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 void atmel_trng_enable(struct atmel_trng *trng)
  52 {
  53         writel(TRNG_KEY | 1, trng->base + TRNG_CR);
  54 }
  55
  56 static void atmel_trng_disable(struct atmel_trng *trng)
  57 {
  58         writel(TRNG_KEY, trng->base + TRNG_CR);
  59 }
  60
  61 static int atmel_trng_probe(struct platform_device *pdev)
  62 {
  63         struct atmel_trng *trng;
  64         struct resource *res;
  65         int ret;
  66
  67         trng = devm_kzalloc(&pdev->dev, sizeof(*trng), GFP_KERNEL);
  68         if (!trng)
  69                 return -ENOMEM;
  70
  71         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  72         trng->base = devm_ioremap_resource(&pdev->dev, res);
  73         if (IS_ERR(trng->base))
  74                 return PTR_ERR(trng->base);
  75
  76         trng->clk = devm_clk_get(&pdev->dev, NULL);
  77         if (IS_ERR(trng->clk))
  78                 return PTR_ERR(trng->clk);
  79
  80         ret = clk_prepare_enable(trng->clk);
  81         if (ret)
  82                 return ret;
  83
  84         atmel_trng_enable(trng);
  85         trng->rng.name = pdev->name;
  86         trng->rng.read = atmel_trng_read;
  87
  88         ret = hwrng_register(&trng->rng);
  89         if (ret)
  90                 goto err_register;
  91
  92         platform_set_drvdata(pdev, trng);
  93
  94         return 0;
  95
  96 err_register:
  97         clk_disable_unprepare(trng->clk);
  98         return ret;
  99 }
 100
 101 static int 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         atmel_trng_disable(trng);
 108         clk_disable_unprepare(trng->clk);
 109
 110         return 0;
 111 }
 112
 113 #ifdef CONFIG_PM
 114 static int atmel_trng_suspend(struct device *dev)
 115 {
 116         struct atmel_trng *trng = dev_get_drvdata(dev);
 117
 118         atmel_trng_disable(trng);
 119         clk_disable_unprepare(trng->clk);
 120
 121         return 0;
 122 }
 123
 124 static int atmel_trng_resume(struct device *dev)
 125 {
 126         struct atmel_trng *trng = dev_get_drvdata(dev);
 127         int ret;
 128
 129         ret = clk_prepare_enable(trng->clk);
 130         if (ret)
 131                 return ret;
 132
 133         atmel_trng_enable(trng);
 134
 135         return 0;
 136 }
 137
 138 static const struct dev_pm_ops atmel_trng_pm_ops = {
 139         .suspend        = atmel_trng_suspend,
 140         .resume         = atmel_trng_resume,
 141 };
 142 #endif /* CONFIG_PM */
 143
 144 static const struct of_device_id atmel_trng_dt_ids[] = {
 145         { .compatible = "atmel,at91sam9g45-trng" },
 146         { /* sentinel */ }
 147 };
 148 MODULE_DEVICE_TABLE(of, atmel_trng_dt_ids);
 149
 150 static struct platform_driver atmel_trng_driver = {
 151         .probe          = atmel_trng_probe,
 152         .remove         = atmel_trng_remove,
 153         .driver         = {
 154                 .name   = "atmel-trng",
 155 #ifdef CONFIG_PM
 156                 .pm     = &atmel_trng_pm_ops,
 157 #endif /* CONFIG_PM */
 158                 .of_match_table = atmel_trng_dt_ids,
 159         },
 160 };
 161
 162 module_platform_driver(atmel_trng_driver);
 163
 164 MODULE_LICENSE("GPL");
 165 MODULE_AUTHOR("Peter Korsgaard <jacmet@sunsite.dk>");
 166 MODULE_DESCRIPTION("Atmel true random number generator driver");