1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * Nomadik RNG support 4 * Copyright 2009 Alessandro Rubini 5 */ 6 7 #include <linux/kernel.h> 8 #include <linux/module.h> 9 #include <linux/device.h> 10 #include <linux/amba/bus.h> 11 #include <linux/hw_random.h> 12 #include <linux/io.h> 13 #include <linux/clk.h> 14 #include <linux/err.h> 15 16 static int nmk_rng_read(struct hwrng *rng, void *data, size_t max, bool wait) 17 { 18 void __iomem *base = (void __iomem *)rng->priv; 19 20 /* 21 * The register is 32 bits and gives 16 random bits (low half). 22 * A subsequent read will delay the core for 400ns, so we just read 23 * once and accept the very unlikely very small delay, even if wait==0. 24 */ 25 *(u16 *)data = __raw_readl(base + 8) & 0xffff; 26 return 2; 27 } 28 29 /* we have at most one RNG per machine, granted */ 30 static struct hwrng nmk_rng = { 31 .name = "nomadik", 32 .read = nmk_rng_read, 33 }; 34 35 static int nmk_rng_probe(struct amba_device *dev, const struct amba_id *id) 36 { 37 struct clk *rng_clk; 38 void __iomem *base; 39 int ret; 40 41 rng_clk = devm_clk_get_enabled(&dev->dev, NULL); 42 if (IS_ERR(rng_clk)) { 43 dev_err(&dev->dev, "could not get rng clock\n"); 44 ret = PTR_ERR(rng_clk); 45 return ret; 46 } 47 48 ret = amba_request_regions(dev, dev->dev.init_name); 49 if (ret) 50 return ret; 51 ret = -ENOMEM; 52 base = devm_ioremap(&dev->dev, dev->res.start, 53 resource_size(&dev->res)); 54 if (!base) 55 goto out_release; 56 nmk_rng.priv = (unsigned long)base; 57 ret = devm_hwrng_register(&dev->dev, &nmk_rng); 58 if (ret) 59 goto out_release; 60 return 0; 61 62 out_release: 63 amba_release_regions(dev); 64 return ret; 65 } 66 67 static void nmk_rng_remove(struct amba_device *dev) 68 { 69 amba_release_regions(dev); 70 } 71 72 static const struct amba_id nmk_rng_ids[] = { 73 { 74 .id = 0x000805e1, 75 .mask = 0x000fffff, /* top bits are rev and cfg: accept all */ 76 }, 77 {0, 0}, 78 }; 79 80 MODULE_DEVICE_TABLE(amba, nmk_rng_ids); 81 82 static struct amba_driver nmk_rng_driver = { 83 .drv = { 84 .owner = THIS_MODULE, 85 .name = "rng", 86 }, 87 .probe = nmk_rng_probe, 88 .remove = nmk_rng_remove, 89 .id_table = nmk_rng_ids, 90 }; 91 92 module_amba_driver(nmk_rng_driver); 93 94 MODULE_LICENSE("GPL"); 95