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/platform_device.h> 17 #include <linux/slab.h> 18 19 #define RNGCON 0x04 20 #define TRNGEN BIT(8) 21 #define TRNGMOD BIT(11) 22 #define RNGSEED1 0x18 23 #define RNGSEED2 0x1C 24 #define RNGRCNT 0x20 25 #define RCNT_MASK 0x7F 26 27 struct pic32_rng { 28 void __iomem *base; 29 struct hwrng rng; 30 }; 31 32 /* 33 * The TRNG can generate up to 24Mbps. This is a timeout that should be safe 34 * enough given the instructions in the loop and that the TRNG may not always 35 * be at maximum rate. 36 */ 37 #define RNG_TIMEOUT 500 38 39 static int pic32_rng_init(struct hwrng *rng) 40 { 41 struct pic32_rng *priv = container_of(rng, struct pic32_rng, rng); 42 43 /* enable TRNG in enhanced mode */ 44 writel(TRNGEN | TRNGMOD, priv->base + RNGCON); 45 return 0; 46 } 47 48 static int pic32_rng_read(struct hwrng *rng, void *buf, size_t max, 49 bool wait) 50 { 51 struct pic32_rng *priv = container_of(rng, struct pic32_rng, rng); 52 u64 *data = buf; 53 u32 t; 54 unsigned int timeout = RNG_TIMEOUT; 55 56 do { 57 t = readl(priv->base + RNGRCNT) & RCNT_MASK; 58 if (t == 64) { 59 /* TRNG value comes through the seed registers */ 60 *data = ((u64)readl(priv->base + RNGSEED2) << 32) + 61 readl(priv->base + RNGSEED1); 62 return 8; 63 } 64 } while (wait && --timeout); 65 66 return -EIO; 67 } 68 69 static void pic32_rng_cleanup(struct hwrng *rng) 70 { 71 struct pic32_rng *priv = container_of(rng, struct pic32_rng, rng); 72 73 writel(0, priv->base + RNGCON); 74 } 75 76 static int pic32_rng_probe(struct platform_device *pdev) 77 { 78 struct pic32_rng *priv; 79 struct clk *clk; 80 81 priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL); 82 if (!priv) 83 return -ENOMEM; 84 85 priv->base = devm_platform_ioremap_resource(pdev, 0); 86 if (IS_ERR(priv->base)) 87 return PTR_ERR(priv->base); 88 89 clk = devm_clk_get_enabled(&pdev->dev, NULL); 90 if (IS_ERR(clk)) 91 return PTR_ERR(clk); 92 93 priv->rng.name = pdev->name; 94 priv->rng.init = pic32_rng_init; 95 priv->rng.read = pic32_rng_read; 96 priv->rng.cleanup = pic32_rng_cleanup; 97 98 return devm_hwrng_register(&pdev->dev, &priv->rng); 99 } 100 101 static const struct of_device_id pic32_rng_of_match[] __maybe_unused = { 102 { .compatible = "microchip,pic32mzda-rng", }, 103 { /* sentinel */ } 104 }; 105 MODULE_DEVICE_TABLE(of, pic32_rng_of_match); 106 107 static struct platform_driver pic32_rng_driver = { 108 .probe = pic32_rng_probe, 109 .driver = { 110 .name = "pic32-rng", 111 .of_match_table = pic32_rng_of_match, 112 }, 113 }; 114 115 module_platform_driver(pic32_rng_driver); 116 117 MODULE_LICENSE("GPL"); 118 MODULE_AUTHOR("Joshua Henderson <joshua.henderson@microchip.com>"); 119 MODULE_DESCRIPTION("Microchip PIC32 RNG Driver"); 120