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- // 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;
- trng = devm_kzalloc(dev, sizeof(*trng), GFP_KERNEL);
- if (!trng)
- return -ENOMEM;
- trng->mem = devm_platform_ioremap_resource(pdev, 0);
- 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");
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