drivers/char/hw_random/intel-rng.c

   1 /*
   2  * RNG driver for Intel 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 <alan@redhat.com>
  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/module.h>
  28 #include <linux/kernel.h>
  29 #include <linux/pci.h>
  30 #include <linux/hw_random.h>
  31 #include <asm/io.h>
  32
  33
  34 #define PFX     KBUILD_MODNAME ": "
  35
  36 /*
  37  * RNG registers
  38  */
  39 #define INTEL_RNG_HW_STATUS                     0
  40 #define         INTEL_RNG_PRESENT               0x40
  41 #define         INTEL_RNG_ENABLED               0x01
  42 #define INTEL_RNG_STATUS                        1
  43 #define         INTEL_RNG_DATA_PRESENT          0x01
  44 #define INTEL_RNG_DATA                          2
  45
  46 /*
  47  * Magic address at which Intel PCI bridges locate the RNG
  48  */
  49 #define INTEL_RNG_ADDR                          0xFFBC015F
  50 #define INTEL_RNG_ADDR_LEN                      3
  51
  52 /*
  53  * Data for PCI driver interface
  54  *
  55  * This data only exists for exporting the supported
  56  * PCI ids via MODULE_DEVICE_TABLE.  We do not actually
  57  * register a pci_driver, because someone else might one day
  58  * want to register another driver on the same PCI id.
  59  */
  60 static const struct pci_device_id pci_tbl[] = {
  61         { 0x8086, 0x2418, PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0, },
  62         { 0x8086, 0x2428, PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0, },
  63         { 0x8086, 0x2430, PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0, },
  64         { 0x8086, 0x2448, PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0, },
  65         { 0x8086, 0x244e, PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0, },
  66         { 0x8086, 0x245e, PCI_ANY_ID, PCI_ANY_ID, 0, 0, 0, },
  67         { 0, }, /* terminate list */
  68 };
  69 MODULE_DEVICE_TABLE(pci, pci_tbl);
  70
  71
  72 static inline u8 hwstatus_get(void __iomem *mem)
  73 {
  74         return readb(mem + INTEL_RNG_HW_STATUS);
  75 }
  76
  77 static inline u8 hwstatus_set(void __iomem *mem,
  78                               u8 hw_status)
  79 {
  80         writeb(hw_status, mem + INTEL_RNG_HW_STATUS);
  81         return hwstatus_get(mem);
  82 }
  83
  84 static int intel_rng_data_present(struct hwrng *rng)
  85 {
  86         void __iomem *mem = (void __iomem *)rng->priv;
  87
  88         return !!(readb(mem + INTEL_RNG_STATUS) & INTEL_RNG_DATA_PRESENT);
  89 }
  90
  91 static int intel_rng_data_read(struct hwrng *rng, u32 *data)
  92 {
  93         void __iomem *mem = (void __iomem *)rng->priv;
  94
  95         *data = readb(mem + INTEL_RNG_DATA);
  96
  97         return 1;
  98 }
  99
 100 static int intel_rng_init(struct hwrng *rng)
 101 {
 102         void __iomem *mem = (void __iomem *)rng->priv;
 103         u8 hw_status;
 104         int err = -EIO;
 105
 106         hw_status = hwstatus_get(mem);
 107         /* turn RNG h/w on, if it's off */
 108         if ((hw_status & INTEL_RNG_ENABLED) == 0)
 109                 hw_status = hwstatus_set(mem, hw_status | INTEL_RNG_ENABLED);
 110         if ((hw_status & INTEL_RNG_ENABLED) == 0) {
 111                 printk(KERN_ERR PFX "cannot enable RNG, aborting\n");
 112                 goto out;
 113         }
 114         err = 0;
 115 out:
 116         return err;
 117 }
 118
 119 static void intel_rng_cleanup(struct hwrng *rng)
 120 {
 121         void __iomem *mem = (void __iomem *)rng->priv;
 122         u8 hw_status;
 123
 124         hw_status = hwstatus_get(mem);
 125         if (hw_status & INTEL_RNG_ENABLED)
 126                 hwstatus_set(mem, hw_status & ~INTEL_RNG_ENABLED);
 127         else
 128                 printk(KERN_WARNING PFX "unusual: RNG already disabled\n");
 129 }
 130
 131
 132 static struct hwrng intel_rng = {
 133         .name           = "intel",
 134         .init           = intel_rng_init,
 135         .cleanup        = intel_rng_cleanup,
 136         .data_present   = intel_rng_data_present,
 137         .data_read      = intel_rng_data_read,
 138 };
 139
 140
 141 static int __init mod_init(void)
 142 {
 143         int err = -ENODEV;
 144         void __iomem *mem;
 145         u8 hw_status;
 146
 147         if (!pci_dev_present(pci_tbl))
 148                 goto out; /* Device not found. */
 149
 150         err = -ENOMEM;
 151         mem = ioremap(INTEL_RNG_ADDR, INTEL_RNG_ADDR_LEN);
 152         if (!mem)
 153                 goto out;
 154         intel_rng.priv = (unsigned long)mem;
 155
 156         /* Check for Intel 82802 */
 157         err = -ENODEV;
 158         hw_status = hwstatus_get(mem);
 159         if ((hw_status & INTEL_RNG_PRESENT) == 0)
 160                 goto err_unmap;
 161
 162         printk(KERN_INFO "Intel 82802 RNG detected\n");
 163         err = hwrng_register(&intel_rng);
 164         if (err) {
 165                 printk(KERN_ERR PFX "RNG registering failed (%d)\n",
 166                        err);
 167                 goto err_unmap;
 168         }
 169 out:
 170         return err;
 171
 172 err_unmap:
 173         iounmap(mem);
 174         goto out;
 175 }
 176
 177 static void __exit mod_exit(void)
 178 {
 179         void __iomem *mem = (void __iomem *)intel_rng.priv;
 180
 181         hwrng_unregister(&intel_rng);
 182         iounmap(mem);
 183 }
 184
 185 subsys_initcall(mod_init);
 186 module_exit(mod_exit);
 187
 188 MODULE_DESCRIPTION("H/W RNG driver for Intel chipsets");
 189 MODULE_LICENSE("GPL");