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         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");