1/* 2 * Nomadik RNG support 3 * Copyright 2009 Alessandro Rubini 4 * 5 * This program is free software; you can redistribute it and/or modify 6 * it under the terms of the GNU General Public License as published by 7 * the Free Software Foundation; either version 2 of the License, or 8 * (at your option) any later version. 9 */ 10 11#include <linux/kernel.h> 12#include <linux/module.h> 13#include <linux/init.h> 14#include <linux/device.h> 15#include <linux/amba/bus.h> 16#include <linux/hw_random.h> 17#include <linux/io.h> 18#include <linux/clk.h> 19#include <linux/err.h> 20 21static struct clk *rng_clk; 22 23static int nmk_rng_read(struct hwrng *rng, void *data, size_t max, bool wait) 24{ 25 void __iomem *base = (void __iomem *)rng->priv; 26 27 /* 28 * The register is 32 bits and gives 16 random bits (low half). 29 * A subsequent read will delay the core for 400ns, so we just read 30 * once and accept the very unlikely very small delay, even if wait==0. 31 */ 32 *(u16 *)data = __raw_readl(base + 8) & 0xffff; 33 return 2; 34} 35 36/* we have at most one RNG per machine, granted */ 37static struct hwrng nmk_rng = { 38 .name = "nomadik", 39 .read = nmk_rng_read, 40}; 41 42static int nmk_rng_probe(struct amba_device *dev, struct amba_id *id) 43{ 44 void __iomem *base; 45 int ret; 46 47 rng_clk = clk_get(&dev->dev, NULL); 48 if (IS_ERR(rng_clk)) { 49 dev_err(&dev->dev, "could not get rng clock\n"); 50 ret = PTR_ERR(rng_clk); 51 return ret; 52 } 53 54 clk_enable(rng_clk); 55 56 ret = amba_request_regions(dev, dev->dev.init_name); 57 if (ret) 58 return ret; 59 ret = -ENOMEM; 60 base = ioremap(dev->res.start, resource_size(&dev->res)); 61 if (!base) 62 goto out_release; 63 nmk_rng.priv = (unsigned long)base; 64 ret = hwrng_register(&nmk_rng); 65 if (ret) 66 goto out_unmap; 67 return 0; 68 69out_unmap: 70 iounmap(base); 71out_release: 72 amba_release_regions(dev); 73 clk_disable(rng_clk); 74 clk_put(rng_clk); 75 return ret; 76} 77 78static int nmk_rng_remove(struct amba_device *dev) 79{ 80 void __iomem *base = (void __iomem *)nmk_rng.priv; 81 hwrng_unregister(&nmk_rng); 82 iounmap(base); 83 amba_release_regions(dev); 84 clk_disable(rng_clk); 85 clk_put(rng_clk); 86 return 0; 87} 88 89static struct amba_id nmk_rng_ids[] = { 90 { 91 .id = 0x000805e1, 92 .mask = 0x000fffff, /* top bits are rev and cfg: accept all */ 93 }, 94 {0, 0}, 95}; 96 97static struct amba_driver nmk_rng_driver = { 98 .drv = { 99 .owner = THIS_MODULE, 100 .name = "rng", 101 }, 102 .probe = nmk_rng_probe, 103 .remove = nmk_rng_remove, 104 .id_table = nmk_rng_ids, 105}; 106 107static int __init nmk_rng_init(void) 108{ 109 return amba_driver_register(&nmk_rng_driver); 110} 111 112static void __devexit nmk_rng_exit(void) 113{ 114 amba_driver_unregister(&nmk_rng_driver); 115} 116 117module_init(nmk_rng_init); 118module_exit(nmk_rng_exit); 119 120MODULE_LICENSE("GPL"); 121