drivers/char/hw_random/geode-rng.c

   1 /*
   2  * RNG driver for AMD Geode RNGs
   3  *
   4  * Copyright 2005 (c) MontaVista Software, Inc.
   5  *
   6  * with the majority of the code coming from:
   7  *
   8  * Hardware driver for the Intel/AMD/VIA Random Number Generators (RNG)
   9  * (c) Copyright 2003 Red Hat Inc <jgarzik@redhat.com>
  10  *
  11  * derived from
  12  *
  13  * Hardware driver for the AMD 768 Random Number Generator (RNG)
  14  * (c) Copyright 2001 Red Hat Inc
  15  *
  16  * derived from
  17  *
  18  * Hardware driver for Intel i810 Random Number Generator (RNG)
  19  * Copyright 2000,2001 Jeff Garzik <jgarzik@pobox.com>
  20  * Copyright 2000,2001 Philipp Rumpf <prumpf@mandrakesoft.com>
  21  *
  22  * This file is licensed under  the terms of the GNU General Public
  23  * License version 2. This program is licensed "as is" without any
  24  * warranty of any kind, whether express or implied.
  25  */
  26
  27 #include <linux/delay.h>
  28 #include <linux/hw_random.h>
  29 #include <linux/io.h>
  30 #include <linux/kernel.h>
  31 #include <linux/module.h>
  32 #include <linux/pci.h>
  33
  34
  35 #define PFX     KBUILD_MODNAME ": "
  36
  37 #define GEODE_RNG_DATA_REG   0x50
  38 #define GEODE_RNG_STATUS_REG 0x54
  39
  40 /*
  41  * Data for PCI driver interface
  42  *
  43  * This data only exists for exporting the supported
  44  * PCI ids via MODULE_DEVICE_TABLE.  We do not actually
  45  * register a pci_driver, because someone else might one day
  46  * want to register another driver on the same PCI id.
  47  */
  48 static const struct pci_device_id pci_tbl[] = {
  49         { PCI_VDEVICE(AMD, PCI_DEVICE_ID_AMD_LX_AES), 0, },
  50         { 0, }, /* terminate list */
  51 };
  52 MODULE_DEVICE_TABLE(pci, pci_tbl);
  53
  54
  55 static int geode_rng_data_read(struct hwrng *rng, u32 *data)
  56 {
  57         void __iomem *mem = (void __iomem *)rng->priv;
  58
  59         *data = readl(mem + GEODE_RNG_DATA_REG);
  60
  61         return 4;
  62 }
  63
  64 static int geode_rng_data_present(struct hwrng *rng, int wait)
  65 {
  66         void __iomem *mem = (void __iomem *)rng->priv;
  67         int data, i;
  68
  69         for (i = 0; i < 20; i++) {
  70                 data = !!(readl(mem + GEODE_RNG_STATUS_REG));
  71                 if (data || !wait)
  72                         break;
  73                 udelay(10);
  74         }
  75         return data;
  76 }
  77
  78
  79 static struct hwrng geode_rng = {
  80         .name           = "geode",
  81         .data_present   = geode_rng_data_present,
  82         .data_read      = geode_rng_data_read,
  83 };
  84
  85
  86 static int __init mod_init(void)
  87 {
  88         int err = -ENODEV;
  89         struct pci_dev *pdev = NULL;
  90         const struct pci_device_id *ent;
  91         void __iomem *mem;
  92         unsigned long rng_base;
  93
  94         for_each_pci_dev(pdev) {
  95                 ent = pci_match_id(pci_tbl, pdev);
  96                 if (ent)
  97                         goto found;
  98         }
  99         /* Device not found. */
 100         goto out;
 101
 102 found:
 103         rng_base = pci_resource_start(pdev, 0);
 104         if (rng_base == 0)
 105                 goto out;
 106         err = -ENOMEM;
 107         mem = ioremap(rng_base, 0x58);
 108         if (!mem)
 109                 goto out;
 110         geode_rng.priv = (unsigned long)mem;
 111
 112         pr_info("AMD Geode RNG detected\n");
 113         err = hwrng_register(&geode_rng);
 114         if (err) {
 115                 pr_err(PFX "RNG registering failed (%d)\n",
 116                        err);
 117                 goto err_unmap;
 118         }
 119 out:
 120         return err;
 121
 122 err_unmap:
 123         iounmap(mem);
 124         goto out;
 125 }
 126
 127 static void __exit mod_exit(void)
 128 {
 129         void __iomem *mem = (void __iomem *)geode_rng.priv;
 130
 131         hwrng_unregister(&geode_rng);
 132         iounmap(mem);
 133 }
 134
 135 module_init(mod_init);
 136 module_exit(mod_exit);
 137
 138 MODULE_DESCRIPTION("H/W RNG driver for AMD Geode LX CPUs");
 139 MODULE_LICENSE("GPL");