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/slab.h> 12 #include <linux/err.h> 13 #include <linux/clk.h> 14 #include <linux/io.h> 15 #include <linux/hw_random.h> 16 #include <linux/platform_device.h> 17 18 #define TRNG_CR 0x00 19 #define TRNG_ISR 0x1c 20 #define TRNG_ODATA 0x50 21 22 #define TRNG_KEY 0x524e4700 /* RNG */ 23 24 struct atmel_trng { 25 struct clk *clk; 26 void __iomem *base; 27 struct hwrng rng; 28 }; 29 30 static int atmel_trng_read(struct hwrng *rng, void *buf, size_t max, 31 bool wait) 32 { 33 struct atmel_trng *trng = container_of(rng, struct atmel_trng, rng); 34 u32 *data = buf; 35 36 /* data ready? */ 37 if (readl(trng->base + TRNG_ISR) & 1) { 38 *data = readl(trng->base + TRNG_ODATA); 39 /* 40 ensure data ready is only set again AFTER the next data 41 word is ready in case it got set between checking ISR 42 and reading ODATA, so we don't risk re-reading the 43 same word 44 */ 45 readl(trng->base + TRNG_ISR); 46 return 4; 47 } else 48 return 0; 49 } 50 51 static int atmel_trng_probe(struct platform_device *pdev) 52 { 53 struct atmel_trng *trng; 54 struct resource *res; 55 int ret; 56 57 trng = devm_kzalloc(&pdev->dev, sizeof(*trng), GFP_KERNEL); 58 if (!trng) 59 return -ENOMEM; 60 61 res = platform_get_resource(pdev, IORESOURCE_MEM, 0); 62 trng->base = devm_ioremap_resource(&pdev->dev, res); 63 if (IS_ERR(trng->base)) 64 return PTR_ERR(trng->base); 65 66 trng->clk = devm_clk_get(&pdev->dev, NULL); 67 if (IS_ERR(trng->clk)) 68 return PTR_ERR(trng->clk); 69 70 ret = clk_prepare_enable(trng->clk); 71 if (ret) 72 return ret; 73 74 writel(TRNG_KEY | 1, trng->base + TRNG_CR); 75 trng->rng.name = pdev->name; 76 trng->rng.read = atmel_trng_read; 77 78 ret = hwrng_register(&trng->rng); 79 if (ret) 80 goto err_register; 81 82 platform_set_drvdata(pdev, trng); 83 84 return 0; 85 86 err_register: 87 clk_disable(trng->clk); 88 return ret; 89 } 90 91 static int atmel_trng_remove(struct platform_device *pdev) 92 { 93 struct atmel_trng *trng = platform_get_drvdata(pdev); 94 95 hwrng_unregister(&trng->rng); 96 97 writel(TRNG_KEY, trng->base + TRNG_CR); 98 clk_disable_unprepare(trng->clk); 99 100 return 0; 101 } 102 103 #ifdef CONFIG_PM 104 static int atmel_trng_suspend(struct device *dev) 105 { 106 struct atmel_trng *trng = dev_get_drvdata(dev); 107 108 clk_disable_unprepare(trng->clk); 109 110 return 0; 111 } 112 113 static int atmel_trng_resume(struct device *dev) 114 { 115 struct atmel_trng *trng = dev_get_drvdata(dev); 116 117 return clk_prepare_enable(trng->clk); 118 } 119 120 static const struct dev_pm_ops atmel_trng_pm_ops = { 121 .suspend = atmel_trng_suspend, 122 .resume = atmel_trng_resume, 123 }; 124 #endif /* CONFIG_PM */ 125 126 static const struct of_device_id atmel_trng_dt_ids[] = { 127 { .compatible = "atmel,at91sam9g45-trng" }, 128 { /* sentinel */ } 129 }; 130 MODULE_DEVICE_TABLE(of, atmel_trng_dt_ids); 131 132 static struct platform_driver atmel_trng_driver = { 133 .probe = atmel_trng_probe, 134 .remove = atmel_trng_remove, 135 .driver = { 136 .name = "atmel-trng", 137 #ifdef CONFIG_PM 138 .pm = &atmel_trng_pm_ops, 139 #endif /* CONFIG_PM */ 140 .of_match_table = atmel_trng_dt_ids, 141 }, 142 }; 143 144 module_platform_driver(atmel_trng_driver); 145 146 MODULE_LICENSE("GPL"); 147 MODULE_AUTHOR("Peter Korsgaard <jacmet@sunsite.dk>"); 148 MODULE_DESCRIPTION("Atmel true random number generator driver"); 149