LXR linux/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
  28struct 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
  37static 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
  55static 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
  63static 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
  94static 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
 111static 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
 123static 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
 130static const struct of_device_id pwm_imx1_dt_ids[] = {
 131        { .compatible = "fsl,imx1-pwm", },
 132        { /* sentinel */ }
 133};
 134MODULE_DEVICE_TABLE(of, pwm_imx1_dt_ids);
 135
 136static 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
 165static 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};
 172module_platform_driver(pwm_imx1_driver);
 173
 174MODULE_LICENSE("GPL v2");
 175MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>");
 176