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/mod_devicetable.h> 12 #include <linux/module.h> 13 #include <linux/platform_device.h> 14 15 #define RNG_CTRL 0x0 16 #define RNG_SOURCE GENMASK(1, 0) 17 #define DROP_ENABLE BIT(5) 18 #define POST_PROCESS_ENABLE BIT(7) 19 #define POST_PROCESS_DEPTH GENMASK(15, 8) 20 #define RNG_NUMBER 0x4 21 #define RNG_STAT 0x8 22 #define DATA_COUNT GENMASK(2, 0) /* max 4 */ 23 24 struct histb_rng_priv { 25 struct hwrng rng; 26 void __iomem *base; 27 }; 28 29 /* 30 * Observed: 31 * depth = 1 -> ~1ms 32 * depth = 255 -> ~16ms 33 */ 34 static int histb_rng_wait(void __iomem *base) 35 { 36 u32 val; 37 38 return readl_relaxed_poll_timeout(base + RNG_STAT, val, 39 val & DATA_COUNT, 1000, 30 * 1000); 40 } 41 42 static void histb_rng_init(void __iomem *base, unsigned int depth) 43 { 44 u32 val; 45 46 val = readl_relaxed(base + RNG_CTRL); 47 48 val &= ~RNG_SOURCE; 49 val |= 2; 50 51 val &= ~POST_PROCESS_DEPTH; 52 val |= min(depth, 0xffu) << 8; 53 54 val |= POST_PROCESS_ENABLE; 55 val |= DROP_ENABLE; 56 57 writel_relaxed(val, base + RNG_CTRL); 58 } 59 60 static int histb_rng_read(struct hwrng *rng, void *data, size_t max, bool wait) 61 { 62 struct histb_rng_priv *priv = container_of(rng, typeof(*priv), rng); 63 void __iomem *base = priv->base; 64 65 for (int i = 0; i < max; i += sizeof(u32)) { 66 if (!(readl_relaxed(base + RNG_STAT) & DATA_COUNT)) { 67 if (!wait) 68 return i; 69 if (histb_rng_wait(base)) { 70 pr_err("failed to generate random number, generated %d\n", 71 i); 72 return i ? i : -ETIMEDOUT; 73 } 74 } 75 *(u32 *) (data + i) = readl_relaxed(base + RNG_NUMBER); 76 } 77 78 return max; 79 } 80 81 static unsigned int histb_rng_get_depth(void __iomem *base) 82 { 83 return (readl_relaxed(base + RNG_CTRL) & POST_PROCESS_DEPTH) >> 8; 84 } 85 86 static ssize_t 87 depth_show(struct device *dev, struct device_attribute *attr, char *buf) 88 { 89 struct histb_rng_priv *priv = dev_get_drvdata(dev); 90 void __iomem *base = priv->base; 91 92 return sprintf(buf, "%d\n", histb_rng_get_depth(base)); 93 } 94 95 static ssize_t 96 depth_store(struct device *dev, struct device_attribute *attr, 97 const char *buf, size_t count) 98 { 99 struct histb_rng_priv *priv = dev_get_drvdata(dev); 100 void __iomem *base = priv->base; 101 unsigned int depth; 102 103 if (kstrtouint(buf, 0, &depth)) 104 return -ERANGE; 105 106 histb_rng_init(base, depth); 107 return count; 108 } 109 110 static DEVICE_ATTR_RW(depth); 111 112 static struct attribute *histb_rng_attrs[] = { 113 &dev_attr_depth.attr, 114 NULL, 115 }; 116 117 ATTRIBUTE_GROUPS(histb_rng); 118 119 static int histb_rng_probe(struct platform_device *pdev) 120 { 121 struct device *dev = &pdev->dev; 122 struct histb_rng_priv *priv; 123 void __iomem *base; 124 int ret; 125 126 priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL); 127 if (!priv) 128 return -ENOMEM; 129 130 base = devm_platform_ioremap_resource(pdev, 0); 131 if (IS_ERR(base)) 132 return PTR_ERR(base); 133 134 histb_rng_init(base, 144); 135 if (histb_rng_wait(base)) { 136 dev_err(dev, "cannot bring up device\n"); 137 return -ENODEV; 138 } 139 140 priv->base = base; 141 priv->rng.name = pdev->name; 142 priv->rng.read = histb_rng_read; 143 ret = devm_hwrng_register(dev, &priv->rng); 144 if (ret) { 145 dev_err(dev, "failed to register hwrng: %d\n", ret); 146 return ret; 147 } 148 149 platform_set_drvdata(pdev, priv); 150 dev_set_drvdata(dev, priv); 151 return 0; 152 } 153 154 static const struct of_device_id histb_rng_of_match[] = { 155 { .compatible = "hisilicon,histb-rng", }, 156 { } 157 }; 158 MODULE_DEVICE_TABLE(of, histb_rng_of_match); 159 160 static struct platform_driver histb_rng_driver = { 161 .probe = histb_rng_probe, 162 .driver = { 163 .name = "histb-rng", 164 .of_match_table = histb_rng_of_match, 165 .dev_groups = histb_rng_groups, 166 }, 167 }; 168 169 module_platform_driver(histb_rng_driver); 170 171 MODULE_DESCRIPTION("Hisilicon STB random number generator driver"); 172 MODULE_LICENSE("Dual MIT/GPL"); 173 MODULE_AUTHOR("David Yang <mmyangfl@gmail.com>"); 174