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_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         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  58         if (!res)
  59                 return -EINVAL;
  60
  61         trng = devm_kzalloc(&pdev->dev, sizeof(*trng), GFP_KERNEL);
  62         if (!trng)
  63                 return -ENOMEM;
  64
  65         if (!devm_request_mem_region(&pdev->dev, res->start,
  66                                      resource_size(res), pdev->name))
  67                 return -EBUSY;
  68
  69         trng->base = devm_ioremap(&pdev->dev, res->start, resource_size(res));
  70         if (!trng->base)
  71                 return -EBUSY;
  72
  73         trng->clk = clk_get(&pdev->dev, NULL);
  74         if (IS_ERR(trng->clk))
  75                 return PTR_ERR(trng->clk);
  76
  77         ret = clk_enable(trng->clk);
  78         if (ret)
  79                 goto err_enable;
  80
  81         writel(TRNG_KEY | 1, trng->base + TRNG_CR);
  82         trng->rng.name = pdev->name;
  83         trng->rng.read = atmel_trng_read;
  84
  85         ret = hwrng_register(&trng->rng);
  86         if (ret)
  87                 goto err_register;
  88
  89         platform_set_drvdata(pdev, trng);
  90
  91         return 0;
  92
  93 err_register:
  94         clk_disable(trng->clk);
  95 err_enable:
  96         clk_put(trng->clk);
  97
  98         return ret;
  99 }
 100
 101 static int __devexit atmel_trng_remove(struct platform_device *pdev)
 102 {
 103         struct atmel_trng *trng = platform_get_drvdata(pdev);
 104
 105         hwrng_unregister(&trng->rng);
 106
 107         writel(TRNG_KEY, trng->base + TRNG_CR);
 108         clk_disable(trng->clk);
 109         clk_put(trng->clk);
 110
 111         platform_set_drvdata(pdev, NULL);
 112
 113         return 0;
 114 }
 115
 116 #ifdef CONFIG_PM
 117 static int atmel_trng_suspend(struct device *dev)
 118 {
 119         struct atmel_trng *trng = dev_get_drvdata(dev);
 120
 121         clk_disable(trng->clk);
 122
 123         return 0;
 124 }
 125
 126 static int atmel_trng_resume(struct device *dev)
 127 {
 128         struct atmel_trng *trng = dev_get_drvdata(dev);
 129
 130         return clk_enable(trng->clk);
 131 }
 132
 133 static const struct dev_pm_ops atmel_trng_pm_ops = {
 134         .suspend        = atmel_trng_suspend,
 135         .resume         = atmel_trng_resume,
 136 };
 137 #endif /* CONFIG_PM */
 138
 139 static struct platform_driver atmel_trng_driver = {
 140         .probe          = atmel_trng_probe,
 141         .remove         = __devexit_p(atmel_trng_remove),
 142         .driver         = {
 143                 .name   = "atmel-trng",
 144                 .owner  = THIS_MODULE,
 145 #ifdef CONFIG_PM
 146                 .pm     = &atmel_trng_pm_ops,
 147 #endif /* CONFIG_PM */
 148         },
 149 };
 150
 151 module_platform_driver(atmel_trng_driver);
 152
 153 MODULE_LICENSE("GPL");
 154 MODULE_AUTHOR("Peter Korsgaard <jacmet@sunsite.dk>");
 155 MODULE_DESCRIPTION("Atmel true random number generator driver");