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 #define GEODE_RNG_DATA_REG   0x50
  35 #define GEODE_RNG_STATUS_REG 0x54
  36
  37 /*
  38  * Data for PCI driver interface
  39  *
  40  * This data only exists for exporting the supported
  41  * PCI ids via MODULE_DEVICE_TABLE.  We do not actually
  42  * register a pci_driver, because someone else might one day
  43  * want to register another driver on the same PCI id.
  44  */
  45 static const struct pci_device_id pci_tbl[] = {
  46         { PCI_VDEVICE(AMD, PCI_DEVICE_ID_AMD_LX_AES), 0, },
  47         { 0, }, /* terminate list */
  48 };
  49 MODULE_DEVICE_TABLE(pci, pci_tbl);
  50
  51
  52 static int geode_rng_data_read(struct hwrng *rng, u32 *data)
  53 {
  54         void __iomem *mem = (void __iomem *)rng->priv;
  55
  56         *data = readl(mem + GEODE_RNG_DATA_REG);
  57
  58         return 4;
  59 }
  60
  61 static int geode_rng_data_present(struct hwrng *rng, int wait)
  62 {
  63         void __iomem *mem = (void __iomem *)rng->priv;
  64         int data, i;
  65
  66         for (i = 0; i < 20; i++) {
  67                 data = !!(readl(mem + GEODE_RNG_STATUS_REG));
  68                 if (data || !wait)
  69                         break;
  70                 udelay(10);
  71         }
  72         return data;
  73 }
  74
  75
  76 static struct hwrng geode_rng = {
  77         .name           = "geode",
  78         .data_present   = geode_rng_data_present,
  79         .data_read      = geode_rng_data_read,
  80 };
  81
  82
  83 static int __init mod_init(void)
  84 {
  85         struct pci_dev *pdev = NULL;
  86         const struct pci_device_id *ent;
  87         void __iomem *mem;
  88         unsigned long rng_base;
  89
  90         for_each_pci_dev(pdev) {
  91                 ent = pci_match_id(pci_tbl, pdev);
  92                 if (ent) {
  93                         rng_base = pci_resource_start(pdev, 0);
  94                         if (rng_base == 0)
  95                                 return -ENODEV;
  96
  97                         mem = devm_ioremap(&pdev->dev, rng_base, 0x58);
  98                         if (!mem)
  99                                 return -ENOMEM;
 100                         geode_rng.priv = (unsigned long)mem;
 101
 102                         pr_info("AMD Geode RNG detected\n");
 103                         return devm_hwrng_register(&pdev->dev, &geode_rng);
 104                 }
 105         }
 106
 107         /* Device not found. */
 108         return -ENODEV;
 109 }
 110
 111 static void __exit mod_exit(void)
 112 {
 113 }
 114
 115 module_init(mod_init);
 116 module_exit(mod_exit);
 117
 118 MODULE_DESCRIPTION("H/W RNG driver for AMD Geode LX CPUs");
 119 MODULE_LICENSE("GPL");