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