drivers/char/hw_random/omap-rng.c

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