LXR linux/drivers/char/hw_random/atmel-rng.c

   1/*
   2 * Copyright (c) 2011 Peter Korsgaard <jacmet@sunsite.dk>
   3 *
   4 * This file is licensed under  the terms of the GNU General Public
   5 * License version 2. This program is licensed "as is" without any
   6 * warranty of any kind, whether express or implied.
   7 */
   8
   9#include <linux/kernel.h>
  10#include <linux/module.h>
  11#include <linux/mod_devicetable.h>
  12#include <linux/slab.h>
  13#include <linux/err.h>
  14#include <linux/clk.h>
  15#include <linux/io.h>
  16#include <linux/hw_random.h>
  17#include <linux/of_device.h>
  18#include <linux/platform_device.h>
  19
  20#define TRNG_CR         0x00
  21#define TRNG_MR         0x04
  22#define TRNG_ISR        0x1c
  23#define TRNG_ODATA      0x50
  24
  25#define TRNG_KEY        0x524e4700 /* RNG */
  26
  27#define TRNG_HALFR      BIT(0) /* generate RN every 168 cycles */
  28
  29struct atmel_trng_data {
  30        bool has_half_rate;
  31};
  32
  33struct atmel_trng {
  34        struct clk *clk;
  35        void __iomem *base;
  36        struct hwrng rng;
  37};
  38
  39static int atmel_trng_read(struct hwrng *rng, void *buf, size_t max,
  40                           bool wait)
  41{
  42        struct atmel_trng *trng = container_of(rng, struct atmel_trng, rng);
  43        u32 *data = buf;
  44
  45        /* data ready? */
  46        if (readl(trng->base + TRNG_ISR) & 1) {
  47                *data = readl(trng->base + TRNG_ODATA);
  48                /*
  49                  ensure data ready is only set again AFTER the next data
  50                  word is ready in case it got set between checking ISR
  51                  and reading ODATA, so we don't risk re-reading the
  52                  same word
  53                */
  54                readl(trng->base + TRNG_ISR);
  55                return 4;
  56        } else
  57                return 0;
  58}
  59
  60static void atmel_trng_enable(struct atmel_trng *trng)
  61{
  62        writel(TRNG_KEY | 1, trng->base + TRNG_CR);
  63}
  64
  65static void atmel_trng_disable(struct atmel_trng *trng)
  66{
  67        writel(TRNG_KEY, trng->base + TRNG_CR);
  68}
  69
  70static int atmel_trng_probe(struct platform_device *pdev)
  71{
  72        struct atmel_trng *trng;
  73        const struct atmel_trng_data *data;
  74        int ret;
  75
  76        trng = devm_kzalloc(&pdev->dev, sizeof(*trng), GFP_KERNEL);
  77        if (!trng)
  78                return -ENOMEM;
  79
  80        trng->base = devm_platform_ioremap_resource(pdev, 0);
  81        if (IS_ERR(trng->base))
  82                return PTR_ERR(trng->base);
  83
  84        trng->clk = devm_clk_get(&pdev->dev, NULL);
  85        if (IS_ERR(trng->clk))
  86                return PTR_ERR(trng->clk);
  87        data = of_device_get_match_data(&pdev->dev);
  88        if (!data)
  89                return -ENODEV;
  90
  91        if (data->has_half_rate) {
  92                unsigned long rate = clk_get_rate(trng->clk);
  93
  94                /* if peripheral clk is above 100MHz, set HALFR */
  95                if (rate > 100000000)
  96                        writel(TRNG_HALFR, trng->base + TRNG_MR);
  97        }
  98
  99        ret = clk_prepare_enable(trng->clk);
 100        if (ret)
 101                return ret;
 102
 103        atmel_trng_enable(trng);
 104        trng->rng.name = pdev->name;
 105        trng->rng.read = atmel_trng_read;
 106
 107        ret = devm_hwrng_register(&pdev->dev, &trng->rng);
 108        if (ret)
 109                goto err_register;
 110
 111        platform_set_drvdata(pdev, trng);
 112
 113        return 0;
 114
 115err_register:
 116        clk_disable_unprepare(trng->clk);
 117        return ret;
 118}
 119
 120static int atmel_trng_remove(struct platform_device *pdev)
 121{
 122        struct atmel_trng *trng = platform_get_drvdata(pdev);
 123
 124
 125        atmel_trng_disable(trng);
 126        clk_disable_unprepare(trng->clk);
 127
 128        return 0;
 129}
 130
 131#ifdef CONFIG_PM
 132static int atmel_trng_suspend(struct device *dev)
 133{
 134        struct atmel_trng *trng = dev_get_drvdata(dev);
 135
 136        atmel_trng_disable(trng);
 137        clk_disable_unprepare(trng->clk);
 138
 139        return 0;
 140}
 141
 142static int atmel_trng_resume(struct device *dev)
 143{
 144        struct atmel_trng *trng = dev_get_drvdata(dev);
 145        int ret;
 146
 147        ret = clk_prepare_enable(trng->clk);
 148        if (ret)
 149                return ret;
 150
 151        atmel_trng_enable(trng);
 152
 153        return 0;
 154}
 155
 156static const struct dev_pm_ops atmel_trng_pm_ops = {
 157        .suspend        = atmel_trng_suspend,
 158        .resume         = atmel_trng_resume,
 159};
 160#endif /* CONFIG_PM */
 161
 162static const struct atmel_trng_data at91sam9g45_config = {
 163        .has_half_rate = false,
 164};
 165
 166static const struct atmel_trng_data sam9x60_config = {
 167        .has_half_rate = true,
 168};
 169
 170static const struct of_device_id atmel_trng_dt_ids[] = {
 171        {
 172                .compatible = "atmel,at91sam9g45-trng",
 173                .data = &at91sam9g45_config,
 174        }, {
 175                .compatible = "microchip,sam9x60-trng",
 176                .data = &sam9x60_config,
 177        }, {
 178                /* sentinel */
 179        }
 180};
 181MODULE_DEVICE_TABLE(of, atmel_trng_dt_ids);
 182
 183static struct platform_driver atmel_trng_driver = {
 184        .probe          = atmel_trng_probe,
 185        .remove         = atmel_trng_remove,
 186        .driver         = {
 187                .name   = "atmel-trng",
 188#ifdef CONFIG_PM
 189                .pm     = &atmel_trng_pm_ops,
 190#endif /* CONFIG_PM */
 191                .of_match_table = atmel_trng_dt_ids,
 192        },
 193};
 194
 195module_platform_driver(atmel_trng_driver);
 196
 197MODULE_LICENSE("GPL");
 198MODULE_AUTHOR("Peter Korsgaard <jacmet@sunsite.dk>");
 199MODULE_DESCRIPTION("Atmel true random number generator driver");
 200