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>"); 199