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/of.h>
  24 #include <linux/of_device.h>
  25 #include <linux/platform_device.h>
  26
  27 #define RNG_RESET                       0x01
  28 #define RNG_GEN_PRNG_HW_INIT            0x02
  29 #define RNG_GEN_HW                      0x08
  30
  31 /* param1: ptr, param2: count, param3: flag */
  32 static u32 (*omap3_rom_rng_call)(u32, u32, u32);
  33
  34 static struct delayed_work idle_work;
  35 static int rng_idle;
  36 static struct clk *rng_clk;
  37
  38 static void omap3_rom_rng_idle(struct work_struct *work)
  39 {
  40         int r;
  41
  42         r = omap3_rom_rng_call(0, 0, RNG_RESET);
  43         if (r != 0) {
  44                 pr_err("reset failed: %d\n", r);
  45                 return;
  46         }
  47         clk_disable_unprepare(rng_clk);
  48         rng_idle = 1;
  49 }
  50
  51 static int omap3_rom_rng_get_random(void *buf, unsigned int count)
  52 {
  53         u32 r;
  54         u32 ptr;
  55
  56         cancel_delayed_work_sync(&idle_work);
  57         if (rng_idle) {
  58                 r = clk_prepare_enable(rng_clk);
  59                 if (r)
  60                         return r;
  61
  62                 r = omap3_rom_rng_call(0, 0, RNG_GEN_PRNG_HW_INIT);
  63                 if (r != 0) {
  64                         clk_disable_unprepare(rng_clk);
  65                         pr_err("HW init failed: %d\n", r);
  66                         return -EIO;
  67                 }
  68                 rng_idle = 0;
  69         }
  70
  71         ptr = virt_to_phys(buf);
  72         r = omap3_rom_rng_call(ptr, count, RNG_GEN_HW);
  73         schedule_delayed_work(&idle_work, msecs_to_jiffies(500));
  74         if (r != 0)
  75                 return -EINVAL;
  76         return 0;
  77 }
  78
  79 static int omap3_rom_rng_read(struct hwrng *rng, void *data, size_t max, bool w)
  80 {
  81         int r;
  82
  83         r = omap3_rom_rng_get_random(data, 4);
  84         if (r < 0)
  85                 return r;
  86         return 4;
  87 }
  88
  89 static struct hwrng omap3_rom_rng_ops = {
  90         .name           = "omap3-rom",
  91 };
  92
  93 static int omap3_rom_rng_probe(struct platform_device *pdev)
  94 {
  95         int ret = 0;
  96
  97         omap3_rom_rng_ops.read = of_device_get_match_data(&pdev->dev);
  98         if (!omap3_rom_rng_ops.read) {
  99                 dev_err(&pdev->dev, "missing rom code handler\n");
 100
 101                 return -ENODEV;
 102         }
 103
 104         omap3_rom_rng_call = pdev->dev.platform_data;
 105         if (!omap3_rom_rng_call) {
 106                 pr_err("omap3_rom_rng_call is NULL\n");
 107                 return -EINVAL;
 108         }
 109
 110         INIT_DELAYED_WORK(&idle_work, omap3_rom_rng_idle);
 111         rng_clk = devm_clk_get(&pdev->dev, "ick");
 112         if (IS_ERR(rng_clk)) {
 113                 pr_err("unable to get RNG clock\n");
 114                 return PTR_ERR(rng_clk);
 115         }
 116
 117         /* Leave the RNG in reset state. */
 118         ret = clk_prepare_enable(rng_clk);
 119         if (ret)
 120                 return ret;
 121         omap3_rom_rng_idle(0);
 122
 123         return hwrng_register(&omap3_rom_rng_ops);
 124 }
 125
 126 static int omap3_rom_rng_remove(struct platform_device *pdev)
 127 {
 128         cancel_delayed_work_sync(&idle_work);
 129         hwrng_unregister(&omap3_rom_rng_ops);
 130         if (!rng_idle)
 131                 clk_disable_unprepare(rng_clk);
 132         return 0;
 133 }
 134
 135 static const struct of_device_id omap_rom_rng_match[] = {
 136         { .compatible = "nokia,n900-rom-rng", .data = omap3_rom_rng_read, },
 137         { /* sentinel */ },
 138 };
 139 MODULE_DEVICE_TABLE(of, omap_rom_rng_match);
 140
 141 static struct platform_driver omap3_rom_rng_driver = {
 142         .driver = {
 143                 .name           = "omap3-rom-rng",
 144                 .of_match_table = omap_rom_rng_match,
 145         },
 146         .probe          = omap3_rom_rng_probe,
 147         .remove         = omap3_rom_rng_remove,
 148 };
 149
 150 module_platform_driver(omap3_rom_rng_driver);
 151
 152 MODULE_ALIAS("platform:omap3-rom-rng");
 153 MODULE_AUTHOR("Juha Yrjola");
 154 MODULE_AUTHOR("Pali Rohár <pali.rohar@gmail.com>");
 155 MODULE_LICENSE("GPL");