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 struct clk *rng_clk; 17 18 static int nmk_rng_read(struct hwrng *rng, void *data, size_t max, bool wait) 19 { 20 void __iomem *base = (void __iomem *)rng->priv; 21 22 /* 23 * The register is 32 bits and gives 16 random bits (low half). 24 * A subsequent read will delay the core for 400ns, so we just read 25 * once and accept the very unlikely very small delay, even if wait==0. 26 */ 27 *(u16 *)data = __raw_readl(base + 8) & 0xffff; 28 return 2; 29 } 30 31 /* we have at most one RNG per machine, granted */ 32 static struct hwrng nmk_rng = { 33 .name = "nomadik", 34 .read = nmk_rng_read, 35 }; 36 37 static int nmk_rng_probe(struct amba_device *dev, const struct amba_id *id) 38 { 39 void __iomem *base; 40 int ret; 41 42 rng_clk = devm_clk_get(&dev->dev, NULL); 43 if (IS_ERR(rng_clk)) { 44 dev_err(&dev->dev, "could not get rng clock\n"); 45 ret = PTR_ERR(rng_clk); 46 return ret; 47 } 48 49 clk_prepare_enable(rng_clk); 50 51 ret = amba_request_regions(dev, dev->dev.init_name); 52 if (ret) 53 goto out_clk; 54 ret = -ENOMEM; 55 base = devm_ioremap(&dev->dev, dev->res.start, 56 resource_size(&dev->res)); 57 if (!base) 58 goto out_release; 59 nmk_rng.priv = (unsigned long)base; 60 ret = devm_hwrng_register(&dev->dev, &nmk_rng); 61 if (ret) 62 goto out_release; 63 return 0; 64 65 out_release: 66 amba_release_regions(dev); 67 out_clk: 68 clk_disable_unprepare(rng_clk); 69 return ret; 70 } 71 72 static void nmk_rng_remove(struct amba_device *dev) 73 { 74 amba_release_regions(dev); 75 clk_disable_unprepare(rng_clk); 76 } 77 78 static const struct amba_id nmk_rng_ids[] = { 79 { 80 .id = 0x000805e1, 81 .mask = 0x000fffff, /* top bits are rev and cfg: accept all */ 82 }, 83 {0, 0}, 84 }; 85 86 MODULE_DEVICE_TABLE(amba, nmk_rng_ids); 87 88 static struct amba_driver nmk_rng_driver = { 89 .drv = { 90 .owner = THIS_MODULE, 91 .name = "rng", 92 }, 93 .probe = nmk_rng_probe, 94 .remove = nmk_rng_remove, 95 .id_table = nmk_rng_ids, 96 }; 97 98 module_amba_driver(nmk_rng_driver); 99 100 MODULE_LICENSE("GPL"); 101