drivers/char/hw_random/mxc-rnga.c

   1 /*
   2  * RNG driver for Freescale RNGA
   3  *
   4  * Copyright 2008-2009 Freescale Semiconductor, Inc. All Rights Reserved.
   5  * Author: Alan Carvalho de Assis <acassis@gmail.com>
   6  */
   7
   8 /*
   9  * The code contained herein is licensed under the GNU General Public
  10  * License. You may obtain a copy of the GNU General Public License
  11  * Version 2 or later at the following locations:
  12  *
  13  * http://www.opensource.org/licenses/gpl-license.html
  14  * http://www.gnu.org/copyleft/gpl.html
  15  *
  16  * This driver is based on other RNG drivers.
  17  */
  18
  19 #include <linux/module.h>
  20 #include <linux/init.h>
  21 #include <linux/kernel.h>
  22 #include <linux/clk.h>
  23 #include <linux/err.h>
  24 #include <linux/ioport.h>
  25 #include <linux/platform_device.h>
  26 #include <linux/hw_random.h>
  27 #include <linux/delay.h>
  28 #include <linux/io.h>
  29
  30 /* RNGA Registers */
  31 #define RNGA_CONTROL                    0x00
  32 #define RNGA_STATUS                     0x04
  33 #define RNGA_ENTROPY                    0x08
  34 #define RNGA_OUTPUT_FIFO                0x0c
  35 #define RNGA_MODE                       0x10
  36 #define RNGA_VERIFICATION_CONTROL       0x14
  37 #define RNGA_OSC_CONTROL_COUNTER        0x18
  38 #define RNGA_OSC1_COUNTER               0x1c
  39 #define RNGA_OSC2_COUNTER               0x20
  40 #define RNGA_OSC_COUNTER_STATUS         0x24
  41
  42 /* RNGA Registers Range */
  43 #define RNG_ADDR_RANGE                  0x28
  44
  45 /* RNGA Control Register */
  46 #define RNGA_CONTROL_SLEEP              0x00000010
  47 #define RNGA_CONTROL_CLEAR_INT          0x00000008
  48 #define RNGA_CONTROL_MASK_INTS          0x00000004
  49 #define RNGA_CONTROL_HIGH_ASSURANCE     0x00000002
  50 #define RNGA_CONTROL_GO                 0x00000001
  51
  52 #define RNGA_STATUS_LEVEL_MASK          0x0000ff00
  53
  54 /* RNGA Status Register */
  55 #define RNGA_STATUS_OSC_DEAD            0x80000000
  56 #define RNGA_STATUS_SLEEP               0x00000010
  57 #define RNGA_STATUS_ERROR_INT           0x00000008
  58 #define RNGA_STATUS_FIFO_UNDERFLOW      0x00000004
  59 #define RNGA_STATUS_LAST_READ_STATUS    0x00000002
  60 #define RNGA_STATUS_SECURITY_VIOLATION  0x00000001
  61
  62 struct mxc_rng {
  63         struct device *dev;
  64         struct hwrng rng;
  65         void __iomem *mem;
  66         struct clk *clk;
  67 };
  68
  69 static int mxc_rnga_data_present(struct hwrng *rng, int wait)
  70 {
  71         int i;
  72         struct mxc_rng *mxc_rng = container_of(rng, struct mxc_rng, rng);
  73
  74         for (i = 0; i < 20; i++) {
  75                 /* how many random numbers are in FIFO? [0-16] */
  76                 int level = (__raw_readl(mxc_rng->mem + RNGA_STATUS) &
  77                                 RNGA_STATUS_LEVEL_MASK) >> 8;
  78                 if (level || !wait)
  79                         return !!level;
  80                 udelay(10);
  81         }
  82         return 0;
  83 }
  84
  85 static int mxc_rnga_data_read(struct hwrng *rng, u32 * data)
  86 {
  87         int err;
  88         u32 ctrl;
  89         struct mxc_rng *mxc_rng = container_of(rng, struct mxc_rng, rng);
  90
  91         /* retrieve a random number from FIFO */
  92         *data = __raw_readl(mxc_rng->mem + RNGA_OUTPUT_FIFO);
  93
  94         /* some error while reading this random number? */
  95         err = __raw_readl(mxc_rng->mem + RNGA_STATUS) & RNGA_STATUS_ERROR_INT;
  96
  97         /* if error: clear error interrupt, but doesn't return random number */
  98         if (err) {
  99                 dev_dbg(mxc_rng->dev, "Error while reading random number!\n");
 100                 ctrl = __raw_readl(mxc_rng->mem + RNGA_CONTROL);
