linux/drivers/char/hw_random/st-rng.c
Thomas Gleixner d2912cb15b treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500
Based on 2 normalized pattern(s):

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license version 2 as
  published by the free software foundation

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license version 2 as
  published by the free software foundation #

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-only

has been chosen to replace the boilerplate/reference in 4122 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Enrico Weigelt <info@metux.net>
Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190604081206.933168790@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-06-19 17:09:55 +02:00

147 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 = hwrng_register(&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);
hwrng_unregister(&ddata->ops);
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");