drivers/char/hw_random/omap-rng.c

   1 /*
   2  * drivers/char/hw_random/omap-rng.c
   3  *
   4  * RNG driver for TI OMAP CPU family
   5  *
   6  * Author: Deepak Saxena <dsaxena@plexity.net>
   7  *
   8  * Copyright 2005 (c) MontaVista Software, Inc.
   9  *
  10  * Mostly based on original driver:
  11  *
  12  * Copyright (C) 2005 Nokia Corporation
  13  * Author: Juha Yrjölä <juha.yrjola@nokia.com>
  14  *
  15  * This file is licensed under  the terms of the GNU General Public
  16  * License version 2. This program is licensed "as is" without any
  17  * warranty of any kind, whether express or implied.
  18  *
  19  * TODO:
  20  *
  21  * - Make status updated be interrupt driven so we don't poll
  22  *
  23  */
  24
  25 #include <linux/module.h>
  26 #include <linux/init.h>
  27 #include <linux/random.h>
  28 #include <linux/clk.h>
  29 #include <linux/err.h>
  30 #include <linux/platform_device.h>
  31 #include <linux/hw_random.h>
  32 #include <linux/delay.h>
  33
  34 #include <asm/io.h>
  35
  36 #define RNG_OUT_REG             0x00            /* Output register */
  37 #define RNG_STAT_REG            0x04            /* Status register
  38                                                         [0] = STAT_BUSY */
  39 #define RNG_ALARM_REG           0x24            /* Alarm register
  40                                                         [7:0] = ALARM_COUNTER */
  41 #define RNG_CONFIG_REG          0x28            /* Configuration register
  42                                                         [11:6] = RESET_COUNT
  43                                                         [5:3]  = RING2_DELAY
  44                                                         [2:0]  = RING1_DELAY */
  45 #define RNG_REV_REG             0x3c            /* Revision register
  46                                                         [7:0] = REV_NB */
  47 #define RNG_MASK_REG            0x40            /* Mask and reset register
  48                                                         [2] = IT_EN
  49                                                         [1] = SOFTRESET
  50                                                         [0] = AUTOIDLE */
  51 #define RNG_SYSSTATUS           0x44            /* System status
  52                                                         [0] = RESETDONE */
  53
  54 static void __iomem *rng_base;
  55 static struct clk *rng_ick;
  56 static struct platform_device *rng_dev;
  57
  58 static u32 omap_rng_read_reg(int reg)
  59 {
  60         return __raw_readl(rng_base + reg);
  61 }
  62
  63 static void omap_rng_write_reg(int reg, u32 val)
  64 {
  65         __raw_writel(val, rng_base + reg);
  66 }
  67
  68 /* REVISIT: Does the status bit really work on 16xx? */
  69 static int omap_rng_data_present(struct hwrng *rng, int wait)
  70 {
  71         int data, i;
  72
  73         for (i = 0; i < 20; i++) {
  74                 data = omap_rng_read_reg(RNG_STAT_REG) ? 0 : 1;
  75                 if (data || !wait)
  76                         break;
  77                 udelay(10);
  78         }
  79         return data;
  80 }
  81
  82 static int omap_rng_data_read(struct hwrng *rng, u32 *data)
  83 {
  84         *data = omap_rng_read_reg(RNG_OUT_REG);
  85
  86         return 4;
  87 }
  88
  89 static struct hwrng omap_rng_ops = {
  90         .name           = "omap",
  91         .data_present   = omap_rng_data_present,
  92         .data_read      = omap_rng_data_read,
  93 };
  94
  95 static int __init omap_rng_probe(struct platform_device *pdev)
  96 {
  97         struct resource *res, *mem;
  98         int ret;
  99
 100         /*
 101          * A bit ugly, and it will never actually happen but there can
 102          * be only one RNG and this catches any bork
 103          */
 104         BUG_ON(rng_dev);
 105
 106         if (cpu_is_omap24xx()) {
 107                 rng_ick = clk_get(NULL, "rng_ick");
 108                 if (IS_ERR(rng_ick)) {
 109                         dev_err(&pdev->dev, "Could not get rng_ick\n");
 110                         ret = PTR_ERR(rng_ick);
 111                         return ret;
 112                 } else
 113                         clk_enable(rng_ick);
 114         }
 115
 116         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 117
 118         if (!res)
 119                 return -ENOENT;
 120
 121         mem = request_mem_region(res->start, res->end - res->start + 1,
 122                                  pdev->name);
 123         if (mem == NULL)
 124                 return -EBUSY;
 125
 126         dev_set_drvdata(&pdev->dev, mem);
 127         rng_base = (u32 __iomem *)io_p2v(res->start);
 128
 129         ret = hwrng_register(&omap_rng_ops);
 130         if (ret) {
 131                 release_resource(mem);
 132                 rng_base = NULL;
 133                 return ret;
 134         }
 135
 136         dev_info(&pdev->dev, "OMAP Random Number Generator ver. %02x\n",
 137                 omap_rng_read_reg(RNG_REV_REG));
 138         omap_rng_write_reg(RNG_MASK_REG, 0x1);
 139
 140         rng_dev = pdev;
 141
 142         return 0;
 143 }
 144
 145 static int __exit omap_rng_remove(struct platform_device *pdev)
 146 {
 147         struct resource *mem = dev_get_drvdata(&pdev->dev);
 148
 149         hwrng_unregister(&omap_rng_ops);
 150
 151         omap_rng_write_reg(RNG_MASK_REG, 0x0);
 152
 153         if (cpu_is_omap24xx()) {
 154                 clk_disable(rng_ick);
 155                 clk_put(rng_ick);
 156         }
 157
 158         release_resource(mem);
 159         rng_base = NULL;
 160
 161         return 0;
 162 }
 163
 164 #ifdef CONFIG_PM
 165
 166 static int omap_rng_suspend(struct platform_device *pdev, pm_message_t message)
 167 {
 168         omap_rng_write_reg(RNG_MASK_REG, 0x0);
 169         return 0;
 170 }
 171
 172 static int omap_rng_resume(struct platform_device *pdev)
 173 {
 174         omap_rng_write_reg(RNG_MASK_REG, 0x1);
 175         return 0;
 176 }
 177
 178 #else
 179
 180 #define omap_rng_suspend        NULL
 181 #define omap_rng_resume         NULL
 182
 183 #endif
 184
 185
 186 static struct platform_driver omap_rng_driver = {
 187         .driver = {
 188                 .name           = "omap_rng",
 189                 .owner          = THIS_MODULE,
 190         },
 191         .probe          = omap_rng_probe,
 192         .remove         = __exit_p(omap_rng_remove),
 193         .suspend        = omap_rng_suspend,
 194         .resume         = omap_rng_resume
 195 };
 196
 197 static int __init omap_rng_init(void)
 198 {
 199         if (!cpu_is_omap16xx() && !cpu_is_omap24xx())
 200                 return -ENODEV;
 201
 202         return platform_driver_register(&omap_rng_driver);
 203 }
 204
 205 static void __exit omap_rng_exit(void)
 206 {
 207         platform_driver_unregister(&omap_rng_driver);
 208 }
 209
 210 module_init(omap_rng_init);
 211 module_exit(omap_rng_exit);
 212
 213 MODULE_AUTHOR("Deepak Saxena (and others)");
 214 MODULE_LICENSE("GPL");