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 #include <plat/cpu.h>
  30
  31 #define RNG_OUT_REG             0x00            /* Output register */
  32 #define RNG_STAT_REG            0x04            /* Status register
  33                                                         [0] = STAT_BUSY */
  34 #define RNG_ALARM_REG           0x24            /* Alarm register
  35                                                         [7:0] = ALARM_COUNTER */
  36 #define RNG_CONFIG_REG          0x28            /* Configuration register
  37                                                         [11:6] = RESET_COUNT
  38                                                         [5:3]  = RING2_DELAY
  39                                                         [2:0]  = RING1_DELAY */
  40 #define RNG_REV_REG             0x3c            /* Revision register
  41                                                         [7:0] = REV_NB */
  42 #define RNG_MASK_REG            0x40            /* Mask and reset register
  43                                                         [2] = IT_EN
  44                                                         [1] = SOFTRESET
  45                                                         [0] = AUTOIDLE */
  46 #define RNG_SYSSTATUS           0x44            /* System status
  47                                                         [0] = RESETDONE */
  48
  49 static void __iomem *rng_base;
  50 static struct clk *rng_ick;
  51 static struct platform_device *rng_dev;
  52
  53 static inline u32 omap_rng_read_reg(int reg)
  54 {
  55         return __raw_readl(rng_base + reg);
  56 }
  57
  58 static inline void omap_rng_write_reg(int reg, u32 val)
  59 {
  60         __raw_writel(val, rng_base + reg);
  61 }
  62
  63 static int omap_rng_data_present(struct hwrng *rng, int wait)
  64 {
  65         int data, i;
  66
  67         for (i = 0; i < 20; i++) {
  68                 data = omap_rng_read_reg(RNG_STAT_REG) ? 0 : 1;
  69                 if (data || !wait)
  70                         break;
  71                 /* RNG produces data fast enough (2+ MBit/sec, even
  72                  * during "rngtest" loads, that these delays don't
  73                  * seem to trigger.  We *could* use the RNG IRQ, but
  74                  * that'd be higher overhead ... so why bother?
  75                  */
  76                 udelay(10);
  77         }
  78         return data;
  79 }
  80
  81 static int omap_rng_data_read(struct hwrng *rng, u32 *data)
  82 {
  83         *data = omap_rng_read_reg(RNG_OUT_REG);
  84
  85         return 4;
  86 }
  87
  88 static struct hwrng omap_rng_ops = {
  89         .name           = "omap",
  90         .data_present   = omap_rng_data_present,
  91         .data_read      = omap_rng_data_read,
  92 };
  93
  94 static int __devinit omap_rng_probe(struct platform_device *pdev)
  95 {
  96         struct resource *res;
  97         int ret;
  98
  99         /*
 100          * A bit ugly, and it will never actually happen but there can
 101          * be only one RNG and this catches any bork
 102          */
 103         if (rng_dev)
 104                 return -EBUSY;
 105
 106         if (cpu_is_omap24xx()) {
 107                 rng_ick = clk_get(&pdev->dev, "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         rng_base = devm_request_and_ioremap(&pdev->dev, res);
 119         if (!rng_base) {
 120                 ret = -ENOMEM;
 121                 goto err_ioremap;
 122         }
 123         dev_set_drvdata(&pdev->dev, res);
 124
 125         ret = hwrng_register(&omap_rng_ops);
 126         if (ret)
 127                 goto err_register;
 128
 129         dev_info(&pdev->dev, "OMAP Random Number Generator ver. %02x\n",
 130                 omap_rng_read_reg(RNG_REV_REG));
 131         omap_rng_write_reg(RNG_MASK_REG, 0x1);
 132
 133         rng_dev = pdev;
 134
 135         return 0;
 136
 137 err_register:
 138         rng_base = NULL;
 139 err_ioremap:
 140         if (cpu_is_omap24xx()) {
 141                 clk_disable(rng_ick);
 142                 clk_put(rng_ick);
 143         }
 144         return ret;
 145 }
 146
 147 static int __exit omap_rng_remove(struct platform_device *pdev)
 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         rng_base = NULL;
 159
 160         return 0;
 161 }
 162
 163 #ifdef CONFIG_PM
 164
 165 static int omap_rng_suspend(struct platform_device *pdev, pm_message_t message)
 166 {
 167         omap_rng_write_reg(RNG_MASK_REG, 0x0);
 168         return 0;
 169 }
 170
 171 static int omap_rng_resume(struct platform_device *pdev)
 172 {
 173         omap_rng_write_reg(RNG_MASK_REG, 0x1);
 174         return 0;
 175 }
 176
 177 #else
 178
 179 #define omap_rng_suspend        NULL
 180 #define omap_rng_resume         NULL
 181
 182 #endif
 183
 184 /* work with hotplug and coldplug */
 185 MODULE_ALIAS("platform:omap_rng");
 186
 187 static struct platform_driver omap_rng_driver = {
 188         .driver = {
 189                 .name           = "omap_rng",
 190                 .owner          = THIS_MODULE,
 191         },
 192         .probe          = omap_rng_probe,
 193         .remove         = __exit_p(omap_rng_remove),
 194         .suspend        = omap_rng_suspend,
 195         .resume         = omap_rng_resume
 196 };
 197
 198 static int __init omap_rng_init(void)
 199 {
 200         if (!cpu_is_omap16xx() && !cpu_is_omap24xx())
 201                 return -ENODEV;
 202
 203         return platform_driver_register(&omap_rng_driver);
 204 }
 205
 206 static void __exit omap_rng_exit(void)
 207 {
 208         platform_driver_unregister(&omap_rng_driver);
 209 }
 210
 211 module_init(omap_rng_init);
 212 module_exit(omap_rng_exit);
 213
 214 MODULE_AUTHOR("Deepak Saxena (and others)");
 215 MODULE_LICENSE("GPL");