drivers/char/hw_random/ppc4xx-rng.c

   1 /*
   2  * Generic PowerPC 44x RNG driver
   3  *
   4  * Copyright 2011 IBM Corporation
   5  *
   6  * This program is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License as published by the
   8  * Free Software Foundation; version 2 of the License.
   9  */
  10
  11 #include <linux/module.h>
  12 #include <linux/kernel.h>
  13 #include <linux/platform_device.h>
  14 #include <linux/hw_random.h>
  15 #include <linux/delay.h>
  16 #include <linux/of_platform.h>
  17 #include <asm/io.h>
  18
  19 #define PPC4XX_TRNG_DEV_CTRL 0x60080
  20
  21 #define PPC4XX_TRNGE 0x00020000
  22 #define PPC4XX_TRNG_CTRL 0x0008
  23 #define PPC4XX_TRNG_CTRL_DALM 0x20
  24 #define PPC4XX_TRNG_STAT 0x0004
  25 #define PPC4XX_TRNG_STAT_B 0x1
  26 #define PPC4XX_TRNG_DATA 0x0000
  27
  28 #define MODULE_NAME "ppc4xx_rng"
  29
  30 static int ppc4xx_rng_data_present(struct hwrng *rng, int wait)
  31 {
  32         void __iomem *rng_regs = (void __iomem *) rng->priv;
  33         int busy, i, present = 0;
  34
  35         for (i = 0; i < 20; i++) {
  36                 busy = (in_le32(rng_regs + PPC4XX_TRNG_STAT) & PPC4XX_TRNG_STAT_B);
  37                 if (!busy || !wait) {
  38                         present = 1;
  39                         break;
  40                 }
  41                 udelay(10);
  42         }
  43         return present;
  44 }
  45
  46 static int ppc4xx_rng_data_read(struct hwrng *rng, u32 *data)
  47 {
  48         void __iomem *rng_regs = (void __iomem *) rng->priv;
  49         *data = in_le32(rng_regs + PPC4XX_TRNG_DATA);
  50         return 4;
  51 }
  52
  53 static int ppc4xx_rng_enable(int enable)
  54 {
  55         struct device_node *ctrl;
  56         void __iomem *ctrl_reg;
  57         int err = 0;
  58         u32 val;
  59
  60         /* Find the main crypto device node and map it to turn the TRNG on */
  61         ctrl = of_find_compatible_node(NULL, NULL, "amcc,ppc4xx-crypto");
  62         if (!ctrl)
  63                 return -ENODEV;
  64
  65         ctrl_reg = of_iomap(ctrl, 0);
  66         if (!ctrl_reg) {
  67                 err = -ENODEV;
  68                 goto out;
  69         }
  70
  71         val = in_le32(ctrl_reg + PPC4XX_TRNG_DEV_CTRL);
  72
  73         if (enable)
  74                 val |= PPC4XX_TRNGE;
  75         else
  76                 val = val & ~PPC4XX_TRNGE;
  77
  78         out_le32(ctrl_reg + PPC4XX_TRNG_DEV_CTRL, val);
  79         iounmap(ctrl_reg);
  80
  81 out:
  82         of_node_put(ctrl);
  83
  84         return err;
  85 }
  86
  87 static struct hwrng ppc4xx_rng = {
  88         .name = MODULE_NAME,
  89         .data_present = ppc4xx_rng_data_present,
  90         .data_read = ppc4xx_rng_data_read,
  91 };
  92
  93 static int __devinit ppc4xx_rng_probe(struct platform_device *dev)
  94 {
  95         void __iomem *rng_regs;
  96         int err = 0;
  97
  98         rng_regs = of_iomap(dev->dev.of_node, 0);
  99         if (!rng_regs)
 100                 return -ENODEV;
 101
 102         err = ppc4xx_rng_enable(1);
 103         if (err)
 104                 return err;
 105
 106         out_le32(rng_regs + PPC4XX_TRNG_CTRL, PPC4XX_TRNG_CTRL_DALM);
 107         ppc4xx_rng.priv = (unsigned long) rng_regs;
 108
 109         err = hwrng_register(&ppc4xx_rng);
 110
 111         return err;
 112 }
 113
 114 static int __devexit ppc4xx_rng_remove(struct platform_device *dev)
 115 {
 116         void __iomem *rng_regs = (void __iomem *) ppc4xx_rng.priv;
 117
 118         hwrng_unregister(&ppc4xx_rng);
 119         ppc4xx_rng_enable(0);
 120         iounmap(rng_regs);
 121
 122         return 0;
 123 }
 124
 125 static struct of_device_id ppc4xx_rng_match[] = {
 126         { .compatible = "ppc4xx-rng", },
 127         { .compatible = "amcc,ppc460ex-rng", },
 128         { .compatible = "amcc,ppc440epx-rng", },
 129         {},
 130 };
 131
 132 static struct platform_driver ppc4xx_rng_driver = {
 133         .driver = {
 134                 .name = MODULE_NAME,
 135                 .owner = THIS_MODULE,
 136                 .of_match_table = ppc4xx_rng_match,
 137         },
 138         .probe = ppc4xx_rng_probe,
 139         .remove = ppc4xx_rng_remove,
 140 };
 141
 142 module_platform_driver(ppc4xx_rng_driver);
 143
 144 MODULE_LICENSE("GPL");
 145 MODULE_AUTHOR("Josh Boyer <jwboyer@linux.vnet.ibm.com>");
 146 MODULE_DESCRIPTION("HW RNG driver for PPC 4xx processors");