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 21 static struct clk *rng_clk; 22 23 static 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 */ 37 static struct hwrng nmk_rng = { 38 .name = "nomadik", 39 .read = nmk_rng_read, 40 }; 41 42 static int nmk_rng_probe(struct amba_device *dev, const 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_prepare_enable(rng_clk); 55 56 ret = amba_request_regions(dev, dev->dev.init_name); 57 if (ret) 58 goto out_clk; 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 69 out_unmap: 70 iounmap(base); 71 out_release: 72 amba_release_regions(dev); 73 out_clk: 74 clk_disable(rng_clk); 75 clk_put(rng_clk); 76 return ret; 77 } 78 79 static int nmk_rng_remove(struct amba_device *dev) 80 { 81 void __iomem *base = (void __iomem *)nmk_rng.priv; 82 hwrng_unregister(&nmk_rng); 83 iounmap(base); 84 amba_release_regions(dev); 85 clk_disable(rng_clk); 86 clk_put(rng_clk); 87 return 0; 88 } 89 90 static struct amba_id nmk_rng_ids[] = { 91 { 92 .id = 0x000805e1, 93 .mask = 0x000fffff, /* top bits are rev and cfg: accept all */ 94 }, 95 {0, 0}, 96 }; 97 98 MODULE_DEVICE_TABLE(amba, nmk_rng_ids); 99 100 static struct amba_driver nmk_rng_driver = { 101 .drv = { 102 .owner = THIS_MODULE, 103 .name = "rng", 104 }, 105 .probe = nmk_rng_probe, 106 .remove = nmk_rng_remove, 107 .id_table = nmk_rng_ids, 108 }; 109 110 module_amba_driver(nmk_rng_driver); 111 112 MODULE_LICENSE("GPL"); 113