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 = devm_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 = devm_ioremap(&dev->dev, dev->res.start, 61 resource_size(&dev->res)); 62 if (!base) 63 goto out_release; 64 nmk_rng.priv = (unsigned long)base; 65 ret = hwrng_register(&nmk_rng); 66 if (ret) 67 goto out_release; 68 return 0; 69 70 out_release: 71 amba_release_regions(dev); 72 out_clk: 73 clk_disable(rng_clk); 74 return ret; 75 } 76 77 static int nmk_rng_remove(struct amba_device *dev) 78 { 79 hwrng_unregister(&nmk_rng); 80 amba_release_regions(dev); 81 clk_disable(rng_clk); 82 return 0; 83 } 84 85 static struct amba_id nmk_rng_ids[] = { 86 { 87 .id = 0x000805e1, 88 .mask = 0x000fffff, /* top bits are rev and cfg: accept all */ 89 }, 90 {0, 0}, 91 }; 92 93 MODULE_DEVICE_TABLE(amba, nmk_rng_ids); 94 95 static struct amba_driver nmk_rng_driver = { 96 .drv = { 97 .owner = THIS_MODULE, 98 .name = "rng", 99 }, 100 .probe = nmk_rng_probe, 101 .remove = nmk_rng_remove, 102 .id_table = nmk_rng_ids, 103 }; 104 105 module_amba_driver(nmk_rng_driver); 106 107 MODULE_LICENSE("GPL"); 108