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1// SPDX-License-Identifier: GPL-2.0-or-later OR MIT2/*3 * Copyright (c) 2023 David Yang4 */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 0x016#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 0x421#define RNG_STAT 0x822#define DATA_COUNT GENMASK(2, 0) /* max 4 */23 24struct histb_rng_priv {25 struct hwrng rng;26 void __iomem *base;27};28 29/*30 * Observed:31 * depth = 1 -> ~1ms32 * depth = 255 -> ~16ms33 */34static 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 42static 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 60static 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 81static unsigned int histb_rng_get_depth(void __iomem *base)82{83 return (readl_relaxed(base + RNG_CTRL) & POST_PROCESS_DEPTH) >> 8;84}85 86static ssize_t87depth_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 95static ssize_t96depth_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 110static DEVICE_ATTR_RW(depth);111 112static struct attribute *histb_rng_attrs[] = {113 &dev_attr_depth.attr,114 NULL,115};116 117ATTRIBUTE_GROUPS(histb_rng);118 119static 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 154static const struct of_device_id histb_rng_of_match[] = {155 { .compatible = "hisilicon,histb-rng", },156 { }157};158MODULE_DEVICE_TABLE(of, histb_rng_of_match);159 160static 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 169module_platform_driver(histb_rng_driver);170 171MODULE_DESCRIPTION("Hisilicon STB random number generator driver");172MODULE_LICENSE("Dual MIT/GPL");173MODULE_AUTHOR("David Yang <mmyangfl@gmail.com>");174