Loading...
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 | // SPDX-License-Identifier: GPL-2.0-only
/*
* ST Random Number Generator Driver ST's Platforms
*
* Author: Pankaj Dev: <pankaj.dev@st.com>
* Lee Jones <lee.jones@linaro.org>
*
* Copyright (C) 2015 STMicroelectronics (R&D) Limited
*/
#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/hw_random.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
/* Registers */
#define ST_RNG_STATUS_REG 0x20
#define ST_RNG_DATA_REG 0x24
/* Registers fields */
#define ST_RNG_STATUS_BAD_SEQUENCE BIT(0)
#define ST_RNG_STATUS_BAD_ALTERNANCE BIT(1)
#define ST_RNG_STATUS_FIFO_FULL BIT(5)
#define ST_RNG_SAMPLE_SIZE 2 /* 2 Byte (16bit) samples */
#define ST_RNG_FIFO_DEPTH 4
#define ST_RNG_FIFO_SIZE (ST_RNG_FIFO_DEPTH * ST_RNG_SAMPLE_SIZE)
/*
* Samples are documented to be available every 0.667us, so in theory
* the 4 sample deep FIFO should take 2.668us to fill. However, during
* thorough testing, it became apparent that filling the FIFO actually
* takes closer to 12us. We then multiply by 2 in order to account for
* the lack of udelay()'s reliability, suggested by Russell King.
*/
#define ST_RNG_FILL_FIFO_TIMEOUT (12 * 2)
struct st_rng_data {
void __iomem *base;
struct clk *clk;
struct hwrng ops;
};
static int st_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
{
struct st_rng_data *ddata = (struct st_rng_data *)rng->priv;
u32 status;
int i;
/* Wait until FIFO is full - max 4uS*/
for (i = 0; i < ST_RNG_FILL_FIFO_TIMEOUT; i++) {
status = readl_relaxed(ddata->base + ST_RNG_STATUS_REG);
if (status & ST_RNG_STATUS_FIFO_FULL)
break;
udelay(1);
}
if (i == ST_RNG_FILL_FIFO_TIMEOUT)
return 0;
for (i = 0; i < ST_RNG_FIFO_SIZE && i < max; i += 2)
*(u16 *)(data + i) =
readl_relaxed(ddata->base + ST_RNG_DATA_REG);
return i; /* No of bytes read */
}
static int st_rng_probe(struct platform_device *pdev)
{
struct st_rng_data *ddata;
struct clk *clk;
void __iomem *base;
int ret;
ddata = devm_kzalloc(&pdev->dev, sizeof(*ddata), GFP_KERNEL);
if (!ddata)
return -ENOMEM;
base = devm_platform_ioremap_resource(pdev, 0);
if (IS_ERR(base))
return PTR_ERR(base);
clk = devm_clk_get(&pdev->dev, NULL);
if (IS_ERR(clk))
return PTR_ERR(clk);
ret = clk_prepare_enable(clk);
if (ret)
return ret;
ddata->ops.priv = (unsigned long)ddata;
ddata->ops.read = st_rng_read;
ddata->ops.name = pdev->name;
ddata->base = base;
ddata->clk = clk;
dev_set_drvdata(&pdev->dev, ddata);
ret = devm_hwrng_register(&pdev->dev, &ddata->ops);
if (ret) {
dev_err(&pdev->dev, "Failed to register HW RNG\n");
clk_disable_unprepare(clk);
return ret;
}
dev_info(&pdev->dev, "Successfully registered HW RNG\n");
return 0;
}
static int st_rng_remove(struct platform_device *pdev)
{
struct st_rng_data *ddata = dev_get_drvdata(&pdev->dev);
clk_disable_unprepare(ddata->clk);
return 0;
}
static const struct of_device_id st_rng_match[] = {
{ .compatible = "st,rng" },
{},
};
MODULE_DEVICE_TABLE(of, st_rng_match);
static struct platform_driver st_rng_driver = {
.driver = {
.name = "st-hwrandom",
.of_match_table = of_match_ptr(st_rng_match),
},
.probe = st_rng_probe,
.remove = st_rng_remove
};
module_platform_driver(st_rng_driver);
MODULE_AUTHOR("Pankaj Dev <pankaj.dev@st.com>");
MODULE_LICENSE("GPL v2");
|