drivers/char/omap-rng.c

   1 /*
   2  * drivers/char/omap-rng.c
   3  *
   4  * Copyright (C) 2005 Nokia Corporation
   5  * Author: Juha Yrjölä <juha.yrjola@nokia.com>
   6  *
   7  * OMAP16xx and OMAP24xx Random Number Generator driver
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License version 2 as
  11  * published by the Free Software Foundation.
  12  *
  13  */
  14
  15 #include <linux/module.h>
  16 #include <linux/init.h>
  17 #include <linux/random.h>
  18 #include <linux/err.h>
  19 #include <linux/clk.h>
  20
  21 #include <asm/io.h>
  22
  23 #if defined (CONFIG_ARCH_OMAP16XX)
  24 #define RNG_BASE                0xfffe5000
  25 #endif
  26 #if defined (CONFIG_ARCH_OMAP24XX)
  27 #define RNG_BASE                0x480A0000
  28 #endif
  29
  30 #define RNG_OUT_REG             0x00            /* Output register */
  31 #define RNG_STAT_REG            0x04            /* Status register
  32                                                         [0] = STAT_BUSY */
  33 #define RNG_ALARM_REG           0x24            /* Alarm register
  34                                                         [7:0] = ALARM_COUNTER */
  35 #define RNG_CONFIG_REG          0x28            /* Configuration register
  36                                                         [11:6] = RESET_COUNT
  37                                                         [5:3]  = RING2_DELAY
  38                                                         [2:0]  = RING1_DELAY */
  39 #define RNG_REV_REG             0x3c            /* Revision register
  40                                                         [7:0] = REV_NB */
  41 #define RNG_MASK_REG            0x40            /* Mask and reset register
  42                                                         [2] = IT_EN
  43                                                         [1] = SOFTRESET
  44                                                         [0] = AUTOIDLE */
  45 #define RNG_SYSSTATUS           0x44            /* System status
  46                                                         [0] = RESETDONE */
  47
  48 #define ENTROPY_WORD_COUNT      128
  49
  50 static u32 rng_base = io_p2v(RNG_BASE);
  51
  52 static struct clk *rng_ick = NULL;
  53
  54 static u32 rng_read_reg(int reg)
  55 {
  56         return __raw_readl(rng_base + reg);
  57 }
  58
  59 static void rng_write_reg(int reg, u32 val)
  60 {
  61         __raw_writel(val, rng_base + reg);
  62 }
  63
  64 static void rng_feed_entropy(int count)
  65 {
  66         u32 l;
  67
  68         while (count--) {
  69                 while (rng_read_reg(RNG_STAT_REG));
  70                 l = rng_read_reg(RNG_OUT_REG);
  71                 add_input_randomness(0, 0, l);
  72         }
  73 }
  74
  75 static int __init rng_init(void)
  76 {
  77         if (!cpu_is_omap16xx() && !cpu_is_omap24xx())
  78                 return -ENODEV;
  79
  80         if (cpu_is_omap24xx()) {
  81                 rng_ick = clk_get(NULL, "rng_ick");
  82                 if (IS_ERR(rng_ick)) {
  83                         printk(KERN_ERR "omap-rng.c: Could not get rng_ick\n");
  84                         return PTR_ERR(rng_ick);
  85                 }
  86                 clk_enable(rng_ick);
  87         }
  88
  89         printk("OMAP Random Number Generator ver. %02x\n",
  90         rng_read_reg(RNG_REV_REG));
  91         rng_write_reg(RNG_MASK_REG, 0x00000001);
  92         rng_feed_entropy(ENTROPY_WORD_COUNT);
  93         rng_write_reg(RNG_MASK_REG, 0x00000000);
  94         printk("%d words of entropy generated\n", ENTROPY_WORD_COUNT);
  95
  96         return 0;
  97 }
  98 late_initcall(rng_init);