1 /* 2 * Copyright (c) 2011 Peter Korsgaard <jacmet@sunsite.dk> 3 * 4 * This file is licensed under the terms of the GNU General Public 5 * License version 2. This program is licensed "as is" without any 6 * warranty of any kind, whether express or implied. 7 */ 8 9 #include <linux/kernel.h> 10 #include <linux/module.h> 11 #include <linux/mod_devicetable.h> 12 #include <linux/slab.h> 13 #include <linux/err.h> 14 #include <linux/clk.h> 15 #include <linux/io.h> 16 #include <linux/hw_random.h> 17 #include <linux/platform_device.h> 18 19 #define TRNG_CR 0x00 20 #define TRNG_ISR 0x1c 21 #define TRNG_ODATA 0x50 22 23 #define TRNG_KEY 0x524e4700 /* RNG */ 24 25 struct atmel_trng { 26 struct clk *clk; 27 void __iomem *base; 28 struct hwrng rng; 29 }; 30 31 static int atmel_trng_read(struct hwrng *rng, void *buf, size_t max, 32 bool wait) 33 { 34 struct atmel_trng *trng = container_of(rng, struct atmel_trng, rng); 35 u32 *data = buf; 36 37 /* data ready? */ 38 if (readl(trng->base + TRNG_ISR) & 1) { 39 *data = readl(trng->base + TRNG_ODATA); 40 /* 41 ensure data ready is only set again AFTER the next data 42 word is ready in case it got set between checking ISR 43 and reading ODATA, so we don't risk re-reading the 44 same word 45 */ 46 readl(trng->base + TRNG_ISR); 47 return 4; 48 } else 49 return 0; 50 } 51 52 static void atmel_trng_enable(struct atmel_trng *trng) 53 { 54 writel(TRNG_KEY | 1, trng->base + TRNG_CR); 55 } 56 57 static void atmel_trng_disable(struct atmel_trng *trng) 58 { 59 writel(TRNG_KEY, trng->base + TRNG_CR); 60 } 61 62 static int atmel_trng_probe(struct platform_device *pdev) 63 { 64 struct atmel_trng *trng; 65 struct resource *res; 66 int ret; 67 68 trng = devm_kzalloc(&pdev->dev, sizeof(*trng), GFP_KERNEL); 69 if (!trng) 70 return -ENOMEM; 71 72 res = platform_get_resource(pdev, IORESOURCE_MEM, 0); 73 trng->base = devm_ioremap_resource(&pdev->dev, res); 74 if (IS_ERR(trng->base)) 75 return PTR_ERR(trng->base); 76 77 trng->clk = devm_clk_get(&pdev->dev, NULL); 78 if (IS_ERR(trng->clk)) 79 return PTR_ERR(trng->clk); 80 81 ret = clk_prepare_enable(trng->clk); 82 if (ret) 83 return ret; 84 85 atmel_trng_enable(trng); 86 trng->rng.name = pdev->name; 87 trng->rng.read = atmel_trng_read; 88 89 ret = hwrng_register(&trng->rng); 90 if (ret) 91 goto err_register; 92 93 platform_set_drvdata(pdev, trng); 94 95 return 0; 96 97 err_register: 98 clk_disable_unprepare(trng->clk); 99 return ret; 100 } 101 102 static int atmel_trng_remove(struct platform_device *pdev) 103 { 104 struct atmel_trng *trng = platform_get_drvdata(pdev); 105 106 hwrng_unregister(&trng->rng); 107 108 atmel_trng_disable(trng); 109 clk_disable_unprepare(trng->clk); 110 111 return 0; 112 } 113 114 #ifdef CONFIG_PM 115 static int atmel_trng_suspend(struct device *dev) 116 { 117 struct atmel_trng *trng = dev_get_drvdata(dev); 118 119 atmel_trng_disable(trng); 120 clk_disable_unprepare(trng->clk); 121 122 return 0; 123 } 124 125 static int atmel_trng_resume(struct device *dev) 126 { 127 struct atmel_trng *trng = dev_get_drvdata(dev); 128 int ret; 129 130 ret = clk_prepare_enable(trng->clk); 131 if (ret) 132 return ret; 133 134 atmel_trng_enable(trng); 135 136 return 0; 137 } 138 139 static const struct dev_pm_ops atmel_trng_pm_ops = { 140 .suspend = atmel_trng_suspend, 141 .resume = atmel_trng_resume, 142 }; 143 #endif /* CONFIG_PM */ 144 145 static const struct of_device_id atmel_trng_dt_ids[] = { 146 { .compatible = "atmel,at91sam9g45-trng" }, 147 { /* sentinel */ } 148 }; 149 MODULE_DEVICE_TABLE(of, atmel_trng_dt_ids); 150 151 static struct platform_driver atmel_trng_driver = { 152 .probe = atmel_trng_probe, 153 .remove = atmel_trng_remove, 154 .driver = { 155 .name = "atmel-trng", 156 #ifdef CONFIG_PM 157 .pm = &atmel_trng_pm_ops, 158 #endif /* CONFIG_PM */ 159 .of_match_table = atmel_trng_dt_ids, 160 }, 161 }; 162 163 module_platform_driver(atmel_trng_driver); 164 165 MODULE_LICENSE("GPL"); 166 MODULE_AUTHOR("Peter Korsgaard <jacmet@sunsite.dk>"); 167 MODULE_DESCRIPTION("Atmel true random number generator driver"); 168