char/hw_random/geode-rng.c

0001 /*
0002  * RNG driver for AMD Geode RNGs
0003  *
0004  * Copyright 2005 (c) MontaVista Software, Inc.
0005  *
0006  * with the majority of the code coming from:
0007  *
0008  * Hardware driver for the Intel/AMD/VIA Random Number Generators (RNG)
0009  * (c) Copyright 2003 Red Hat Inc <jgarzik@redhat.com>
0010  *
0011  * derived from
0012  *
0013  * Hardware driver for the AMD 768 Random Number Generator (RNG)
0014  * (c) Copyright 2001 Red Hat Inc
0015  *
0016  * derived from
0017  *
0018  * Hardware driver for Intel i810 Random Number Generator (RNG)
0019  * Copyright 2000,2001 Jeff Garzik <jgarzik@pobox.com>
0020  * Copyright 2000,2001 Philipp Rumpf <prumpf@mandrakesoft.com>
0021  *
0022  * This file is licensed under  the terms of the GNU General Public
0023  * License version 2. This program is licensed "as is" without any
0024  * warranty of any kind, whether express or implied.
0025  */
0026
0027 #include <linux/delay.h>
0028 #include <linux/hw_random.h>
0029 #include <linux/io.h>
0030 #include <linux/kernel.h>
0031 #include <linux/module.h>
0032 #include <linux/pci.h>
0033
0034
0035 #define PFX KBUILD_MODNAME ": "
0036
0037 #define GEODE_RNG_DATA_REG   0x50
0038 #define GEODE_RNG_STATUS_REG 0x54
0039
0040 /*
0041  * Data for PCI driver interface
0042  *
0043  * This data only exists for exporting the supported
0044  * PCI ids via MODULE_DEVICE_TABLE.  We do not actually
0045  * register a pci_driver, because someone else might one day
0046  * want to register another driver on the same PCI id.
0047  */
0048 static const struct pci_device_id pci_tbl[] = {
0049     { PCI_VDEVICE(AMD, PCI_DEVICE_ID_AMD_LX_AES), 0, },
0050     { 0, }, /* terminate list */
0051 };
0052 MODULE_DEVICE_TABLE(pci, pci_tbl);
0053
0054
0055 static int geode_rng_data_read(struct hwrng *rng, u32 *data)
0056 {
0057     void __iomem *mem = (void __iomem *)rng->priv;
0058
0059     *data = readl(mem + GEODE_RNG_DATA_REG);
0060
0061     return 4;
0062 }
0063
0064 static int geode_rng_data_present(struct hwrng *rng, int wait)
0065 {
0066     void __iomem *mem = (void __iomem *)rng->priv;
0067     int data, i;
0068
0069     for (i = 0; i < 20; i++) {
0070         data = !!(readl(mem + GEODE_RNG_STATUS_REG));
0071         if (data || !wait)
0072             break;
0073         udelay(10);
0074     }
0075     return data;
0076 }
0077
0078
0079 static struct hwrng geode_rng = {
0080     .name       = "geode",
0081     .data_present   = geode_rng_data_present,
0082     .data_read  = geode_rng_data_read,
0083 };
0084
0085
0086 static int __init geode_rng_init(void)
0087 {
0088     int err = -ENODEV;
0089     struct pci_dev *pdev = NULL;
0090     const struct pci_device_id *ent;
0091     void __iomem *mem;
0092     unsigned long rng_base;
0093
0094     for_each_pci_dev(pdev) {
0095         ent = pci_match_id(pci_tbl, pdev);
0096         if (ent)
0097             goto found;
0098     }
0099     /* Device not found. */
0100     goto out;
0101
0102 found:
0103     rng_base = pci_resource_start(pdev, 0);
0104     if (rng_base == 0)
0105         goto out;
0106     err = -ENOMEM;
0107     mem = ioremap(rng_base, 0x58);
0108     if (!mem)
0109         goto out;
0110     geode_rng.priv = (unsigned long)mem;
0111
0112     pr_info("AMD Geode RNG detected\n");
0113     err = hwrng_register(&geode_rng);
0114     if (err) {
0115         pr_err(PFX "RNG registering failed (%d)\n",
0116                err);
0117         goto err_unmap;
0118     }
0119 out:
0120     return err;
0121
0122 err_unmap:
0123     iounmap(mem);
0124     goto out;
0125 }
0126
0127 static void __exit geode_rng_exit(void)
0128 {
0129     void __iomem *mem = (void __iomem *)geode_rng.priv;
0130
0131     hwrng_unregister(&geode_rng);
0132     iounmap(mem);
0133 }
0134
0135 module_init(geode_rng_init);
0136 module_exit(geode_rng_exit);
0137
0138 MODULE_DESCRIPTION("H/W RNG driver for AMD Geode LX CPUs");
0139 MODULE_LICENSE("GPL");