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 static struct platform_device *rng_dev;
  63
  64 static int mxc_rnga_data_present(struct hwrng *rng, int wait)
  65 {
  66         void __iomem *rng_base = (void __iomem *)rng->priv;
  67         int i;
  68
  69         for (i = 0; i < 20; i++) {
  70                 /* how many random numbers are in FIFO? [0-16] */
  71                 int level = (__raw_readl(rng_base + RNGA_STATUS) &
  72                                 RNGA_STATUS_LEVEL_MASK) >> 8;
  73                 if (level || !wait)
  74                         return !!level;
  75                 udelay(10);
  76         }
  77         return 0;
  78 }
  79
  80 static int mxc_rnga_data_read(struct hwrng *rng, u32 * data)
  81 {
  82         int err;
  83         u32 ctrl;
  84         void __iomem *rng_base = (void __iomem *)rng->priv;
  85
  86         /* retrieve a random number from FIFO */
  87         *data = __raw_readl(rng_base + RNGA_OUTPUT_FIFO);
  88
  89         /* some error while reading this random number? */
  90         err = __raw_readl(rng_base + RNGA_STATUS) & RNGA_STATUS_ERROR_INT;
  91
  92         /* if error: clear error interrupt, but doesn't return random number */
  93         if (err) {
  94                 dev_dbg(&rng_dev->dev, "Error while reading random number!\n");
  95                 ctrl = __raw_readl(rng_base + RNGA_CONTROL);
  96                 __raw_writel(ctrl | RNGA_CONTROL_CLEAR_INT,
  97                                         rng_base + RNGA_CONTROL);
  98                 return 0;
  99         } else
 100                 return 4;
 101 }
 102
 103 static int mxc_rnga_init(struct hwrng *rng)
 104 {
 105         u32 ctrl, osc;
 106         void __iomem *rng_base = (void __iomem *)rng->priv;
 107
 108         /* wake up */
 109         ctrl = __raw_readl(rng_base + RNGA_CONTROL);
 110         __raw_writel(ctrl & ~RNGA_CONTROL_SLEEP, rng_base + RNGA_CONTROL);
 111
 112         /* verify if oscillator is working */
 113         osc = __raw_readl(rng_base + RNGA_STATUS);
 114         if (osc & RNGA_STATUS_OSC_DEAD) {
 115                 dev_err(&rng_dev->dev, "RNGA Oscillator is dead!\n");
 116                 return -ENODEV;
 117         }
 118
 119         /* go running */
 120         ctrl = __raw_readl(rng_base + RNGA_CONTROL);
 121         __raw_writel(ctrl | RNGA_CONTROL_GO, rng_base + RNGA_CONTROL);
 122
 123         return 0;
 124 }
 125
 126 static void mxc_rnga_cleanup(struct hwrng *rng)
 127 {
 128         u32 ctrl;
 129         void __iomem *rng_base = (void __iomem *)rng->priv;
 130
 131         ctrl = __raw_readl(rng_base + RNGA_CONTROL);
 132
 133         /* stop rnga */
 134         __raw_writel(ctrl & ~RNGA_CONTROL_GO, rng_base + RNGA_CONTROL);
 135 }
 136
 137 static struct hwrng mxc_rnga = {
 138         .name = "mxc-rnga",
 139         .init = mxc_rnga_init,
 140         .cleanup = mxc_rnga_cleanup,
 141         .data_present = mxc_rnga_data_present,
 142         .data_read = mxc_rnga_data_read
 143 };
 144
 145 static int __init mxc_rnga_probe(struct platform_device *pdev)
 146 {
 147         int err = -ENODEV;
 148         struct clk *clk;
 149         struct resource *res, *mem;
 150         void __iomem *rng_base = NULL;
 151
 152         if (rng_dev)
 153                 return -EBUSY;
 154
 155         clk = clk_get(&pdev->dev, NULL);
 156         if (IS_ERR(clk)) {
 157                 dev_err(&pdev->dev, "Could not get rng_clk!\n");
 158                 err = PTR_ERR(clk);
 159                 goto out;
 160         }
 161
 162         clk_prepare_enable(clk);
 163
 164         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 165         if (!res) {
 166                 err = -ENOENT;
 167                 goto err_region;
 168         }
 169
 170         mem = request_mem_region(res->start, resource_size(res), pdev->name);
 171         if (mem == NULL) {
 172                 err = -EBUSY;
 173                 goto err_region;
 174         }
 175
 176         rng_base = ioremap(res->start, resource_size(res));
 177         if (!rng_base) {
 178                 err = -ENOMEM;
 179                 goto err_ioremap;
 180         }
 181
 182         mxc_rnga.priv = (unsigned long)rng_base;
 183
 184         err = hwrng_register(&mxc_rnga);
 185         if (err) {
 186                 dev_err(&pdev->dev, "MXC RNGA registering failed (%d)\n", err);
 187                 goto err_register;
 188         }
 189
 190         rng_dev = pdev;
 191
 192         dev_info(&pdev->dev, "MXC RNGA Registered.\n");
 193
 194         return 0;
 195
 196 err_register:
 197         iounmap(rng_base);
 198         rng_base = NULL;
 199
 200 err_ioremap:
 201         release_mem_region(res->start, resource_size(res));
 202
 203 err_region:
 204         clk_disable_unprepare(clk);
 205         clk_put(clk);
 206
 207 out:
 208         return err;
 209 }
 210
 211 static int __exit mxc_rnga_remove(struct platform_device *pdev)
 212 {
 213         struct resource *res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 214         void __iomem *rng_base = (void __iomem *)mxc_rnga.priv;
 215         struct clk *clk = clk_get(&pdev->dev, NULL);
 216
 217         hwrng_unregister(&mxc_rnga);
 218
 219         iounmap(rng_base);
 220
 221         release_mem_region(res->start, resource_size(res));
 222
 223         clk_disable_unprepare(clk);
 224         clk_put(clk);
 225
 226         return 0;
 227 }
 228
 229 static struct platform_driver mxc_rnga_driver = {
 230         .driver = {
 231                    .name = "mxc_rnga",
 232                    .owner = THIS_MODULE,
 233                    },
 234         .remove = __exit_p(mxc_rnga_remove),
 235 };
 236
 237 static int __init mod_init(void)
 238 {
 239         return platform_driver_probe(&mxc_rnga_driver, mxc_rnga_probe);
 240 }
 241
 242 static void __exit mod_exit(void)
 243 {
 244         platform_driver_unregister(&mxc_rnga_driver);
 245 }
 246
 247 module_init(mod_init);
 248 module_exit(mod_exit);
 249
 250 MODULE_AUTHOR("Freescale Semiconductor, Inc.");
 251 MODULE_DESCRIPTION("H/W RNGA driver for i.MX");
 252 MODULE_LICENSE("GPL");