1 // SPDX-License-Identifier: GPL-2.0-or-later OR MIT 2 /* 3 * Copyright (c) 2023 David Yang 4 */ 5 6 #include <linux/err.h> 7 #include <linux/hw_random.h> 8 #include <linux/io.h> 9 #include <linux/iopoll.h> 10 #include <linux/kernel.h> 11 #include <linux/module.h> 12 #include <linux/platform_device.h> 13 14 #define RNG_CTRL 0x0 15 #define RNG_SOURCE GENMASK(1, 0) 16 #define DROP_ENABLE BIT(5) 17 #define POST_PROCESS_ENABLE BIT(7) 18 #define POST_PROCESS_DEPTH GENMASK(15, 8) 19 #define RNG_NUMBER 0x4 20 #define RNG_STAT 0x8 21 #define DATA_COUNT GENMASK(2, 0) /* max 4 */ 22 23 struct histb_rng_priv { 24 struct hwrng rng; 25 void __iomem *base; 26 }; 27 28 /* 29 * Observed: 30 * depth = 1 -> ~1ms 31 * depth = 255 -> ~16ms 32 */ 33 static int histb_rng_wait(void __iomem *base) 34 { 35 u32 val; 36 37 return readl_relaxed_poll_timeout(base + RNG_STAT, val, 38 val & DATA_COUNT, 1000, 30 * 1000); 39 } 40 41 static void histb_rng_init(void __iomem *base, unsigned int depth) 42 { 43 u32 val; 44 45 val = readl_relaxed(base + RNG_CTRL); 46 47 val &= ~RNG_SOURCE; 48 val |= 2; 49 50 val &= ~POST_PROCESS_DEPTH; 51 val |= min(depth, 0xffu) << 8; 52 53 val |= POST_PROCESS_ENABLE; 54 val |= DROP_ENABLE; 55 56 writel_relaxed(val, base + RNG_CTRL); 57 } 58 59 static int histb_rng_read(struct hwrng *rng, void *data, size_t max, bool wait) 60 { 61 struct histb_rng_priv *priv = container_of(rng, typeof(*priv), rng); 62 void __iomem *base = priv->base; 63 64 for (int i = 0; i < max; i += sizeof(u32)) { 65 if (!(readl_relaxed(base + RNG_STAT) & DATA_COUNT)) { 66 if (!wait) 67 return i; 68 if (histb_rng_wait(base)) { 69 pr_err("failed to generate random number, generated %d\n", 70 i); 71 return i ? i : -ETIMEDOUT; 72 } 73 } 74 *(u32 *) (data + i) = readl_relaxed(base + RNG_NUMBER); 75 } 76 77 return max; 78 } 79 80 static unsigned int histb_rng_get_depth(void __iomem *base) 81 { 82 return (readl_relaxed(base + RNG_CTRL) & POST_PROCESS_DEPTH) >> 8; 83 } 84 85 static ssize_t 86 depth_show(struct device *dev, struct device_attribute *attr, char *buf) 87 { 88 struct histb_rng_priv *priv = dev_get_drvdata(dev); 89 void __iomem *base = priv->base; 90 91 return sprintf(buf, "%u\n", histb_rng_get_depth(base)); 92 } 93 94 static ssize_t 95 depth_store(struct device *dev, struct device_attribute *attr, 96 const char *buf, size_t count) 97 { 98 struct histb_rng_priv *priv = dev_get_drvdata(dev); 99 void __iomem *base = priv->base; 100 unsigned int depth; 101 102 if (kstrtouint(buf, 0, &depth)) 103 return -ERANGE; 104 105 histb_rng_init(base, depth); 106 return count; 107 } 108 109 static DEVICE_ATTR_RW(depth); 110 111 static struct attribute *histb_rng_attrs[] = { 112 &dev_attr_depth.attr, 113 NULL, 114 }; 115 116 ATTRIBUTE_GROUPS(histb_rng); 117 118 static int histb_rng_probe(struct platform_device *pdev) 119 { 120 struct device *dev = &pdev->dev; 121 struct histb_rng_priv *priv; 122 void __iomem *base; 123 int ret; 124 125 priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL); 126 if (!priv) 127 return -ENOMEM; 128 129 base = devm_platform_ioremap_resource(pdev, 0); 130 if (IS_ERR(base)) 131 return PTR_ERR(base); 132 133 histb_rng_init(base, 144); 134 if (histb_rng_wait(base)) { 135 dev_err(dev, "cannot bring up device\n"); 136 return -ENODEV; 137 } 138 139 priv->base = base; 140 priv->rng.name = pdev->name; 141 priv->rng.read = histb_rng_read; 142 ret = devm_hwrng_register(dev, &priv->rng); 143 if (ret) { 144 dev_err(dev, "failed to register hwrng: %d\n", ret); 145 return ret; 146 } 147 148 platform_set_drvdata(pdev, priv); 149 dev_set_drvdata(dev, priv); 150 return 0; 151 } 152 153 static const struct of_device_id histb_rng_of_match[] = { 154 { .compatible = "hisilicon,histb-rng", }, 155 { } 156 }; 157 MODULE_DEVICE_TABLE(of, histb_rng_of_match); 158 159 static struct platform_driver histb_rng_driver = { 160 .probe = histb_rng_probe, 161 .driver = { 162 .name = "histb-rng", 163 .of_match_table = histb_rng_of_match, 164 .dev_groups = histb_rng_groups, 165 }, 166 }; 167 168 module_platform_driver(histb_rng_driver); 169 170 MODULE_DESCRIPTION("Hisilicon STB random number generator driver"); 171 MODULE_LICENSE("Dual MIT/GPL"); 172 MODULE_AUTHOR("David Yang <mmyangfl@gmail.com>"); 173