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/platform_device.h>
  18 #include <linux/pwm.h>
  19 #include <linux/slab.h>
  20
  21 #define MX1_PWMC                        0x00   /* PWM Control Register */
  22 #define MX1_PWMS                        0x04   /* PWM Sample Register */
  23 #define MX1_PWMP                        0x08   /* PWM Period Register */
  24
  25 #define MX1_PWMC_EN                     BIT(4)
  26
  27 struct pwm_imx1_chip {
  28         struct clk *clk_ipg;
  29         struct clk *clk_per;
  30         void __iomem *mmio_base;
  31 };
  32
  33 static inline struct pwm_imx1_chip *to_pwm_imx1_chip(struct pwm_chip *chip)
  34 {
  35         return pwmchip_get_drvdata(chip);
  36 }
  37
  38 static int pwm_imx1_clk_prepare_enable(struct pwm_chip *chip)
  39 {
  40         struct pwm_imx1_chip *imx = to_pwm_imx1_chip(chip);
  41         int ret;
  42
  43         ret = clk_prepare_enable(imx->clk_ipg);
  44         if (ret)
  45                 return ret;
  46
  47         ret = clk_prepare_enable(imx->clk_per);
  48         if (ret) {
  49                 clk_disable_unprepare(imx->clk_ipg);
  50                 return ret;
  51         }
  52
  53         return 0;
  54 }
  55
  56 static void pwm_imx1_clk_disable_unprepare(struct pwm_chip *chip)
  57 {
  58         struct pwm_imx1_chip *imx = to_pwm_imx1_chip(chip);
  59
  60         clk_disable_unprepare(imx->clk_per);
  61         clk_disable_unprepare(imx->clk_ipg);
  62 }
  63
  64 static int pwm_imx1_config(struct pwm_chip *chip,
  65                            struct pwm_device *pwm, u64 duty_ns, u64 period_ns)
  66 {
  67         struct pwm_imx1_chip *imx = to_pwm_imx1_chip(chip);
  68         u32 max, p;
  69
  70         /*
  71          * The PWM subsystem allows for exact frequencies. However,
  72          * I cannot connect a scope on my device to the PWM line and
  73          * thus cannot provide the program the PWM controller
  74          * exactly. Instead, I'm relying on the fact that the
  75          * Bootloader (u-boot or WinCE+haret) has programmed the PWM
  76          * function group already. So I'll just modify the PWM sample
  77          * register to follow the ratio of duty_ns vs. period_ns
  78          * accordingly.
  79          *
  80          * This is good enough for programming the brightness of
  81          * the LCD backlight.
  82          *
  83          * The real implementation would divide PERCLK[0] first by
  84          * both the prescaler (/1 .. /128) and then by CLKSEL
  85          * (/2 .. /16).
  86          */
  87         max = readl(imx->mmio_base + MX1_PWMP);
  88         p = mul_u64_u64_div_u64(max, duty_ns, period_ns);
  89
  90         writel(max - p, imx->mmio_base + MX1_PWMS);
  91
  92         return 0;
  93 }
  94
  95 static int pwm_imx1_enable(struct pwm_chip *chip, struct pwm_device *pwm)
  96 {
  97         struct pwm_imx1_chip *imx = to_pwm_imx1_chip(chip);
  98         u32 value;
  99         int ret;
 100
 101         ret = pwm_imx1_clk_prepare_enable(chip);
 102         if (ret < 0)
 103                 return ret;
 104
 105         value = readl(imx->mmio_base + MX1_PWMC);
 106         value |= MX1_PWMC_EN;
 107         writel(value, imx->mmio_base + MX1_PWMC);
 108
 109         return 0;
 110 }
 111
 112 static void pwm_imx1_disable(struct pwm_chip *chip, struct pwm_device *pwm)
 113 {
 114         struct pwm_imx1_chip *imx = to_pwm_imx1_chip(chip);
 115         u32 value;
 116
 117         value = readl(imx->mmio_base + MX1_PWMC);
 118         value &= ~MX1_PWMC_EN;
 119         writel(value, imx->mmio_base + MX1_PWMC);
 120
 121         pwm_imx1_clk_disable_unprepare(chip);
 122 }
 123
 124 static int pwm_imx1_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 125                           const struct pwm_state *state)
 126 {
 127         int err;
 128
 129         if (state->polarity != PWM_POLARITY_NORMAL)
 130                 return -EINVAL;
 131
 132         if (!state->enabled) {
 133                 if (pwm->state.enabled)
 134                         pwm_imx1_disable(chip, pwm);
 135
 136                 return 0;
 137         }
 138
 139         err = pwm_imx1_config(chip, pwm, state->duty_cycle, state->period);
 140         if (err)
 141                 return err;
 142
 143         if (!pwm->state.enabled)
 144                 return pwm_imx1_enable(chip, pwm);
 145
 146         return 0;
 147 }
 148
 149 static const struct pwm_ops pwm_imx1_ops = {
 150         .apply = pwm_imx1_apply,
 151 };
 152
 153 static const struct of_device_id pwm_imx1_dt_ids[] = {
 154         { .compatible = "fsl,imx1-pwm", },
 155         { /* sentinel */ }
 156 };
 157 MODULE_DEVICE_TABLE(of, pwm_imx1_dt_ids);
 158
 159 static int pwm_imx1_probe(struct platform_device *pdev)
 160 {
 161         struct pwm_chip *chip;
 162         struct pwm_imx1_chip *imx;
 163
 164         chip = devm_pwmchip_alloc(&pdev->dev, 1, sizeof(*imx));
 165         if (IS_ERR(chip))
 166                 return PTR_ERR(chip);
 167         imx = to_pwm_imx1_chip(chip);
 168
 169         imx->clk_ipg = devm_clk_get(&pdev->dev, "ipg");
 170         if (IS_ERR(imx->clk_ipg))
 171                 return dev_err_probe(&pdev->dev, PTR_ERR(imx->clk_ipg),
 172                                      "getting ipg clock failed\n");
 173
 174         imx->clk_per = devm_clk_get(&pdev->dev, "per");
 175         if (IS_ERR(imx->clk_per))
 176                 return dev_err_probe(&pdev->dev, PTR_ERR(imx->clk_per),
 177                                      "failed to get peripheral clock\n");
 178
 179         chip->ops = &pwm_imx1_ops;
 180
 181         imx->mmio_base = devm_platform_ioremap_resource(pdev, 0);
 182         if (IS_ERR(imx->mmio_base))
 183                 return PTR_ERR(imx->mmio_base);
 184
 185         return devm_pwmchip_add(&pdev->dev, chip);
 186 }
 187
 188 static struct platform_driver pwm_imx1_driver = {
 189         .driver = {
 190                 .name = "pwm-imx1",
 191                 .of_match_table = pwm_imx1_dt_ids,
 192         },
 193         .probe = pwm_imx1_probe,
 194 };
 195 module_platform_driver(pwm_imx1_driver);
 196
 197 MODULE_LICENSE("GPL v2");
 198 MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>");