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// SPDX-License-Identifier: GPL-2.0
// Copyright (c) 2020 Silex Insight
#include <linux/delay.h>
#include <linux/hw_random.h>
#include <linux/io.h>
#include <linux/iopoll.h>
#include <linux/kernel.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/workqueue.h>
#define BA431_RESET_DELAY 1 /* usec */
#define BA431_RESET_READ_STATUS_TIMEOUT 1000 /* usec */
#define BA431_RESET_READ_STATUS_INTERVAL 10 /* usec */
#define BA431_READ_RETRY_INTERVAL 1 /* usec */
#define BA431_REG_CTRL 0x00
#define BA431_REG_FIFO_LEVEL 0x04
#define BA431_REG_STATUS 0x30
#define BA431_REG_FIFODATA 0x80
#define BA431_CTRL_ENABLE BIT(0)
#define BA431_CTRL_SOFTRESET BIT(8)
#define BA431_STATUS_STATE_MASK (BIT(1) | BIT(2) | BIT(3))
#define BA431_STATUS_STATE_OFFSET 1
enum ba431_state {
BA431_STATE_RESET,
BA431_STATE_STARTUP,
BA431_STATE_FIFOFULLON,
BA431_STATE_FIFOFULLOFF,
BA431_STATE_RUNNING,
BA431_STATE_ERROR
};
struct ba431_trng {
struct device *dev;
void __iomem *base;
struct hwrng rng;
atomic_t reset_pending;
struct work_struct reset_work;
};
static inline u32 ba431_trng_read_reg(struct ba431_trng *ba431, u32 reg)
{
return ioread32(ba431->base + reg);
}
static inline void ba431_trng_write_reg(struct ba431_trng *ba431, u32 reg,
u32 val)
{
iowrite32(val, ba431->base + reg);
}
static inline enum ba431_state ba431_trng_get_state(struct ba431_trng *ba431)
{
u32 status = ba431_trng_read_reg(ba431, BA431_REG_STATUS);
return (status & BA431_STATUS_STATE_MASK) >> BA431_STATUS_STATE_OFFSET;
}
static int ba431_trng_is_in_error(struct ba431_trng *ba431)
{
enum ba431_state state = ba431_trng_get_state(ba431);
if ((state < BA431_STATE_STARTUP) ||
(state >= BA431_STATE_ERROR))
return 1;
return 0;
}
static int ba431_trng_reset(struct ba431_trng *ba431)
{
int ret;
/* Disable interrupts, random generation and enable the softreset */
ba431_trng_write_reg(ba431, BA431_REG_CTRL, BA431_CTRL_SOFTRESET);
udelay(BA431_RESET_DELAY);
ba431_trng_write_reg(ba431, BA431_REG_CTRL, BA431_CTRL_ENABLE);
/* Wait until the state changed */
if (readx_poll_timeout(ba431_trng_is_in_error, ba431, ret, !ret,
BA431_RESET_READ_STATUS_INTERVAL,
BA431_RESET_READ_STATUS_TIMEOUT)) {
dev_err(ba431->dev, "reset failed (state: %d)\n",
ba431_trng_get_state(ba431));
return -ETIMEDOUT;
}
dev_info(ba431->dev, "reset done\n");
return 0;
}
static void ba431_trng_reset_work(struct work_struct *work)
{
struct ba431_trng *ba431 = container_of(work, struct ba431_trng,
reset_work);
ba431_trng_reset(ba431);
atomic_set(&ba431->reset_pending, 0);
}
static void ba431_trng_schedule_reset(struct ba431_trng *ba431)
{
if (atomic_cmpxchg(&ba431->reset_pending, 0, 1))
return;
schedule_work(&ba431->reset_work);
}
static int ba431_trng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
{
struct ba431_trng *ba431 = container_of(rng, struct ba431_trng, rng);
u32 *data = buf;
unsigned int level, i;
int n = 0;
while (max > 0) {
level = ba431_trng_read_reg(ba431, BA431_REG_FIFO_LEVEL);
if (!level) {
if (ba431_trng_is_in_error(ba431)) {
ba431_trng_schedule_reset(ba431);
break;
}
if (!wait)
break;
udelay(BA431_READ_RETRY_INTERVAL);
continue;
}
i = level;
do {
data[n++] = ba431_trng_read_reg(ba431,
BA431_REG_FIFODATA);
max -= sizeof(*data);
} while (--i && (max > 0));
if (ba431_trng_is_in_error(ba431)) {
n -= (level - i);
ba431_trng_schedule_reset(ba431);
break;
}
}
n *= sizeof(data);
return (n || !wait) ? n : -EIO;
}
static void ba431_trng_cleanup(struct hwrng *rng)
{
struct ba431_trng *ba431 = container_of(rng, struct ba431_trng, rng);
ba431_trng_write_reg(ba431, BA431_REG_CTRL, 0);
cancel_work_sync(&ba431->reset_work);
}
static int ba431_trng_init(struct hwrng *rng)
{
struct ba431_trng *ba431 = container_of(rng, struct ba431_trng, rng);
return ba431_trng_reset(ba431);
}
static int ba431_trng_probe(struct platform_device *pdev)
{
struct ba431_trng *ba431;
struct resource *res;
int ret;
ba431 = devm_kzalloc(&pdev->dev, sizeof(*ba431), GFP_KERNEL);
if (!ba431)
return -ENOMEM;
ba431->dev = &pdev->dev;
res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
ba431->base = devm_ioremap_resource(&pdev->dev, res);
if (IS_ERR(ba431->base))
return PTR_ERR(ba431->base);
atomic_set(&ba431->reset_pending, 0);
INIT_WORK(&ba431->reset_work, ba431_trng_reset_work);
ba431->rng.name = pdev->name;
ba431->rng.init = ba431_trng_init;
ba431->rng.cleanup = ba431_trng_cleanup;
ba431->rng.read = ba431_trng_read;
platform_set_drvdata(pdev, ba431);
ret = hwrng_register(&ba431->rng);
if (ret) {
dev_err(&pdev->dev, "BA431 registration failed (%d)\n", ret);
return ret;
}
dev_info(&pdev->dev, "BA431 TRNG registered\n");
return 0;
}
static int ba431_trng_remove(struct platform_device *pdev)
{
struct ba431_trng *ba431 = platform_get_drvdata(pdev);
hwrng_unregister(&ba431->rng);
return 0;
}
static const struct of_device_id ba431_trng_dt_ids[] = {
{ .compatible = "silex-insight,ba431-rng", .data = NULL },
{ /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, ba431_trng_dt_ids);
static struct platform_driver ba431_trng_driver = {
.driver = {
.name = "ba431-rng",
.of_match_table = ba431_trng_dt_ids,
},
.probe = ba431_trng_probe,
.remove = ba431_trng_remove,
};
module_platform_driver(ba431_trng_driver);
MODULE_AUTHOR("Olivier Sobrie <olivier@sobrie.be>");
MODULE_DESCRIPTION("TRNG driver for Silex Insight BA431");
MODULE_LICENSE("GPL");
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