1 // SPDX-License-Identifier: GPL-2.0 2 /* Copyright (C) 2020 Xiphera Ltd. */ 3 4 #include <linux/kernel.h> 5 #include <linux/module.h> 6 #include <linux/mod_devicetable.h> 7 #include <linux/err.h> 8 #include <linux/io.h> 9 #include <linux/hw_random.h> 10 #include <linux/of_device.h> 11 #include <linux/platform_device.h> 12 #include <linux/delay.h> 13 14 #define CONTROL_REG 0x00000000 15 #define STATUS_REG 0x00000004 16 #define RAND_REG 0x00000000 17 18 #define HOST_TO_TRNG_RESET 0x00000001 19 #define HOST_TO_TRNG_RELEASE_RESET 0x00000002 20 #define HOST_TO_TRNG_ENABLE 0x80000000 21 #define HOST_TO_TRNG_ZEROIZE 0x80000004 22 #define HOST_TO_TRNG_ACK_ZEROIZE 0x80000008 23 #define HOST_TO_TRNG_READ 0x8000000F 24 25 /* trng statuses */ 26 #define TRNG_ACK_RESET 0x000000AC 27 #define TRNG_SUCCESSFUL_STARTUP 0x00000057 28 #define TRNG_FAILED_STARTUP 0x000000FA 29 #define TRNG_NEW_RAND_AVAILABLE 0x000000ED 30 31 struct xiphera_trng { 32 void __iomem *mem; 33 struct hwrng rng; 34 }; 35 36 static int xiphera_trng_read(struct hwrng *rng, void *buf, size_t max, bool wait) 37 { 38 struct xiphera_trng *trng = container_of(rng, struct xiphera_trng, rng); 39 int ret = 0; 40 41 while (max >= sizeof(u32)) { 42 /* check for data */ 43 if (readl(trng->mem + STATUS_REG) == TRNG_NEW_RAND_AVAILABLE) { 44 *(u32 *)buf = readl(trng->mem + RAND_REG); 45 /* 46 * Inform the trng of the read 47 * and re-enable it to produce a new random number 48 */ 49 writel(HOST_TO_TRNG_READ, trng->mem + CONTROL_REG); 50 writel(HOST_TO_TRNG_ENABLE, trng->mem + CONTROL_REG); 51 ret += sizeof(u32); 52 buf += sizeof(u32); 53 max -= sizeof(u32); 54 } else { 55 break; 56 } 57 } 58 return ret; 59 } 60 61 static int xiphera_trng_probe(struct platform_device *pdev) 62 { 63 int ret; 64 struct xiphera_trng *trng; 65 struct device *dev = &pdev->dev; 66 67 trng = devm_kzalloc(dev, sizeof(*trng), GFP_KERNEL); 68 if (!trng) 69 return -ENOMEM; 70 71 trng->mem = devm_platform_ioremap_resource(pdev, 0); 72 if (IS_ERR(trng->mem)) 73 return PTR_ERR(trng->mem); 74 75 /* 76 * the trng needs to be reset first which might not happen in time, 77 * hence we incorporate a small delay to ensure proper behaviour 78 */ 79 writel(HOST_TO_TRNG_RESET, trng->mem + CONTROL_REG); 80 usleep_range(100, 200); 81 82 if (readl(trng->mem + STATUS_REG) != TRNG_ACK_RESET) { 83 /* 84 * there is a small chance the trng is just not ready yet, 85 * so we try one more time. If the second time fails, we give up 86 */ 87 usleep_range(100, 200); 88 if (readl(trng->mem + STATUS_REG) != TRNG_ACK_RESET) { 89 dev_err(dev, "failed to reset the trng ip\n"); 90 return -ENODEV; 91 } 92 } 93 94 /* 95 * once again, to ensure proper behaviour we sleep 96 * for a while after zeroizing the trng 97 */ 98 writel(HOST_TO_TRNG_RELEASE_RESET, trng->mem + CONTROL_REG); 99 writel(HOST_TO_TRNG_ENABLE, trng->mem + CONTROL_REG); 100 writel(HOST_TO_TRNG_ZEROIZE, trng->mem + CONTROL_REG); 101 msleep(20); 102 103 if (readl(trng->mem + STATUS_REG) != TRNG_SUCCESSFUL_STARTUP) { 104 /* diagnose the reason for the failure */ 105 if (readl(trng->mem + STATUS_REG) == TRNG_FAILED_STARTUP) { 106 dev_err(dev, "trng ip startup-tests failed\n"); 107 return -ENODEV; 108 } 109 dev_err(dev, "startup-tests yielded no response\n"); 110 return -ENODEV; 111 } 112 113 writel(HOST_TO_TRNG_ACK_ZEROIZE, trng->mem + CONTROL_REG); 114 115 trng->rng.name = pdev->name; 116 trng->rng.read = xiphera_trng_read; 117 trng->rng.quality = 900; 118 119 ret = devm_hwrng_register(dev, &trng->rng); 120 if (ret) { 121 dev_err(dev, "failed to register rng device: %d\n", ret); 122 return ret; 123 } 124 125 platform_set_drvdata(pdev, trng); 126 127 return 0; 128 } 129 130 static const struct of_device_id xiphera_trng_of_match[] = { 131 { .compatible = "xiphera,xip8001b-trng", }, 132 {}, 133 }; 134 MODULE_DEVICE_TABLE(of, xiphera_trng_of_match); 135 136 static struct platform_driver xiphera_trng_driver = { 137 .driver = { 138 .name = "xiphera-trng", 139 .of_match_table = xiphera_trng_of_match, 140 }, 141 .probe = xiphera_trng_probe, 142 }; 143 144 module_platform_driver(xiphera_trng_driver); 145 146 MODULE_LICENSE("GPL"); 147 MODULE_AUTHOR("Atte Tommiska"); 148 MODULE_DESCRIPTION("Xiphera FPGA-based true random number generator driver"); 149