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