tx4939-rng.c
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/*
* RNG driver for TX4939 Random Number Generators (RNG)
*
* Copyright (C) 2009 Atsushi Nemoto <anemo@mba.ocn.ne.jp>
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*/
#include <linux/err.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/io.h>
#include <linux/platform_device.h>
#include <linux/hw_random.h>
#include <linux/gfp.h>
#define TX4939_RNG_RCSR 0x00000000
#define TX4939_RNG_ROR(n) (0x00000018 + (n) * 8)
#define TX4939_RNG_RCSR_INTE 0x00000008
#define TX4939_RNG_RCSR_RST 0x00000004
#define TX4939_RNG_RCSR_FIN 0x00000002
#define TX4939_RNG_RCSR_ST 0x00000001
struct tx4939_rng {
struct hwrng rng;
void __iomem *base;
u64 databuf[3];
unsigned int data_avail;
};
static void rng_io_start(void)
{
#ifndef CONFIG_64BIT
/*
* readq is reading a 64-bit register using a 64-bit load. On
* a 32-bit kernel however interrupts or any other processor
* exception would clobber the upper 32-bit of the processor
* register so interrupts need to be disabled.
*/
local_irq_disable();
#endif
}
static void rng_io_end(void)
{
#ifndef CONFIG_64BIT
local_irq_enable();
#endif
}
static u64 read_rng(void __iomem *base, unsigned int offset)
{
return ____raw_readq(base + offset);
}
static void write_rng(u64 val, void __iomem *base, unsigned int offset)
{
return ____raw_writeq(val, base + offset);
}
static int tx4939_rng_data_present(struct hwrng *rng, int wait)
{
struct tx4939_rng *rngdev = container_of(rng, struct tx4939_rng, rng);
int i;
if (rngdev->data_avail)
return rngdev->data_avail;
for (i = 0; i < 20; i++) {
rng_io_start();
if (!(read_rng(rngdev->base, TX4939_RNG_RCSR)
& TX4939_RNG_RCSR_ST)) {
rngdev->databuf[0] =
read_rng(rngdev->base, TX4939_RNG_ROR(0));
rngdev->databuf[1] =
read_rng(rngdev->base, TX4939_RNG_ROR(1));
rngdev->databuf[2] =
read_rng(rngdev->base, TX4939_RNG_ROR(2));
rngdev->data_avail =
sizeof(rngdev->databuf) / sizeof(u32);
/* Start RNG */
write_rng(TX4939_RNG_RCSR_ST,
rngdev->base, TX4939_RNG_RCSR);
wait = 0;
}
rng_io_end();
if (!wait)
break;
/* 90 bus clock cycles by default for generation */
ndelay(90 * 5);
}
return rngdev->data_avail;
}
static int tx4939_rng_data_read(struct hwrng *rng, u32 *buffer)
{
struct tx4939_rng *rngdev = container_of(rng, struct tx4939_rng, rng);
rngdev->data_avail--;
*buffer = *((u32 *)&rngdev->databuf + rngdev->data_avail);
return sizeof(u32);
}
static int __init tx4939_rng_probe(struct platform_device *dev)
{
struct tx4939_rng *rngdev;
struct resource *r;
int i;
rngdev = devm_kzalloc(&dev->dev, sizeof(*rngdev), GFP_KERNEL);
if (!rngdev)
return -ENOMEM;
r = platform_get_resource(dev, IORESOURCE_MEM, 0);
rngdev->base = devm_ioremap_resource(&dev->dev, r);
if (IS_ERR(rngdev->base))
return PTR_ERR(rngdev->base);
rngdev->rng.name = dev_name(&dev->dev);
rngdev->rng.data_present = tx4939_rng_data_present;
rngdev->rng.data_read = tx4939_rng_data_read;
rng_io_start();
/* Reset RNG */
write_rng(TX4939_RNG_RCSR_RST, rngdev->base, TX4939_RNG_RCSR);
write_rng(0, rngdev->base, TX4939_RNG_RCSR);
/* Start RNG */
write_rng(TX4939_RNG_RCSR_ST, rngdev->base, TX4939_RNG_RCSR);
rng_io_end();
/*
* Drop first two results. From the datasheet:
* The quality of the random numbers generated immediately
* after reset can be insufficient. Therefore, do not use
* random numbers obtained from the first and second
* generations; use the ones from the third or subsequent
* generation.
*/
for (i = 0; i < 2; i++) {
rngdev->data_avail = 0;
if (!tx4939_rng_data_present(&rngdev->rng, 1))
return -EIO;
}
platform_set_drvdata(dev, rngdev);
return hwrng_register(&rngdev->rng);
}
static int __exit tx4939_rng_remove(struct platform_device *dev)
{
struct tx4939_rng *rngdev = platform_get_drvdata(dev);
hwrng_unregister(&rngdev->rng);
return 0;
}
static struct platform_driver tx4939_rng_driver = {
.driver = {
.name = "tx4939-rng",
},
.remove = tx4939_rng_remove,
};
module_platform_driver_probe(tx4939_rng_driver, tx4939_rng_probe);
MODULE_DESCRIPTION("H/W Random Number Generator (RNG) driver for TX4939");
MODULE_LICENSE("GPL");