145 lines
3.4 KiB
C
145 lines
3.4 KiB
C
// 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 resource *res;
|
|
struct clk *clk;
|
|
void __iomem *base;
|
|
int ret;
|
|
|
|
ddata = devm_kzalloc(&pdev->dev, sizeof(*ddata), GFP_KERNEL);
|
|
if (!ddata)
|
|
return -ENOMEM;
|
|
|
|
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
|
|
base = devm_ioremap_resource(&pdev->dev, res);
|
|
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");
|