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>"); 198