sample Register */
  24 #define MX1_PWMP                        0x08   /* PWM Period Register */
  25
  26 #define MX1_PWMC_EN                     BIT(4)
  27
  28 struct pwm_imx1_chip {
  29         struct clk *clk_ipg;
  30         struct clk *clk_per;
  31         void __iomem *mmio_base;
  32         struct pwm_chip chip;
  33 };
  34
  35 #define to_pwm_imx1_chip(chip)  container_of(chip, struct pwm_imx1_chip, chip)
  36
  37 static int pwm_imx1_clk_prepare_enable(struct pwm_chip *chip)
  38 {
  39         struct pwm_imx1_chip *imx = to_pwm_imx1_chip(chip);
  40         int ret;
  41
  42         ret = clk_prepare_enable(imx->clk_ipg);
  43         if (ret)
  44                 return ret;
  45
  46         ret = clk_prepare_enable(imx->clk_per);
  47         if (ret) {
  48                 clk_disable_unprepare(imx->clk_ipg);
  49                 return ret;
  50         }
  51
  52         return 0;
  53 }
  54
  55 static void pwm_imx1_clk_disable_unprepare(struct pwm_chip *chip)
  56 {
  57         struct pwm_imx1_chip *imx = to_pwm_imx1_chip(chip);
  58
  59         clk_disable_unprepare(imx->clk_per);
  60         clk_disable_unprepare(imx->clk_ipg);
  61 }
  62
  63 static int pwm_imx1_config(struct pwm_chip *chip,
  64                            struct pwm_device *pwm, int duty_ns, int period_ns)
  65 {
  66         struct pwm_imx1_chip *imx = to_pwm_imx1_chip(chip);
  67         u32 max, p;
  68
  69         /*
  70          * The PWM subsystem allows for exact frequencies. However,
  71          * I cannot connect a scope on my device to the PWM line and
  72          * thus cannot provide the program the PWM controller
  73          * exactly. Instead, I'm relying on the fact that the
  74          * Bootloader (u-boot or WinCE+haret) has programmed the PWM
  75          * function group already. So I'll just modify the PWM sample
  76          * register to follow the ratio of duty_ns vs. period_ns
  77          * accordingly.
  78          *
  79          * This is good enough for programming the brightness of
  80          * the LCD backlight.
  81          *
  82          * The real implementation would divide PERCLK[0] first by
  83          * both the prescaler (/1 .. /128) and then by CLKSEL
  84          * (/2 .. /16).
  85          */
  86         max = readl(imx->mmio_base + MX1_PWMP);
  87         p = max * duty_ns / period_ns;
  88
  89         writel(max - p, imx->mmio_base + MX1_PWMS);
  90
  91         return 0;
  92 }
  93
  94 static int pwm_imx1_enable(struct pwm_chip *chip, struct pwm_device *pwm)
  95 {
  96         struct pwm_imx1_chip *imx = to_pwm_imx1_chip(chip);
  97         u32 value;
  98         int ret;
  99
 100         ret = pwm_imx1_clk_prepare_enable(chip);
 101         if (ret < 0)
 102                 return ret;
 103
 104         value = readl(imx->mmio_base + MX1_PWMC);
 105         value |= MX1_PWMC_EN;
 106         writel(value, imx->mmio_base + MX1_PWMC);
 107
 108         return 0;
 109 }
 110
 111 static void pwm_imx1_disable(struct pwm_chip *chip, struct pwm_device *pwm)
 112 {
 113         struct pwm_imx1_chip *imx = to_pwm_imx1_chip(chip);
 114         u32 value;
 115
 116         value = readl(imx->mmio_base + MX1_PWMC);
 117         value &= ~MX1_PWMC_EN;
 118         writel(value, imx->mmio_base + MX1_PWMC);
 119
 120         pwm_imx1_clk_disable_unprepare(chip);
 121 }
 122
 123 static const struct pwm_ops pwm_imx1_ops = {
 124         .enable = pwm_imx1_enable,
 125         .disable = pwm_imx1_disable,
 126         .config = pwm_imx1_config,
 127         .owner = THIS_MODULE,
 128 };
 129
 130 static const struct of_device_id pwm_imx1_dt_ids[] = {
 131         { .compatible = "fsl,imx1-pwm", },
 132         { /* sentinel */ }
 133 };
 134 MODULE_DEVICE_TABLE(of, pwm_imx1_dt_ids);
 135
 136 static int pwm_imx1_probe(struct platform_device *pdev)
 137 {
 138         struct pwm_imx1_chip *imx;
 139
 140         imx = devm_kzalloc(&pdev->dev, sizeof(*imx), GFP_KERNEL);
 141         if (!imx)
 142                 return -ENOMEM;
 143
 144         imx->clk_ipg = devm_clk_get(&pdev->dev, "ipg");
 145         if (IS_ERR(imx->clk_ipg))
 146                 return dev_err_probe(&pdev->dev, PTR_ERR(imx->clk_ipg),
 147                                      "getting ipg clock failed\n");
 148
 149         imx->clk_per = devm_clk_get(&pdev->dev, "per");
 150         if (IS_ERR(imx->clk_per))
 151                 return dev_err_probe(&pdev->dev, PTR_ERR(imx->clk_per),
 152                                      "failed to get peripheral clock\n");
 153
 154         imx->chip.ops = &pwm_imx1_ops;
 155         imx->chip.dev = &pdev->dev;
 156         imx->chip.npwm = 1;
 157
 158         imx->mmio_base = devm_platform_ioremap_resource(pdev, 0);
 159         if (IS_ERR(imx->mmio_base))
 160                 return PTR_ERR(imx->mmio_base);
 161
 162         return devm_pwmchip_add(&pdev->dev, &imx->chip);
 163 }
 164
 165 static struct platform_driver pwm_imx1_driver = {
 166         .driver = {
 167                 .name = "pwm-imx1",
 168                 .of_match_table = pwm_imx1_dt_ids,
 169         },
 170         .probe = pwm_imx1_probe,
 171 };
 172 module_platform_driver(pwm_imx1_driver);
 173
 174 MODULE_LICENSE("GPL v2");
 175 MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>");