drivers/char/hw_random/exynos-rng.c

   1 /*
   2  * exynos-rng.c - Random Number Generator driver for the exynos
   3  *
   4  * Copyright (C) 2012 Samsung Electronics
   5  * Jonghwa Lee <jonghwa3.lee@smasung.com>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation;
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  19  *
  20  */
  21
  22 #include <linux/hw_random.h>
  23 #include <linux/kernel.h>
  24 #include <linux/module.h>
  25 #include <linux/init.h>
  26 #include <linux/io.h>
  27 #include <linux/platform_device.h>
  28 #include <linux/clk.h>
  29 #include <linux/pm_runtime.h>
  30 #include <linux/err.h>
  31
  32 #define EXYNOS_PRNG_STATUS_OFFSET       0x10
  33 #define EXYNOS_PRNG_SEED_OFFSET         0x140
  34 #define EXYNOS_PRNG_OUT1_OFFSET         0x160
  35 #define SEED_SETTING_DONE               BIT(1)
  36 #define PRNG_START                      0x18
  37 #define PRNG_DONE                       BIT(5)
  38 #define EXYNOS_AUTOSUSPEND_DELAY        100
  39
  40 struct exynos_rng {
  41         struct device *dev;
  42         struct hwrng rng;
  43         void __iomem *mem;
  44         struct clk *clk;
  45 };
  46
  47 static u32 exynos_rng_readl(struct exynos_rng *rng, u32 offset)
  48 {
  49         return  __raw_readl(rng->mem + offset);
  50 }
  51
  52 static void exynos_rng_writel(struct exynos_rng *rng, u32 val, u32 offset)
  53 {
  54         __raw_writel(val, rng->mem + offset);
  55 }
  56
  57 static int exynos_init(struct hwrng *rng)
  58 {
  59         struct exynos_rng *exynos_rng = container_of(rng,
  60                                                 struct exynos_rng, rng);
  61         int i;
  62         int ret = 0;
  63
  64         pm_runtime_get_sync(exynos_rng->dev);
  65
  66         for (i = 0 ; i < 5 ; i++)
  67                 exynos_rng_writel(exynos_rng, jiffies,
  68                                 EXYNOS_PRNG_SEED_OFFSET + 4*i);
  69
  70         if (!(exynos_rng_readl(exynos_rng, EXYNOS_PRNG_STATUS_OFFSET)
  71                                                  & SEED_SETTING_DONE))
  72                 ret = -EIO;
  73
  74         pm_runtime_put_noidle(exynos_rng->dev);
  75
  76         return ret;
  77 }
  78
  79 static int exynos_read(struct hwrng *rng, void *buf,
  80                                         size_t max, bool wait)
  81 {
  82         struct exynos_rng *exynos_rng = container_of(rng,
  83                                                 struct exynos_rng, rng);
  84         u32 *data = buf;
  85
  86         pm_runtime_get_sync(exynos_rng->dev);
  87
  88         exynos_rng_writel(exynos_rng, PRNG_START, 0);
  89
  90         while (!(exynos_rng_readl(exynos_rng,
  91                         EXYNOS_PRNG_STATUS_OFFSET) & PRNG_DONE))
  92                 cpu_relax();
  93
  94         exynos_rng_writel(exynos_rng, PRNG_DONE, EXYNOS_PRNG_STATUS_OFFSET);
  95
  96         *data = exynos_rng_readl(exynos_rng, EXYNOS_PRNG_OUT1_OFFSET);
  97
  98         pm_runtime_mark_last_busy(exynos_rng->dev);
  99         pm_runtime_autosuspend(exynos_rng->dev);
 100
 101         return 4;
 102 }
 103
 104 static int exynos_rng_probe(struct platform_device *pdev)
 105 {
 106         struct exynos_rng *exynos_rng;
 107         struct resource *res;
 108         int ret;
 109
 110         exynos_rng = devm_kzalloc(&pdev->dev, sizeof(struct exynos_rng),
 111                                         GFP_KERNEL);
 112         if (!exynos_rng)
 113                 return -ENOMEM;
 114
 115         exynos_rng->dev = &pdev->dev;
 116         exynos_rng->rng.name = "exynos";
 117         exynos_rng->rng.init =  exynos_init;
 118         exynos_rng->rng.read = exynos_read;
 119         exynos_rng->clk = devm_clk_get(&pdev->dev, "secss");
 120         if (IS_ERR(exynos_rng->clk)) {
 121                 dev_err(&pdev->dev, "Couldn't get clock.\n");
 122                 return -ENOENT;
 123         }
 124
 125         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 126         exynos_rng->mem = devm_ioremap_resource(&pdev->dev, res);
 127         if (IS_ERR(exynos_rng->mem))
 128                 return PTR_ERR(exynos_rng->mem);
 129
 130         platform_set_drvdata(pdev, exynos_rng);
 131
 132         pm_runtime_set_autosuspend_delay(&pdev->dev, EXYNOS_AUTOSUSPEND_DELAY);
 133         pm_runtime_use_autosuspend(&pdev->dev);
 134         pm_runtime_enable(&pdev->dev);
 135
 136         ret = hwrng_register(&exynos_rng->rng);
 137         if (ret) {
 138                 pm_runtime_dont_use_autosuspend(&pdev->dev);
 139                 pm_runtime_disable(&pdev->dev);
 140         }
 141
 142         return ret;
 143 }
 144
 145 static int exynos_rng_remove(struct platform_device *pdev)
 146 {
 147         struct exynos_rng *exynos_rng = platform_get_drvdata(pdev);
 148
 149         hwrng_unregister(&exynos_rng->rng);
 150
 151         return 0;
 152 }
 153
 154 #if defined(CONFIG_PM_SLEEP) || defined(CONFIG_PM_RUNTIME)
 155 static int exynos_rng_runtime_suspend(struct device *dev)
 156 {
 157         struct platform_device *pdev = to_platform_device(dev);
 158         struct exynos_rng *exynos_rng = platform_get_drvdata(pdev);
 159
 160         clk_disable_unprepare(exynos_rng->clk);
 161
 162         return 0;
 163 }
 164
 165 static int exynos_rng_runtime_resume(struct device *dev)
 166 {
 167         struct platform_device *pdev = to_platform_device(dev);
 168         struct exynos_rng *exynos_rng = platform_get_drvdata(pdev);
 169
 170         return clk_prepare_enable(exynos_rng->clk);
 171 }
 172 #endif
 173
 174 static UNIVERSAL_DEV_PM_OPS(exynos_rng_pm_ops, exynos_rng_runtime_suspend,
 175                                         exynos_rng_runtime_resume, NULL);
 176
 177 static struct platform_driver exynos_rng_driver = {
 178         .driver         = {
 179                 .name   = "exynos-rng",
 180                 .owner  = THIS_MODULE,
 181                 .pm     = &exynos_rng_pm_ops,
 182         },
 183         .probe          = exynos_rng_probe,
 184         .remove         = exynos_rng_remove,
 185 };
 186
 187 module_platform_driver(exynos_rng_driver);
 188
 189 MODULE_DESCRIPTION("EXYNOS 4 H/W Random Number Generator driver");
 190 MODULE_AUTHOR("Jonghwa Lee <jonghwa3.lee@samsung.com>");
 191 MODULE_LICENSE("GPL");