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/io.h>
  26 #include <linux/platform_device.h>
  27 #include <linux/clk.h>
  28 #include <linux/pm_runtime.h>
  29 #include <linux/err.h>
  30
  31 #define EXYNOS_PRNG_STATUS_OFFSET       0x10
  32 #define EXYNOS_PRNG_SEED_OFFSET         0x140
  33 #define EXYNOS_PRNG_OUT1_OFFSET         0x160
  34 #define SEED_SETTING_DONE               BIT(1)
  35 #define PRNG_START                      0x18
  36 #define PRNG_DONE                       BIT(5)
  37 #define EXYNOS_AUTOSUSPEND_DELAY        100
  38
  39 struct exynos_rng {
  40         struct device *dev;
  41         struct hwrng rng;
  42         void __iomem *mem;
  43         struct clk *clk;
  44 };
  45
  46 static u32 exynos_rng_readl(struct exynos_rng *rng, u32 offset)
  47 {
  48         return  __raw_readl(rng->mem + offset);
  49 }
  50
  51 static void exynos_rng_writel(struct exynos_rng *rng, u32 val, u32 offset)
  52 {
  53         __raw_writel(val, rng->mem + offset);
  54 }
  55
  56 static int exynos_init(struct hwrng *rng)
  57 {
  58         struct exynos_rng *exynos_rng = container_of(rng,
  59                                                 struct exynos_rng, rng);
  60         int i;
  61         int ret = 0;
  62
  63         pm_runtime_get_sync(exynos_rng->dev);
  64
  65         for (i = 0 ; i < 5 ; i++)
  66                 exynos_rng_writel(exynos_rng, jiffies,
  67                                 EXYNOS_PRNG_SEED_OFFSET + 4*i);
  68
  69         if (!(exynos_rng_readl(exynos_rng, EXYNOS_PRNG_STATUS_OFFSET)
  70                                                  & SEED_SETTING_DONE))
  71                 ret = -EIO;
  72
  73         pm_runtime_put_noidle(exynos_rng->dev);
  74
  75         return ret;
  76 }
  77
  78 static int exynos_read(struct hwrng *rng, void *buf,
  79                                         size_t max, bool wait)
  80 {
  81         struct exynos_rng *exynos_rng = container_of(rng,
  82                                                 struct exynos_rng, rng);
  83         u32 *data = buf;
  84
  85         pm_runtime_get_sync(exynos_rng->dev);
  86
  87         exynos_rng_writel(exynos_rng, PRNG_START, 0);
  88
  89         while (!(exynos_rng_readl(exynos_rng,
  90                         EXYNOS_PRNG_STATUS_OFFSET) & PRNG_DONE))
  91                 cpu_relax();
  92
  93         exynos_rng_writel(exynos_rng, PRNG_DONE, EXYNOS_PRNG_STATUS_OFFSET);
  94
  95         *data = exynos_rng_readl(exynos_rng, EXYNOS_PRNG_OUT1_OFFSET);
  96
  97         pm_runtime_mark_last_busy(exynos_rng->dev);
  98         pm_runtime_autosuspend(exynos_rng->dev);
  99
 100         return 4;
 101 }
 102
 103 static int exynos_rng_probe(struct platform_device *pdev)
 104 {
 105         struct exynos_rng *exynos_rng;
 106         struct resource *res;
 107
 108         exynos_rng = devm_kzalloc(&pdev->dev, sizeof(struct exynos_rng),
 109                                         GFP_KERNEL);
 110         if (!exynos_rng)
 111                 return -ENOMEM;
 112
 113         exynos_rng->dev = &pdev->dev;
 114         exynos_rng->rng.name = "exynos";
 115         exynos_rng->rng.init =  exynos_init;
 116         exynos_rng->rng.read = exynos_read;
 117         exynos_rng->clk = devm_clk_get(&pdev->dev, "secss");
 118         if (IS_ERR(exynos_rng->clk)) {
 119                 dev_err(&pdev->dev, "Couldn't get clock.\n");
 120                 return -ENOENT;
 121         }
 122
 123         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 124         exynos_rng->mem = devm_ioremap_resource(&pdev->dev, res);
 125         if (IS_ERR(exynos_rng->mem))
 126                 return PTR_ERR(exynos_rng->mem);
 127
 128         platform_set_drvdata(pdev, exynos_rng);
 129
 130         pm_runtime_set_autosuspend_delay(&pdev->dev, EXYNOS_AUTOSUSPEND_DELAY);
 131         pm_runtime_use_autosuspend(&pdev->dev);
 132         pm_runtime_enable(&pdev->dev);
 133
 134         return devm_hwrng_register(&pdev->dev, &exynos_rng->rng);
 135 }
 136
 137 #ifdef CONFIG_PM
 138 static int exynos_rng_runtime_suspend(struct device *dev)
 139 {
 140         struct platform_device *pdev = to_platform_device(dev);
 141         struct exynos_rng *exynos_rng = platform_get_drvdata(pdev);
 142
 143         clk_disable_unprepare(exynos_rng->clk);
 144
 145         return 0;
 146 }
 147
 148 static int exynos_rng_runtime_resume(struct device *dev)
 149 {
 150         struct platform_device *pdev = to_platform_device(dev);
 151         struct exynos_rng *exynos_rng = platform_get_drvdata(pdev);
 152
 153         return clk_prepare_enable(exynos_rng->clk);
 154 }
 155 #endif
 156
 157 static UNIVERSAL_DEV_PM_OPS(exynos_rng_pm_ops, exynos_rng_runtime_suspend,
 158                                         exynos_rng_runtime_resume, NULL);
 159
 160 static struct platform_driver exynos_rng_driver = {
 161         .driver         = {
 162                 .name   = "exynos-rng",
 163                 .pm     = &exynos_rng_pm_ops,
 164         },
 165         .probe          = exynos_rng_probe,
 166 };
 167
 168 module_platform_driver(exynos_rng_driver);
 169
 170 MODULE_DESCRIPTION("EXYNOS 4 H/W Random Number Generator driver");
 171 MODULE_AUTHOR("Jonghwa Lee <jonghwa3.lee@samsung.com>");
 172 MODULE_LICENSE("GPL");