 101                 __raw_writel(ctrl | RNGA_CONTROL_CLEAR_INT,
 102                                         mxc_rng->mem + RNGA_CONTROL);
 103                 return 0;
 104         } else
 105                 return 4;
 106 }
 107
 108 static int mxc_rnga_init(struct hwrng *rng)
 109 {
 110         u32 ctrl, osc;
 111         struct mxc_rng *mxc_rng = container_of(rng, struct mxc_rng, rng);
 112
 113         /* wake up */
 114         ctrl = __raw_readl(mxc_rng->mem + RNGA_CONTROL);
 115         __raw_writel(ctrl & ~RNGA_CONTROL_SLEEP, mxc_rng->mem + RNGA_CONTROL);
 116
 117         /* verify if oscillator is working */
 118         osc = __raw_readl(mxc_rng->mem + RNGA_STATUS);
 119         if (osc & RNGA_STATUS_OSC_DEAD) {
 120                 dev_err(mxc_rng->dev, "RNGA Oscillator is dead!\n");
 121                 return -ENODEV;
 122         }
 123
 124         /* go running */
 125         ctrl = __raw_readl(mxc_rng->mem + RNGA_CONTROL);
 126         __raw_writel(ctrl | RNGA_CONTROL_GO, mxc_rng->mem + RNGA_CONTROL);
 127
 128         return 0;
 129 }
 130
 131 static void mxc_rnga_cleanup(struct hwrng *rng)
 132 {
 133         u32 ctrl;
 134         struct mxc_rng *mxc_rng = container_of(rng, struct mxc_rng, rng);
 135
 136         ctrl = __raw_readl(mxc_rng->mem + RNGA_CONTROL);
 137
 138         /* stop rnga */
 139         __raw_writel(ctrl & ~RNGA_CONTROL_GO, mxc_rng->mem + RNGA_CONTROL);
 140 }
 141
 142 static int __init mxc_rnga_probe(struct platform_device *pdev)
 143 {
 144         int err;
 145         struct resource *res;
 146         struct mxc_rng *mxc_rng;
 147
 148         mxc_rng = devm_kzalloc(&pdev->dev, sizeof(*mxc_rng), GFP_KERNEL);
 149         if (!mxc_rng)
 150                 return -ENOMEM;
 151
 152         mxc_rng->dev = &pdev->dev;
 153         mxc_rng->rng.name = "mxc-rnga";
 154         mxc_rng->rng.init = mxc_rnga_init;
 155         mxc_rng->rng.cleanup = mxc_rnga_cleanup,
 156         mxc_rng->rng.data_present = mxc_rnga_data_present,
 157         mxc_rng->rng.data_read = mxc_rnga_data_read,
 158
 159         mxc_rng->clk = devm_clk_get(&pdev->dev, NULL);
 160         if (IS_ERR(mxc_rng->clk)) {
 161                 dev_err(&pdev->dev, "Could not get rng_clk!\n");
 162                 return PTR_ERR(mxc_rng->clk);
 163         }
 164
 165         err = clk_prepare_enable(mxc_rng->clk);
 166         if (err)
 167                 return err;
 168
 169         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 170         mxc_rng->mem = devm_ioremap_resource(&pdev->dev, res);
 171         if (IS_ERR(mxc_rng->mem)) {
 172                 err = PTR_ERR(mxc_rng->mem);
 173                 goto err_ioremap;
 174         }
 175
 176         err = hwrng_register(&mxc_rng->rng);
 177         if (err) {
 178                 dev_err(&pdev->dev, "MXC RNGA registering failed (%d)\n", err);
 179                 goto err_ioremap;
 180         }
 181
 182         return 0;
 183
 184 err_ioremap:
 185         clk_disable_unprepare(mxc_rng->clk);
 186         return err;
 187 }
 188
 189 static int __exit mxc_rnga_remove(struct platform_device *pdev)
 190 {
 191         struct mxc_rng *mxc_rng = platform_get_drvdata(pdev);
 192
 193         hwrng_unregister(&mxc_rng->rng);
 194
 195         clk_disable_unprepare(mxc_rng->clk);
 196
 197         return 0;
 198 }
 199
 200 static struct platform_driver mxc_rnga_driver = {
 201         .driver = {
 202                    .name = "mxc_rnga",
 203                    },
 204         .remove = __exit_p(mxc_rnga_remove),
 205 };
 206
 207 module_platform_driver_probe(mxc_rnga_driver, mxc_rnga_probe);
 208
 209 MODULE_AUTHOR("Freescale Semiconductor, Inc.");
 210 MODULE_DESCRIPTION("H/W RNGA driver for i.MX");
 211 MODULE_LICENSE("GPL");