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