drivers/char/hw_random/pasemi-rng.c

   1 /*
   2  * Copyright (C) 2006-2007 PA Semi, Inc
   3  *
   4  * Maintained by: Olof Johansson <olof@lixom.net>
   5  *
   6  * Driver for the PWRficient onchip rng
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
  20  */
  21
  22 #include <linux/module.h>
  23 #include <linux/kernel.h>
  24 #include <linux/platform_device.h>
  25 #include <linux/hw_random.h>
  26 #include <linux/delay.h>
  27 #include <linux/of_address.h>
  28 #include <linux/of_platform.h>
  29 #include <asm/io.h>
  30
  31 #define SDCRNG_CTL_REG                  0x00
  32 #define   SDCRNG_CTL_FVLD_M             0x0000f000
  33 #define   SDCRNG_CTL_FVLD_S             12
  34 #define   SDCRNG_CTL_KSZ                0x00000800
  35 #define   SDCRNG_CTL_RSRC_CRG           0x00000010
  36 #define   SDCRNG_CTL_RSRC_RRG           0x00000000
  37 #define   SDCRNG_CTL_CE                 0x00000004
  38 #define   SDCRNG_CTL_RE                 0x00000002
  39 #define   SDCRNG_CTL_DR                 0x00000001
  40 #define   SDCRNG_CTL_SELECT_RRG_RNG     (SDCRNG_CTL_RE | SDCRNG_CTL_RSRC_RRG)
  41 #define   SDCRNG_CTL_SELECT_CRG_RNG     (SDCRNG_CTL_CE | SDCRNG_CTL_RSRC_CRG)
  42 #define SDCRNG_VAL_REG                  0x20
  43
  44 #define MODULE_NAME "pasemi_rng"
  45
  46 static int pasemi_rng_data_present(struct hwrng *rng, int wait)
  47 {
  48         void __iomem *rng_regs = (void __iomem *)rng->priv;
  49         int data, i;
  50
  51         for (i = 0; i < 20; i++) {
  52                 data = (in_le32(rng_regs + SDCRNG_CTL_REG)
  53                         & SDCRNG_CTL_FVLD_M) ? 1 : 0;
  54                 if (data || !wait)
  55                         break;
  56                 udelay(10);
  57         }
  58         return data;
  59 }
  60
  61 static int pasemi_rng_data_read(struct hwrng *rng, u32 *data)
  62 {
  63         void __iomem *rng_regs = (void __iomem *)rng->priv;
  64         *data = in_le32(rng_regs + SDCRNG_VAL_REG);
  65         return 4;
  66 }
  67
  68 static int pasemi_rng_init(struct hwrng *rng)
  69 {
  70         void __iomem *rng_regs = (void __iomem *)rng->priv;
  71         u32 ctl;
  72
  73         ctl = SDCRNG_CTL_DR | SDCRNG_CTL_SELECT_RRG_RNG | SDCRNG_CTL_KSZ;
  74         out_le32(rng_regs + SDCRNG_CTL_REG, ctl);
  75         out_le32(rng_regs + SDCRNG_CTL_REG, ctl & ~SDCRNG_CTL_DR);
  76
  77         return 0;
  78 }
  79
  80 static void pasemi_rng_cleanup(struct hwrng *rng)
  81 {
  82         void __iomem *rng_regs = (void __iomem *)rng->priv;
  83         u32 ctl;
  84
  85         ctl = SDCRNG_CTL_RE | SDCRNG_CTL_CE;
  86         out_le32(rng_regs + SDCRNG_CTL_REG,
  87                  in_le32(rng_regs + SDCRNG_CTL_REG) & ~ctl);
  88 }
  89
  90 static struct hwrng pasemi_rng = {
  91         .name           = MODULE_NAME,
  92         .init           = pasemi_rng_init,
  93         .cleanup        = pasemi_rng_cleanup,
  94         .data_present   = pasemi_rng_data_present,
  95         .data_read      = pasemi_rng_data_read,
  96 };
  97
  98 static int rng_probe(struct platform_device *ofdev)
  99 {
 100         void __iomem *rng_regs;
 101         struct device_node *rng_np = ofdev->dev.of_node;
 102         struct resource res;
 103         int err = 0;
 104
 105         err = of_address_to_resource(rng_np, 0, &res);
 106         if (err)
 107                 return -ENODEV;
 108
 109         rng_regs = ioremap(res.start, 0x100);
 110
 111         if (!rng_regs)
 112                 return -ENOMEM;
 113
 114         pasemi_rng.priv = (unsigned long)rng_regs;
 115
 116         printk(KERN_INFO "Registering PA Semi RNG\n");
 117
 118         err = hwrng_register(&pasemi_rng);
 119
 120         if (err)
 121                 iounmap(rng_regs);
 122
 123         return err;
 124 }
 125
 126 static int rng_remove(struct platform_device *dev)
 127 {
 128         void __iomem *rng_regs = (void __iomem *)pasemi_rng.priv;
 129
 130         hwrng_unregister(&pasemi_rng);
 131         iounmap(rng_regs);
 132
 133         return 0;
 134 }
 135
 136 static struct of_device_id rng_match[] = {
 137         { .compatible      = "1682m-rng", },
 138         { .compatible      = "pasemi,pwrficient-rng", },
 139         { },
 140 };
 141
 142 static struct platform_driver rng_driver = {
 143         .driver = {
 144                 .name = "pasemi-rng",
 145                 .owner = THIS_MODULE,
 146                 .of_match_table = rng_match,
 147         },
 148         .probe          = rng_probe,
 149         .remove         = rng_remove,
 150 };
 151
 152 module_platform_driver(rng_driver);
 153
 154 MODULE_LICENSE("GPL");
 155 MODULE_AUTHOR("Egor Martovetsky <egor@pasemi.com>");
 156 MODULE_DESCRIPTION("H/W RNG driver for PA Semi processor");