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/mod_devicetable.h>
  12 #include <linux/slab.h>
  13 #include <linux/err.h>
  14 #include <linux/clk.h>
  15 #include <linux/io.h>
  16 #include <linux/hw_random.h>
  17 #include <linux/platform_device.h>
  18
  19 #define TRNG_CR         0x00
  20 #define TRNG_ISR        0x1c
  21 #define TRNG_ODATA      0x50
  22
  23 #define TRNG_KEY        0x524e4700 /* RNG */
  24
  25 struct atmel_trng {
  26         struct clk *clk;
  27         void __iomem *base;
  28         struct hwrng rng;
  29 };
  30
  31 static int atmel_trng_read(struct hwrng *rng, void *buf, size_t max,
  32                            bool wait)
  33 {
  34         struct atmel_trng *trng = container_of(rng, struct atmel_trng, rng);
  35         u32 *data = buf;
  36
  37         /* data ready? */
  38         if (readl(trng->base + TRNG_ISR) & 1) {
  39                 *data = readl(trng->base + TRNG_ODATA);
  40                 /*
  41                   ensure data ready is only set again AFTER the next data
  42                   word is ready in case it got set between checking ISR
  43                   and reading ODATA, so we don't risk re-reading the
  44                   same word
  45                 */
  46                 readl(trng->base + TRNG_ISR);
  47                 return 4;
  48         } else
  49                 return 0;
  50 }
  51
  52 static void atmel_trng_enable(struct atmel_trng *trng)
  53 {
  54         writel(TRNG_KEY | 1, trng->base + TRNG_CR);
  55 }
  56
  57 static void atmel_trng_disable(struct atmel_trng *trng)
  58 {
  59         writel(TRNG_KEY, trng->base + TRNG_CR);
  60 }
  61
  62 static int atmel_trng_probe(struct platform_device *pdev)
  63 {
  64         struct atmel_trng *trng;
  65         struct resource *res;
  66         int ret;
  67
  68         trng = devm_kzalloc(&pdev->dev, sizeof(*trng), GFP_KERNEL);
  69         if (!trng)
  70                 return -ENOMEM;
  71
  72         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  73         trng->base = devm_ioremap_resource(&pdev->dev, res);
  74         if (IS_ERR(trng->base))
  75                 return PTR_ERR(trng->base);
  76
  77         trng->clk = devm_clk_get(&pdev->dev, NULL);
  78         if (IS_ERR(trng->clk))
  79                 return PTR_ERR(trng->clk);
  80
  81         ret = clk_prepare_enable(trng->clk);
  82         if (ret)
  83                 return ret;
  84
  85         atmel_trng_enable(trng);
  86         trng->rng.name = pdev->name;
  87         trng->rng.read = atmel_trng_read;
  88
  89         ret = hwrng_register(&trng->rng);
  90         if (ret)
  91                 goto err_register;
  92
  93         platform_set_drvdata(pdev, trng);
  94
  95         return 0;
  96
  97 err_register:
  98         clk_disable_unprepare(trng->clk);
  99         return ret;
 100 }
 101
 102 static int atmel_trng_remove(struct platform_device *pdev)
 103 {
 104         struct atmel_trng *trng = platform_get_drvdata(pdev);
 105
 106         hwrng_unregister(&trng->rng);
 107
 108         atmel_trng_disable(trng);
 109         clk_disable_unprepare(trng->clk);
 110
 111         return 0;
 112 }
 113
 114 #ifdef CONFIG_PM
 115 static int atmel_trng_suspend(struct device *dev)
 116 {
 117         struct atmel_trng *trng = dev_get_drvdata(dev);
 118
 119         atmel_trng_disable(trng);
 120         clk_disable_unprepare(trng->clk);
 121
 122         return 0;
 123 }
 124
 125 static int atmel_trng_resume(struct device *dev)
 126 {
 127         struct atmel_trng *trng = dev_get_drvdata(dev);
 128         int ret;
 129
 130         ret = clk_prepare_enable(trng->clk);
 131         if (ret)
 132                 return ret;
 133
 134         atmel_trng_enable(trng);
 135
 136         return 0;
 137 }
 138
 139 static const struct dev_pm_ops atmel_trng_pm_ops = {
 140         .suspend        = atmel_trng_suspend,
 141         .resume         = atmel_trng_resume,
 142 };
 143 #endif /* CONFIG_PM */
 144
 145 static const struct of_device_id atmel_trng_dt_ids[] = {
 146         { .compatible = "atmel,at91sam9g45-trng" },
 147         { /* sentinel */ }
 148 };
 149 MODULE_DEVICE_TABLE(of, atmel_trng_dt_ids);
 150
 151 static struct platform_driver atmel_trng_driver = {
 152         .probe          = atmel_trng_probe,
 153         .remove         = atmel_trng_remove,
 154         .driver         = {
 155                 .name   = "atmel-trng",
 156 #ifdef CONFIG_PM
 157                 .pm     = &atmel_trng_pm_ops,
 158 #endif /* CONFIG_PM */
 159                 .of_match_table = atmel_trng_dt_ids,
 160         },
 161 };
 162
 163 module_platform_driver(atmel_trng_driver);
 164
 165 MODULE_LICENSE("GPL");
 166 MODULE_AUTHOR("Peter Korsgaard <jacmet@sunsite.dk>");
 167 MODULE_DESCRIPTION("Atmel true random number generator driver");