LXR linux/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 */
  30static u32 (*omap3_rom_rng_call)(u32, u32, u32);
  31
  32static struct delayed_work idle_work;
  33static int rng_idle;
  34static struct clk *rng_clk;
  35
  36static 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
  49static 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                r = clk_prepare_enable(rng_clk);
  57                if (r)
  58                        return r;
  59
  60                r = omap3_rom_rng_call(0, 0, RNG_GEN_PRNG_HW_INIT);
  61                if (r != 0) {
  62                        clk_disable_unprepare(rng_clk);
  63                        pr_err("HW init failed: %d\n", r);
  64                        return -EIO;
  65                }
  66                rng_idle = 0;
  67        }
  68
  69        ptr = virt_to_phys(buf);
  70        r = omap3_rom_rng_call(ptr, count, RNG_GEN_HW);
  71        schedule_delayed_work(&idle_work, msecs_to_jiffies(500));
  72        if (r != 0)
  73                return -EINVAL;
  74        return 0;
  75}
  76
  77static int omap3_rom_rng_read(struct hwrng *rng, void *data, size_t max, bool w)
  78{
  79        int r;
  80
  81        r = omap3_rom_rng_get_random(data, 4);
  82        if (r < 0)
  83                return r;
  84        return 4;
  85}
  86
  87static struct hwrng omap3_rom_rng_ops = {
  88        .name           = "omap3-rom",
  89        .read           = omap3_rom_rng_read,
  90};
  91
  92static int omap3_rom_rng_probe(struct platform_device *pdev)
  93{
  94        int ret = 0;
  95
  96        pr_info("initializing\n");
  97
  98        omap3_rom_rng_call = pdev->dev.platform_data;
  99        if (!omap3_rom_rng_call) {
 100                pr_err("omap3_rom_rng_call is NULL\n");
 101                return -EINVAL;
 102        }
 103
 104        INIT_DELAYED_WORK(&idle_work, omap3_rom_rng_idle);
 105        rng_clk = devm_clk_get(&pdev->dev, "ick");
 106        if (IS_ERR(rng_clk)) {
 107                pr_err("unable to get RNG clock\n");
 108                return PTR_ERR(rng_clk);
 109        }
 110
 111        /* Leave the RNG in reset state. */
 112        ret = clk_prepare_enable(rng_clk);
 113        if (ret)
 114                return ret;
 115        omap3_rom_rng_idle(0);
 116
 117        return hwrng_register(&omap3_rom_rng_ops);
 118}
 119
 120static int omap3_rom_rng_remove(struct platform_device *pdev)
 121{
 122        cancel_delayed_work_sync(&idle_work);
 123        hwrng_unregister(&omap3_rom_rng_ops);
 124        clk_disable_unprepare(rng_clk);
 125        return 0;
 126}
 127
 128static struct platform_driver omap3_rom_rng_driver = {
 129        .driver = {
 130                .name           = "omap3-rom-rng",
 131        },
 132        .probe          = omap3_rom_rng_probe,
 133        .remove         = omap3_rom_rng_remove,
 134};
 135
 136module_platform_driver(omap3_rom_rng_driver);
 137
 138MODULE_ALIAS("platform:omap3-rom-rng");
 139MODULE_AUTHOR("Juha Yrjola");
 140MODULE_AUTHOR("Pali Rohár <pali.rohar@gmail.com>");
 141MODULE_LICENSE("GPL");
 142