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/device.h> 14 #include <linux/amba/bus.h> 15 #include <linux/hw_random.h> 16 #include <linux/io.h> 17 #include <linux/clk.h> 18 #include <linux/err.h> 19 20 static struct clk *rng_clk; 21 22 static int nmk_rng_read(struct hwrng *rng, void *data, size_t max, bool wait) 23 { 24 void __iomem *base = (void __iomem *)rng->priv; 25 26 /* 27 * The register is 32 bits and gives 16 random bits (low half). 28 * A subsequent read will delay the core for 400ns, so we just read 29 * once and accept the very unlikely very small delay, even if wait==0. 30 */ 31 *(u16 *)data = __raw_readl(base + 8) & 0xffff; 32 return 2; 33 } 34 35 /* we have at most one RNG per machine, granted */ 36 static struct hwrng nmk_rng = { 37 .name = "nomadik", 38 .read = nmk_rng_read, 39 }; 40 41 static int nmk_rng_probe(struct amba_device *dev, const struct amba_id *id) 42 { 43 void __iomem *base; 44 int ret; 45 46 rng_clk = devm_clk_get(&dev->dev, NULL); 47 if (IS_ERR(rng_clk)) { 48 dev_err(&dev->dev, "could not get rng clock\n"); 49 ret = PTR_ERR(rng_clk); 50 return ret; 51 } 52 53 clk_prepare_enable(rng_clk); 54 55 ret = amba_request_regions(dev, dev->dev.init_name); 56 if (ret) 57 goto out_clk; 58 ret = -ENOMEM; 59 base = devm_ioremap(&dev->dev, dev->res.start, 60 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_release; 67 return 0; 68 69 out_release: 70 amba_release_regions(dev); 71 out_clk: 72 clk_disable(rng_clk); 73 return ret; 74 } 75 76 static int nmk_rng_remove(struct amba_device *dev) 77 { 78 hwrng_unregister(&nmk_rng); 79 amba_release_regions(dev); 80 clk_disable(rng_clk); 81 return 0; 82 } 83 84 static struct amba_id nmk_rng_ids[] = { 85 { 86 .id = 0x000805e1, 87 .mask = 0x000fffff, /* top bits are rev and cfg: accept all */ 88 }, 89 {0, 0}, 90 }; 91 92 MODULE_DEVICE_TABLE(amba, nmk_rng_ids); 93 94 static struct amba_driver nmk_rng_driver = { 95 .drv = { 96 .owner = THIS_MODULE, 97 .name = "rng", 98 }, 99 .probe = nmk_rng_probe, 100 .remove = nmk_rng_remove, 101 .id_table = nmk_rng_ids, 102 }; 103 104 module_amba_driver(nmk_rng_driver); 105 106 MODULE_LICENSE("GPL"); 107