drivers/char/hw_random/atmel-rng.c

   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_ODATA) & 1) {
  38                 *data = readl(trng->base + TRNG_ODATA);
  39                 return 4;
  40         } else
  41                 return 0;
  42 }
  43
  44 static int atmel_trng_probe(struct platform_device *pdev)
  45 {
  46         struct atmel_trng *trng;
  47         struct resource *res;
  48         int ret;
  49
  50         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  51         if (!res)
  52                 return -EINVAL;
  53
  54         trng = devm_kzalloc(&pdev->dev, sizeof(*trng), GFP_KERNEL);
  55         if (!trng)
  56                 return -ENOMEM;
  57
  58         if (!devm_request_mem_region(&pdev->dev, res->start,
  59                                      resource_size(res), pdev->name))
  60                 return -EBUSY;
  61
  62         trng->base = devm_ioremap(&pdev->dev, res->start, resource_size(res));
  63         if (!trng->base)
  64                 return -EBUSY;
  65
  66         trng->clk = clk_get(&pdev->dev, NULL);
  67         if (IS_ERR(trng->clk))
  68                 return PTR_ERR(trng->clk);
  69
  70         ret = clk_enable(trng->clk);
  71         if (ret)
  72                 goto err_enable;
  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 err_enable:
  89         clk_put(trng->clk);
  90
  91         return ret;
  92 }
  93
  94 static int __devexit atmel_trng_remove(struct platform_device *pdev)
  95 {
  96         struct atmel_trng *trng = platform_get_drvdata(pdev);
  97
  98         hwrng_unregister(&trng->rng);
  99
 100         writel(TRNG_KEY, trng->base + TRNG_CR);
 101         clk_disable(trng->clk);
 102         clk_put(trng->clk);
 103
 104         platform_set_drvdata(pdev, NULL);
 105
 106         return 0;
 107 }
 108
 109 #ifdef CONFIG_PM
 110 static int atmel_trng_suspend(struct device *dev)
 111 {
 112         struct atmel_trng *trng = dev_get_drvdata(dev);
 113
 114         clk_disable(trng->clk);
 115
 116         return 0;
 117 }
 118
 119 static int atmel_trng_resume(struct device *dev)
 120 {
 121         struct atmel_trng *trng = dev_get_drvdata(dev);
 122
 123         return clk_enable(trng->clk);
 124 }
 125
 126 static const struct dev_pm_ops atmel_trng_pm_ops = {
 127         .suspend        = atmel_trng_suspend,
 128         .resume         = atmel_trng_resume,
 129 };
 130 #endif /* CONFIG_PM */
 131
 132 static struct platform_driver atmel_trng_driver = {
 133         .probe          = atmel_trng_probe,
 134         .remove         = __devexit_p(atmel_trng_remove),
 135         .driver         = {
 136                 .name   = "atmel-trng",
 137                 .owner  = THIS_MODULE,
 138 #ifdef CONFIG_PM
 139                 .pm     = &atmel_trng_pm_ops,
 140 #endif /* CONFIG_PM */
 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");