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