pic32-rng.c (3194B)
1// SPDX-License-Identifier: GPL-2.0-only 2/* 3 * PIC32 RNG driver 4 * 5 * Joshua Henderson <joshua.henderson@microchip.com> 6 * Copyright (C) 2016 Microchip Technology Inc. All rights reserved. 7 */ 8 9#include <linux/clk.h> 10#include <linux/clkdev.h> 11#include <linux/err.h> 12#include <linux/hw_random.h> 13#include <linux/io.h> 14#include <linux/kernel.h> 15#include <linux/module.h> 16#include <linux/of.h> 17#include <linux/of_device.h> 18#include <linux/platform_device.h> 19#include <linux/slab.h> 20 21#define RNGCON 0x04 22#define TRNGEN BIT(8) 23#define PRNGEN BIT(9) 24#define PRNGCONT BIT(10) 25#define TRNGMOD BIT(11) 26#define SEEDLOAD BIT(12) 27#define RNGPOLY1 0x08 28#define RNGPOLY2 0x0C 29#define RNGNUMGEN1 0x10 30#define RNGNUMGEN2 0x14 31#define RNGSEED1 0x18 32#define RNGSEED2 0x1C 33#define RNGRCNT 0x20 34#define RCNT_MASK 0x7F 35 36struct pic32_rng { 37 void __iomem *base; 38 struct hwrng rng; 39 struct clk *clk; 40}; 41 42/* 43 * The TRNG can generate up to 24Mbps. This is a timeout that should be safe 44 * enough given the instructions in the loop and that the TRNG may not always 45 * be at maximum rate. 46 */ 47#define RNG_TIMEOUT 500 48 49static int pic32_rng_read(struct hwrng *rng, void *buf, size_t max, 50 bool wait) 51{ 52 struct pic32_rng *priv = container_of(rng, struct pic32_rng, rng); 53 u64 *data = buf; 54 u32 t; 55 unsigned int timeout = RNG_TIMEOUT; 56 57 do { 58 t = readl(priv->base + RNGRCNT) & RCNT_MASK; 59 if (t == 64) { 60 /* TRNG value comes through the seed registers */ 61 *data = ((u64)readl(priv->base + RNGSEED2) << 32) + 62 readl(priv->base + RNGSEED1); 63 return 8; 64 } 65 } while (wait && --timeout); 66 67 return -EIO; 68} 69 70static int pic32_rng_probe(struct platform_device *pdev) 71{ 72 struct pic32_rng *priv; 73 u32 v; 74 int ret; 75 76 priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL); 77 if (!priv) 78 return -ENOMEM; 79 80 priv->base = devm_platform_ioremap_resource(pdev, 0); 81 if (IS_ERR(priv->base)) 82 return PTR_ERR(priv->base); 83 84 priv->clk = devm_clk_get(&pdev->dev, NULL); 85 if (IS_ERR(priv->clk)) 86 return PTR_ERR(priv->clk); 87 88 ret = clk_prepare_enable(priv->clk); 89 if (ret) 90 return ret; 91 92 /* enable TRNG in enhanced mode */ 93 v = TRNGEN | TRNGMOD; 94 writel(v, priv->base + RNGCON); 95 96 priv->rng.name = pdev->name; 97 priv->rng.read = pic32_rng_read; 98 99 ret = devm_hwrng_register(&pdev->dev, &priv->rng); 100 if (ret) 101 goto err_register; 102 103 platform_set_drvdata(pdev, priv); 104 105 return 0; 106 107err_register: 108 clk_disable_unprepare(priv->clk); 109 return ret; 110} 111 112static int pic32_rng_remove(struct platform_device *pdev) 113{ 114 struct pic32_rng *rng = platform_get_drvdata(pdev); 115 116 writel(0, rng->base + RNGCON); 117 clk_disable_unprepare(rng->clk); 118 return 0; 119} 120 121static const struct of_device_id pic32_rng_of_match[] __maybe_unused = { 122 { .compatible = "microchip,pic32mzda-rng", }, 123 { /* sentinel */ } 124}; 125MODULE_DEVICE_TABLE(of, pic32_rng_of_match); 126 127static struct platform_driver pic32_rng_driver = { 128 .probe = pic32_rng_probe, 129 .remove = pic32_rng_remove, 130 .driver = { 131 .name = "pic32-rng", 132 .of_match_table = of_match_ptr(pic32_rng_of_match), 133 }, 134}; 135 136module_platform_driver(pic32_rng_driver); 137 138MODULE_LICENSE("GPL"); 139MODULE_AUTHOR("Joshua Henderson <joshua.henderson@microchip.com>"); 140MODULE_DESCRIPTION("Microchip PIC32 RNG Driver");