diff options
Diffstat (limited to 'drivers/char/hw_random/ba431-rng.c')
| -rw-r--r-- | drivers/char/hw_random/ba431-rng.c | 235 |
1 files changed, 235 insertions, 0 deletions
diff --git a/drivers/char/hw_random/ba431-rng.c b/drivers/char/hw_random/ba431-rng.c new file mode 100644 index 000000000000..410b50b05e21 --- /dev/null +++ b/drivers/char/hw_random/ba431-rng.c @@ -0,0 +1,235 @@ +// 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"); |