1 /* 2 * Copyright (c) 2015, Daniel Thompson 3 * 4 * This file is free software; you can redistribute it and/or 5 * modify it under the terms of the GNU General Public License 6 * as published by the Free Software Foundation; either version 2 7 * of the License, or (at your option) any later version. 8 * 9 * This file is distributed in the hope that it will be useful, 10 * but WITHOUT ANY WARRANTY; without even the implied warranty of 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 12 * GNU General Public License for more details. 13 */ 14 15 #include <linux/clk.h> 16 #include <linux/delay.h> 17 #include <linux/hw_random.h> 18 #include <linux/io.h> 19 #include <linux/iopoll.h> 20 #include <linux/kernel.h> 21 #include <linux/module.h> 22 #include <linux/of_address.h> 23 #include <linux/of_platform.h> 24 #include <linux/pm_runtime.h> 25 #include <linux/reset.h> 26 #include <linux/slab.h> 27 28 #define RNG_CR 0x00 29 #define RNG_CR_RNGEN BIT(2) 30 #define RNG_CR_CED BIT(5) 31 32 #define RNG_SR 0x04 33 #define RNG_SR_SEIS BIT(6) 34 #define RNG_SR_CEIS BIT(5) 35 #define RNG_SR_DRDY BIT(0) 36 37 #define RNG_DR 0x08 38 39 struct stm32_rng_private { 40 struct hwrng rng; 41 void __iomem *base; 42 struct clk *clk; 43 struct reset_control *rst; 44 bool ced; 45 }; 46 47 static int stm32_rng_read(struct hwrng *rng, void *data, size_t max, bool wait) 48 { 49 struct stm32_rng_private *priv = 50 container_of(rng, struct stm32_rng_private, rng); 51 u32 sr; 52 int retval = 0; 53 54 pm_runtime_get_sync((struct device *) priv->rng.priv); 55 56 while (max > sizeof(u32)) { 57 sr = readl_relaxed(priv->base + RNG_SR); 58 /* Manage timeout which is based on timer and take */ 59 /* care of initial delay time when enabling rng */ 60 if (!sr && wait) { 61 retval = readl_relaxed_poll_timeout_atomic(priv->base 62 + RNG_SR, 63 sr, sr, 64 10, 50000); 65 if (retval) 66 dev_err((struct device *)priv->rng.priv, 67 "%s: timeout %x!\n", __func__, sr); 68 } 69 70 /* If error detected or data not ready... */ 71 if (sr != RNG_SR_DRDY) { 72 if (WARN_ONCE(sr & (RNG_SR_SEIS | RNG_SR_CEIS), 73 "bad RNG status - %x\n", sr)) 74 writel_relaxed(0, priv->base + RNG_SR); 75 break; 76 } 77 78 *(u32 *)data = readl_relaxed(priv->base + RNG_DR); 79 80 retval += sizeof(u32); 81 data += sizeof(u32); 82 max -= sizeof(u32); 83 } 84 85 pm_runtime_mark_last_busy((struct device *) priv->rng.priv); 86 pm_runtime_put_sync_autosuspend((struct device *) priv->rng.priv); 87 88 return retval || !wait ? retval : -EIO; 89 } 90 91 static int stm32_rng_init(struct hwrng *rng) 92 { 93 struct stm32_rng_private *priv = 94 container_of(rng, struct stm32_rng_private, rng); 95 int err; 96 97 err = clk_prepare_enable(priv->clk); 98 if (err) 99 return err; 100 101 if (priv->ced) 102 writel_relaxed(RNG_CR_RNGEN, priv->base + RNG_CR); 103 else 104 writel_relaxed(RNG_CR_RNGEN | RNG_CR_CED, 105 priv->base + RNG_CR); 106 107 /* clear error indicators */ 108 writel_relaxed(0, priv->base + RNG_SR); 109 110 return 0; 111 } 112 113 static void stm32_rng_cleanup(struct hwrng *rng) 114 { 115 struct stm32_rng_private *priv = 116 container_of(rng, struct stm32_rng_private, rng); 117 118 writel_relaxed(0, priv->base + RNG_CR); 119 clk_disable_unprepare(priv->clk); 120 } 121 122 static int stm32_rng_probe(struct platform_device *ofdev) 123 { 124 struct device *dev = &ofdev->dev; 125 struct device_node *np = ofdev->dev.of_node; 126 struct stm32_rng_private *priv; 127 struct resource res; 128 int err; 129 130 priv = devm_kzalloc(dev, sizeof(struct stm32_rng_private), GFP_KERNEL); 131 if (!priv) 132 return -ENOMEM; 133 134 err = of_address_to_resource(np, 0, &res); 135 if (err) 136 return err; 137 138 priv->base = devm_ioremap_resource(dev, &res); 139 if (IS_ERR(priv->base)) 140 return PTR_ERR(priv->base); 141 142 priv->clk = devm_clk_get(&ofdev->dev, NULL); 143 if (IS_ERR(priv->clk)) 144 return PTR_ERR(priv->clk); 145 146 priv->rst = devm_reset_control_get(&ofdev->dev, NULL); 147 if (!IS_ERR(priv->rst)) { 148 reset_control_assert(priv->rst); 149 udelay(2); 150 reset_control_deassert(priv->rst); 151 } 152 153 priv->ced = of_property_read_bool(np, "clock-error-detect"); 154 155 dev_set_drvdata(dev, priv); 156 157 priv->rng.name = dev_driver_string(dev), 158 #ifndef CONFIG_PM 159 priv->rng.init = stm32_rng_init, 160 priv->rng.cleanup = stm32_rng_cleanup, 161 #endif 162 priv->rng.read = stm32_rng_read, 163 priv->rng.priv = (unsigned long) dev; 164 165 pm_runtime_set_autosuspend_delay(dev, 100); 166 pm_runtime_use_autosuspend(dev); 167 pm_runtime_enable(dev); 168 169 return devm_hwrng_register(dev, &priv->rng); 170 } 171 172 #ifdef CONFIG_PM 173 static int stm32_rng_runtime_suspend(struct device *dev) 174 { 175 struct stm32_rng_private *priv = dev_get_drvdata(dev); 176 177 stm32_rng_cleanup(&priv->rng); 178 179 return 0; 180 } 181 182 static int stm32_rng_runtime_resume(struct device *dev) 183 { 184 struct stm32_rng_private *priv = dev_get_drvdata(dev); 185 186 return stm32_rng_init(&priv->rng); 187 } 188 #endif 189 190 static UNIVERSAL_DEV_PM_OPS(stm32_rng_pm_ops, stm32_rng_runtime_suspend, 191 stm32_rng_runtime_resume, NULL); 192 193 static const struct of_device_id stm32_rng_match[] = { 194 { 195 .compatible = "st,stm32-rng", 196 }, 197 {}, 198 }; 199 MODULE_DEVICE_TABLE(of, stm32_rng_match); 200 201 static struct platform_driver stm32_rng_driver = { 202 .driver = { 203 .name = "stm32-rng", 204 .pm = &stm32_rng_pm_ops, 205 .of_match_table = stm32_rng_match, 206 }, 207 .probe = stm32_rng_probe, 208 }; 209 210 module_platform_driver(stm32_rng_driver); 211 212 MODULE_LICENSE("GPL"); 213 MODULE_AUTHOR("Daniel Thompson <daniel.thompson@linaro.org>"); 214 MODULE_DESCRIPTION("STMicroelectronics STM32 RNG device driver"); 215