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/of_device.h>
  18 #include <linux/platform_device.h>
  19
  20 #define TRNG_CR         0x00
  21 #define TRNG_MR         0x04
  22 #define TRNG_ISR        0x1c
  23 #define TRNG_ODATA      0x50
  24
  25 #define TRNG_KEY        0x524e4700 /* RNG */
  26
  27 #define TRNG_HALFR      BIT(0) /* generate RN every 168 cycles */
  28
  29 struct atmel_trng_data {
  30         bool has_half_rate;
  31 };
  32
  33 struct atmel_trng {
  34         struct clk *clk;
  35         void __iomem *base;
  36         struct hwrng rng;
  37 };
  38
  39 static int atmel_trng_read(struct hwrng *rng, void *buf, size_t max,
  40                            bool wait)
  41 {
  42         struct atmel_trng *trng = container_of(rng, struct atmel_trng, rng);
  43         u32 *data = buf;
  44
  45         /* data ready? */
  46         if (readl(trng->base + TRNG_ISR) & 1) {
  47                 *data = readl(trng->base + TRNG_ODATA);
  48                 /*
  49                   ensure data ready is only set again AFTER the next data
  50                   word is ready in case it got set between checking ISR
  51                   and reading ODATA, so we don't risk re-reading the
  52                   same word
  53                 */
  54                 readl(trng->base + TRNG_ISR);
  55                 return 4;
  56         } else
  57                 return 0;
  58 }
  59
  60 static void atmel_trng_enable(struct atmel_trng *trng)
  61 {
  62         writel(TRNG_KEY | 1, trng->base + TRNG_CR);
  63 }
  64
  65 static void atmel_trng_disable(struct atmel_trng *trng)
  66 {
  67         writel(TRNG_KEY, trng->base + TRNG_CR);
  68 }
  69
  70 static int atmel_trng_probe(struct platform_device *pdev)
  71 {
  72         struct atmel_trng *trng;
  73         const struct atmel_trng_data *data;
  74         int ret;
  75
  76         trng = devm_kzalloc(&pdev->dev, sizeof(*trng), GFP_KERNEL);
  77         if (!trng)
  78                 return -ENOMEM;
  79
  80         trng->base = devm_platform_ioremap_resource(pdev, 0);
  81         if (IS_ERR(trng->base))
  82                 return PTR_ERR(trng->base);
  83
  84         trng->clk = devm_clk_get(&pdev->dev, NULL);
  85         if (IS_ERR(trng->clk))
  86                 return PTR_ERR(trng->clk);
  87         data = of_device_get_match_data(&pdev->dev);
  88         if (!data)
  89                 return -ENODEV;
  90
  91         if (data->has_half_rate) {
  92                 unsigned long rate = clk_get_rate(trng->clk);
  93
  94                 /* if peripheral clk is above 100MHz, set HALFR */
  95                 if (rate > 100000000)
  96                         writel(TRNG_HALFR, trng->base + TRNG_MR);
  97         }
  98
  99         ret = clk_prepare_enable(trng->clk);
 100         if (ret)
 101                 return ret;
 102
 103         atmel_trng_enable(trng);
 104         trng->rng.name = pdev->name;
 105         trng->rng.read = atmel_trng_read;
 106
 107         ret = devm_hwrng_register(&pdev->dev, &trng->rng);
 108         if (ret)
 109                 goto err_register;
 110
 111         platform_set_drvdata(pdev, trng);
 112
 113         return 0;
 114
 115 err_register:
 116         clk_disable_unprepare(trng->clk);
 117         return ret;
 118 }
 119
 120 static int atmel_trng_remove(struct platform_device *pdev)
 121 {
 122         struct atmel_trng *trng = platform_get_drvdata(pdev);
 123
 124
 125         atmel_trng_disable(trng);
 126         clk_disable_unprepare(trng->clk);
 127
 128         return 0;
 129 }
 130
 131 #ifdef CONFIG_PM
 132 static int atmel_trng_suspend(struct device *dev)
 133 {
 134         struct atmel_trng *trng = dev_get_drvdata(dev);
 135
 136         atmel_trng_disable(trng);
 137         clk_disable_unprepare(trng->clk);
 138
 139         return 0;
 140 }
 141
 142 static int atmel_trng_resume(struct device *dev)
 143 {
 144         struct atmel_trng *trng = dev_get_drvdata(dev);
 145         int ret;
 146
 147         ret = clk_prepare_enable(trng->clk);
 148         if (ret)
 149                 return ret;
 150
 151         atmel_trng_enable(trng);
 152
 153         return 0;
 154 }
 155
 156 static const struct dev_pm_ops atmel_trng_pm_ops = {
 157         .suspend        = atmel_trng_suspend,
 158         .resume         = atmel_trng_resume,
 159 };
 160 #endif /* CONFIG_PM */
 161
 162 static const struct atmel_trng_data at91sam9g45_config = {
 163         .has_half_rate = false,
 164 };
 165
 166 static const struct atmel_trng_data sam9x60_config = {
 167         .has_half_rate = true,
 168 };
 169
 170 static const struct of_device_id atmel_trng_dt_ids[] = {
 171         {
 172                 .compatible = "atmel,at91sam9g45-trng",
 173                 .data = &at91sam9g45_config,
 174         }, {
 175                 .compatible = "microchip,sam9x60-trng",
 176                 .data = &sam9x60_config,
 177         }, {
 178                 /* sentinel */
 179         }
 180 };
 181 MODULE_DEVICE_TABLE(of, atmel_trng_dt_ids);
 182
 183 static struct platform_driver atmel_trng_driver = {
 184         .probe          = atmel_trng_probe,
 185         .remove         = atmel_trng_remove,
 186         .driver         = {
 187                 .name   = "atmel-trng",
 188 #ifdef CONFIG_PM
 189                 .pm     = &atmel_trng_pm_ops,
 190 #endif /* CONFIG_PM */
 191                 .of_match_table = atmel_trng_dt_ids,
 192         },
 193 };
 194
 195 module_platform_driver(atmel_trng_driver);
 196
 197 MODULE_LICENSE("GPL");
 198 MODULE_AUTHOR("Peter Korsgaard <jacmet@sunsite.dk>");
 199 MODULE_DESCRIPTION("Atmel true random number generator driver");