diff options
Diffstat (limited to 'drivers/char/hw_random/xiphera-trng.c')
| -rw-r--r-- | drivers/char/hw_random/xiphera-trng.c | 150 |
1 files changed, 150 insertions, 0 deletions
diff --git a/drivers/char/hw_random/xiphera-trng.c b/drivers/char/hw_random/xiphera-trng.c new file mode 100644 index 000000000000..7bdab8c8a6a8 --- /dev/null +++ b/drivers/char/hw_random/xiphera-trng.c @@ -0,0 +1,150 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (C) 2020 Xiphera Ltd. */ + +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/mod_devicetable.h> +#include <linux/err.h> +#include <linux/io.h> +#include <linux/hw_random.h> +#include <linux/of_device.h> +#include <linux/platform_device.h> +#include <linux/delay.h> + +#define CONTROL_REG 0x00000000 +#define STATUS_REG 0x00000004 +#define RAND_REG 0x00000000 + +#define HOST_TO_TRNG_RESET 0x00000001 +#define HOST_TO_TRNG_RELEASE_RESET 0x00000002 +#define HOST_TO_TRNG_ENABLE 0x80000000 +#define HOST_TO_TRNG_ZEROIZE 0x80000004 +#define HOST_TO_TRNG_ACK_ZEROIZE 0x80000008 +#define HOST_TO_TRNG_READ 0x8000000F + +/* trng statuses */ +#define TRNG_ACK_RESET 0x000000AC +#define TRNG_SUCCESSFUL_STARTUP 0x00000057 +#define TRNG_FAILED_STARTUP 0x000000FA +#define TRNG_NEW_RAND_AVAILABLE 0x000000ED + +struct xiphera_trng { + void __iomem *mem; + struct hwrng rng; +}; + +static int xiphera_trng_read(struct hwrng *rng, void *buf, size_t max, bool wait) +{ + struct xiphera_trng *trng = container_of(rng, struct xiphera_trng, rng); + int ret = 0; + + while (max >= sizeof(u32)) { + /* check for data */ + if (readl(trng->mem + STATUS_REG) == TRNG_NEW_RAND_AVAILABLE) { + *(u32 *)buf = readl(trng->mem + RAND_REG); + /* + * Inform the trng of the read + * and re-enable it to produce a new random number + */ + writel(HOST_TO_TRNG_READ, trng->mem + CONTROL_REG); + writel(HOST_TO_TRNG_ENABLE, trng->mem + CONTROL_REG); + ret += sizeof(u32); + buf += sizeof(u32); + max -= sizeof(u32); + } else { + break; + } + } + return ret; +} + +static int xiphera_trng_probe(struct platform_device *pdev) +{ + int ret; + struct xiphera_trng *trng; + struct device *dev = &pdev->dev; + struct resource *res; + + trng = devm_kzalloc(dev, sizeof(*trng), GFP_KERNEL); + if (!trng) + return -ENOMEM; + + res = platform_get_resource(pdev, IORESOURCE_MEM, 0); + trng->mem = devm_ioremap_resource(dev, res); + if (IS_ERR(trng->mem)) + return PTR_ERR(trng->mem); + + /* + * the trng needs to be reset first which might not happen in time, + * hence we incorporate a small delay to ensure proper behaviour + */ + writel(HOST_TO_TRNG_RESET, trng->mem + CONTROL_REG); + usleep_range(100, 200); + + if (readl(trng->mem + STATUS_REG) != TRNG_ACK_RESET) { + /* + * there is a small chance the trng is just not ready yet, + * so we try one more time. If the second time fails, we give up + */ + usleep_range(100, 200); + if (readl(trng->mem + STATUS_REG) != TRNG_ACK_RESET) { + dev_err(dev, "failed to reset the trng ip\n"); + return -ENODEV; + } + } + + /* + * once again, to ensure proper behaviour we sleep + * for a while after zeroizing the trng + */ + writel(HOST_TO_TRNG_RELEASE_RESET, trng->mem + CONTROL_REG); + writel(HOST_TO_TRNG_ENABLE, trng->mem + CONTROL_REG); + writel(HOST_TO_TRNG_ZEROIZE, trng->mem + CONTROL_REG); + msleep(20); + + if (readl(trng->mem + STATUS_REG) != TRNG_SUCCESSFUL_STARTUP) { + /* diagnose the reason for the failure */ + if (readl(trng->mem + STATUS_REG) == TRNG_FAILED_STARTUP) { + dev_err(dev, "trng ip startup-tests failed\n"); + return -ENODEV; + } + dev_err(dev, "startup-tests yielded no response\n"); + return -ENODEV; + } + + writel(HOST_TO_TRNG_ACK_ZEROIZE, trng->mem + CONTROL_REG); + + trng->rng.name = pdev->name; + trng->rng.read = xiphera_trng_read; + trng->rng.quality = 900; + + ret = devm_hwrng_register(dev, &trng->rng); + if (ret) { + dev_err(dev, "failed to register rng device: %d\n", ret); + return ret; + } + + platform_set_drvdata(pdev, trng); + + return 0; +} + +static const struct of_device_id xiphera_trng_of_match[] = { + { .compatible = "xiphera,xip8001b-trng", }, + {}, +}; +MODULE_DEVICE_TABLE(of, xiphera_trng_of_match); + +static struct platform_driver xiphera_trng_driver = { + .driver = { + .name = "xiphera-trng", + .of_match_table = xiphera_trng_of_match, + }, + .probe = xiphera_trng_probe, +}; + +module_platform_driver(xiphera_trng_driver); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Atte Tommiska"); +MODULE_DESCRIPTION("Xiphera FPGA-based true random number generator driver"); |