drivers/char/hw_random/pasemi-rng.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2006-2007 PA Semi, Inc
   4  *
   5  * Maintained by: Olof Johansson <olof@lixom.net>
   6  *
   7  * Driver for the PWRficient onchip rng
   8  */
   9
  10 #include <linux/module.h>
  11 #include <linux/kernel.h>
  12 #include <linux/platform_device.h>
  13 #include <linux/hw_random.h>
  14 #include <linux/delay.h>
  15 #include <linux/of_address.h>
  16 #include <linux/of_platform.h>
  17 #include <linux/io.h>
  18
  19 #define SDCRNG_CTL_REG                  0x00
  20 #define   SDCRNG_CTL_FVLD_M             0x0000f000
  21 #define   SDCRNG_CTL_FVLD_S             12
  22 #define   SDCRNG_CTL_KSZ                0x00000800
  23 #define   SDCRNG_CTL_RSRC_CRG           0x00000010
  24 #define   SDCRNG_CTL_RSRC_RRG           0x00000000
  25 #define   SDCRNG_CTL_CE                 0x00000004
  26 #define   SDCRNG_CTL_RE                 0x00000002
  27 #define   SDCRNG_CTL_DR                 0x00000001
  28 #define   SDCRNG_CTL_SELECT_RRG_RNG     (SDCRNG_CTL_RE | SDCRNG_CTL_RSRC_RRG)
  29 #define   SDCRNG_CTL_SELECT_CRG_RNG     (SDCRNG_CTL_CE | SDCRNG_CTL_RSRC_CRG)
  30 #define SDCRNG_VAL_REG                  0x20
  31
  32 #define MODULE_NAME "pasemi_rng"
  33
  34 static int pasemi_rng_data_present(struct hwrng *rng, int wait)
  35 {
  36         void __iomem *rng_regs = (void __iomem *)rng->priv;
  37         int data, i;
  38
  39         for (i = 0; i < 20; i++) {
  40                 data = (in_le32(rng_regs + SDCRNG_CTL_REG)
  41                         & SDCRNG_CTL_FVLD_M) ? 1 : 0;
  42                 if (data || !wait)
  43                         break;
  44                 udelay(10);
  45         }
  46         return data;
  47 }
  48
  49 static int pasemi_rng_data_read(struct hwrng *rng, u32 *data)
  50 {
  51         void __iomem *rng_regs = (void __iomem *)rng->priv;
  52         *data = in_le32(rng_regs + SDCRNG_VAL_REG);
  53         return 4;
  54 }
  55
  56 static int pasemi_rng_init(struct hwrng *rng)
  57 {
  58         void __iomem *rng_regs = (void __iomem *)rng->priv;
  59         u32 ctl;
  60
  61         ctl = SDCRNG_CTL_DR | SDCRNG_CTL_SELECT_RRG_RNG | SDCRNG_CTL_KSZ;
  62         out_le32(rng_regs + SDCRNG_CTL_REG, ctl);
  63         out_le32(rng_regs + SDCRNG_CTL_REG, ctl & ~SDCRNG_CTL_DR);
  64
  65         return 0;
  66 }
  67
  68 static void pasemi_rng_cleanup(struct hwrng *rng)
  69 {
  70         void __iomem *rng_regs = (void __iomem *)rng->priv;
  71         u32 ctl;
  72
  73         ctl = SDCRNG_CTL_RE | SDCRNG_CTL_CE;
  74         out_le32(rng_regs + SDCRNG_CTL_REG,
  75                  in_le32(rng_regs + SDCRNG_CTL_REG) & ~ctl);
  76 }
  77
  78 static struct hwrng pasemi_rng = {
  79         .name           = MODULE_NAME,
  80         .init           = pasemi_rng_init,
  81         .cleanup        = pasemi_rng_cleanup,
  82         .data_present   = pasemi_rng_data_present,
  83         .data_read      = pasemi_rng_data_read,
  84 };
  85
  86 static int rng_probe(struct platform_device *pdev)
  87 {
  88         void __iomem *rng_regs;
  89
  90         rng_regs = devm_platform_ioremap_resource(pdev, 0);
  91         if (IS_ERR(rng_regs))
  92                 return PTR_ERR(rng_regs);
  93
  94         pasemi_rng.priv = (unsigned long)rng_regs;
  95
  96         pr_info("Registering PA Semi RNG\n");
  97         return devm_hwrng_register(&pdev->dev, &pasemi_rng);
  98 }
  99
 100 static const struct of_device_id rng_match[] = {
 101         { .compatible      = "1682m-rng", },
 102         { .compatible      = "pasemi,pwrficient-rng", },
 103         { },
 104 };
 105 MODULE_DEVICE_TABLE(of, rng_match);
 106
 107 static struct platform_driver rng_driver = {
 108         .driver = {
 109                 .name = "pasemi-rng",
 110                 .of_match_table = rng_match,
 111         },
 112         .probe          = rng_probe,
 113 };
 114
 115 module_platform_driver(rng_driver);
 116
 117 MODULE_LICENSE("GPL");
 118 MODULE_AUTHOR("Egor Martovetsky <egor@pasemi.com>");
 119 MODULE_DESCRIPTION("H/W RNG driver for PA Semi processor");