pwm-imx1.c (4833B)
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, u64 duty_ns, u64 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 = mul_u64_u64_div_u64(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 int pwm_imx1_apply(struct pwm_chip *chip, struct pwm_device *pwm, 124 const struct pwm_state *state) 125{ 126 int err; 127 128 if (state->polarity != PWM_POLARITY_NORMAL) 129 return -EINVAL; 130 131 if (!state->enabled) { 132 if (pwm->state.enabled) 133 pwm_imx1_disable(chip, pwm); 134 135 return 0; 136 } 137 138 err = pwm_imx1_config(chip, pwm, state->duty_cycle, state->period); 139 if (err) 140 return err; 141 142 if (!pwm->state.enabled) 143 return pwm_imx1_enable(chip, pwm); 144 145 return 0; 146} 147 148static const struct pwm_ops pwm_imx1_ops = { 149 .apply = pwm_imx1_apply, 150 .owner = THIS_MODULE, 151}; 152 153static const struct of_device_id pwm_imx1_dt_ids[] = { 154 { .compatible = "fsl,imx1-pwm", }, 155 { /* sentinel */ } 156}; 157MODULE_DEVICE_TABLE(of, pwm_imx1_dt_ids); 158 159static int pwm_imx1_probe(struct platform_device *pdev) 160{ 161 struct pwm_imx1_chip *imx; 162 163 imx = devm_kzalloc(&pdev->dev, sizeof(*imx), GFP_KERNEL); 164 if (!imx) 165 return -ENOMEM; 166 167 imx->clk_ipg = devm_clk_get(&pdev->dev, "ipg"); 168 if (IS_ERR(imx->clk_ipg)) 169 return dev_err_probe(&pdev->dev, PTR_ERR(imx->clk_ipg), 170 "getting ipg clock failed\n"); 171 172 imx->clk_per = devm_clk_get(&pdev->dev, "per"); 173 if (IS_ERR(imx->clk_per)) 174 return dev_err_probe(&pdev->dev, PTR_ERR(imx->clk_per), 175 "failed to get peripheral clock\n"); 176 177 imx->chip.ops = &pwm_imx1_ops; 178 imx->chip.dev = &pdev->dev; 179 imx->chip.npwm = 1; 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, &imx->chip); 186} 187 188static 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}; 195module_platform_driver(pwm_imx1_driver); 196 197MODULE_LICENSE("GPL v2"); 198MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>");