drivers/char/hw_random/omap3-rom-rng.c

   1 /*
   2  * omap3-rom-rng.c - RNG driver for TI OMAP3 CPU family
   3  *
   4  * Copyright (C) 2009 Nokia Corporation
   5  * Author: Juha Yrjola <juha.yrjola@solidboot.com>
   6  *
   7  * Copyright (C) 2013 Pali Rohár <pali.rohar@gmail.com>
   8  *
   9  * This file is licensed under  the terms of the GNU General Public
  10  * License version 2. This program is licensed "as is" without any
  11  * warranty of any kind, whether express or implied.
  12  */
  13
  14 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  15
  16 #include <linux/module.h>
  17 #include <linux/init.h>
  18 #include <linux/random.h>
  19 #include <linux/hw_random.h>
  20 #include <linux/workqueue.h>
  21 #include <linux/clk.h>
  22 #include <linux/err.h>
  23 #include <linux/platform_device.h>
  24
  25 #define RNG_RESET                       0x01
  26 #define RNG_GEN_PRNG_HW_INIT            0x02
  27 #define RNG_GEN_HW                      0x08
  28
  29 /* param1: ptr, param2: count, param3: flag */
  30 static u32 (*omap3_rom_rng_call)(u32, u32, u32);
  31
  32 static struct delayed_work idle_work;
  33 static int rng_idle;
  34 static struct clk *rng_clk;
  35
  36 static void omap3_rom_rng_idle(struct work_struct *work)
  37 {
  38         int r;
  39
  40         r = omap3_rom_rng_call(0, 0, RNG_RESET);
  41         if (r != 0) {
  42                 pr_err("reset failed: %d\n", r);
  43                 return;
  44         }
  45         clk_disable_unprepare(rng_clk);
  46         rng_idle = 1;
  47 }
  48
  49 static int omap3_rom_rng_get_random(void *buf, unsigned int count)
  50 {
  51         u32 r;
  52         u32 ptr;
  53
  54         cancel_delayed_work_sync(&idle_work);
  55         if (rng_idle) {
  56                 clk_prepare_enable(rng_clk);
  57                 r = omap3_rom_rng_call(0, 0, RNG_GEN_PRNG_HW_INIT);
  58                 if (r != 0) {
  59                         clk_disable_unprepare(rng_clk);
  60                         pr_err("HW init failed: %d\n", r);
  61                         return -EIO;
  62                 }
  63                 rng_idle = 0;
  64         }
  65
  66         ptr = virt_to_phys(buf);
  67         r = omap3_rom_rng_call(ptr, count, RNG_GEN_HW);
  68         schedule_delayed_work(&idle_work, msecs_to_jiffies(500));
  69         if (r != 0)
  70                 return -EINVAL;
  71         return 0;
  72 }
  73
  74 static int omap3_rom_rng_read(struct hwrng *rng, void *data, size_t max, bool w)
  75 {
  76         int r;
  77
  78         r = omap3_rom_rng_get_random(data, 4);
  79         if (r < 0)
  80                 return r;
  81         return 4;
  82 }
  83
  84 static struct hwrng omap3_rom_rng_ops = {
  85         .name           = "omap3-rom",
  86         .read           = omap3_rom_rng_read,
  87 };
  88
  89 static int omap3_rom_rng_probe(struct platform_device *pdev)
  90 {
  91         pr_info("initializing\n");
  92
  93         omap3_rom_rng_call = pdev->dev.platform_data;
  94         if (!omap3_rom_rng_call) {
  95                 pr_err("omap3_rom_rng_call is NULL\n");
  96                 return -EINVAL;
  97         }
  98
  99         INIT_DELAYED_WORK(&idle_work, omap3_rom_rng_idle);
 100         rng_clk = devm_clk_get(&pdev->dev, "ick");
 101         if (IS_ERR(rng_clk)) {
 102                 pr_err("unable to get RNG clock\n");
 103                 return PTR_ERR(rng_clk);
 104         }
 105
 106         /* Leave the RNG in reset state. */
 107         clk_prepare_enable(rng_clk);
 108         omap3_rom_rng_idle(0);
 109
 110         return hwrng_register(&omap3_rom_rng_ops);
 111 }
 112
 113 static int omap3_rom_rng_remove(struct platform_device *pdev)
 114 {
 115         cancel_delayed_work_sync(&idle_work);
 116         hwrng_unregister(&omap3_rom_rng_ops);
 117         clk_disable_unprepare(rng_clk);
 118         return 0;
 119 }
 120
 121 static struct platform_driver omap3_rom_rng_driver = {
 122         .driver = {
 123                 .name           = "omap3-rom-rng",
 124         },
 125         .probe          = omap3_rom_rng_probe,
 126         .remove         = omap3_rom_rng_remove,
 127 };
 128
 129 module_platform_driver(omap3_rom_rng_driver);
 130
 131 MODULE_ALIAS("platform:omap3-rom-rng");
 132 MODULE_AUTHOR("Juha Yrjola");
 133 MODULE_AUTHOR("Pali Rohár <pali.rohar@gmail.com>");
 134 MODULE_LICENSE("GPL");