drivers/char/hw_random/ks-sa-rng.c

   1 /*
   2  * Random Number Generator driver for the Keystone SOC
   3  *
   4  * Copyright (C) 2016 Texas Instruments Incorporated - http://www.ti.com
   5  *
   6  * Authors:     Sandeep Nair
   7  *              Vitaly Andrianov
   8  *
   9  * This program is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU General Public License
  11  * version 2 as published by the Free Software Foundation.
  12  *
  13  * This program is distributed in the hope that it will be useful, but
  14  * WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * General Public License for more details.
  17  */
  18
  19 #include <linux/hw_random.h>
  20 #include <linux/kernel.h>
  21 #include <linux/module.h>
  22 #include <linux/io.h>
  23 #include <linux/platform_device.h>
  24 #include <linux/clk.h>
  25 #include <linux/pm_runtime.h>
  26 #include <linux/err.h>
  27 #include <linux/regmap.h>
  28 #include <linux/mfd/syscon.h>
  29 #include <linux/of.h>
  30 #include <linux/of_address.h>
  31 #include <linux/delay.h>
  32
  33 #define SA_CMD_STATUS_OFS                       0x8
  34
  35 /* TRNG enable control in SA System module*/
  36 #define SA_CMD_STATUS_REG_TRNG_ENABLE           BIT(3)
  37
  38 /* TRNG start control in TRNG module */
  39 #define TRNG_CNTL_REG_TRNG_ENABLE               BIT(10)
  40
  41 /* Data ready indicator in STATUS register */
  42 #define TRNG_STATUS_REG_READY                   BIT(0)
  43
  44 /* Data ready clear control in INTACK register */
  45 #define TRNG_INTACK_REG_READY                   BIT(0)
  46
  47 /*
  48  * Number of samples taken to gather entropy during startup.
  49  * If value is 0, the number of samples is 2^24 else
  50  * equals value times 2^8.
  51  */
  52 #define TRNG_DEF_STARTUP_CYCLES                 0
  53 #define TRNG_CNTL_REG_STARTUP_CYCLES_SHIFT      16
  54
  55 /*
  56  * Minimum number of samples taken to regenerate entropy
  57  * If value is 0, the number of samples is 2^24 else
  58  * equals value times 2^6.
  59  */
  60 #define TRNG_DEF_MIN_REFILL_CYCLES              1
  61 #define TRNG_CFG_REG_MIN_REFILL_CYCLES_SHIFT    0
  62
  63 /*
  64  * Maximum number of samples taken to regenerate entropy
  65  * If value is 0, the number of samples is 2^24 else
  66  * equals value times 2^8.
  67  */
  68 #define TRNG_DEF_MAX_REFILL_CYCLES              0
  69 #define TRNG_CFG_REG_MAX_REFILL_CYCLES_SHIFT    16
  70
  71 /* Number of CLK input cycles between samples */
  72 #define TRNG_DEF_CLK_DIV_CYCLES                 0
  73 #define TRNG_CFG_REG_SAMPLE_DIV_SHIFT           8
  74
  75 /* Maximum retries to get rng data */
  76 #define SA_MAX_RNG_DATA_RETRIES                 5
  77 /* Delay between retries (in usecs) */
  78 #define SA_RNG_DATA_RETRY_DELAY                 5
  79
  80 struct trng_regs {
  81         u32     output_l;
  82         u32     output_h;
  83         u32     status;
  84         u32     intmask;
  85         u32     intack;
  86         u32     control;
  87         u32     config;
  88 };
  89
  90 struct ks_sa_rng {
  91         struct device   *dev;
  92         struct hwrng    rng;
  93         struct clk      *clk;
  94         struct regmap   *regmap_cfg;
  95         struct trng_regs *reg_rng;
  96 };
  97
  98 static int ks_sa_rng_init(struct hwrng *rng)
  99 {
 100         u32 value;
 101         struct device *dev = (struct device *)rng->priv;
 102         struct ks_sa_rng *ks_sa_rng = dev_get_drvdata(dev);
 103
 104         /* Enable RNG module */
 105         regmap_write_bits(ks_sa_rng->regmap_cfg, SA_CMD_STATUS_OFS,
 106                           SA_CMD_STATUS_REG_TRNG_ENABLE,
 107                           SA_CMD_STATUS_REG_TRNG_ENABLE);
 108
 109         /* Configure RNG module */
 110         writel(0, &ks_sa_rng->reg_rng->control);
 111         value = TRNG_DEF_STARTUP_CYCLES << TRNG_CNTL_REG_STARTUP_CYCLES_SHIFT;
 112         writel(value, &ks_sa_rng->reg_rng->control);
 113
 114         value = (TRNG_DEF_MIN_REFILL_CYCLES <<
 115                  TRNG_CFG_REG_MIN_REFILL_CYCLES_SHIFT) |
 116                 (TRNG_DEF_MAX_REFILL_CYCLES <<
 117                  TRNG_CFG_REG_MAX_REFILL_CYCLES_SHIFT) |
 118                 (TRNG_DEF_CLK_DIV_CYCLES <<
 119                  TRNG_CFG_REG_SAMPLE_DIV_SHIFT);
 120
 121         writel(value, &ks_sa_rng->reg_rng->config);
 122
 123         /* Disable all interrupts from TRNG */
 124         writel(0, &ks_sa_rng->reg_rng->intmask);
 125
 126         /* Enable RNG */
 127         value = readl(&ks_sa_rng->reg_rng->control);
 128         value |= TRNG_CNTL_REG_TRNG_ENABLE;
 129         writel(value, &ks_sa_rng->reg_rng->control);
 130
 131         return 0;
 132 }
 133
 134 static void ks_sa_rng_cleanup(struct hwrng *rng)
 135 {
 136         struct device *dev = (struct device *)rng->priv;
 137         struct ks_sa_rng *ks_sa_rng = dev_get_drvdata(dev);
 138
 139         /* Disable RNG */
 140         writel(0, &ks_sa_rng->reg_rng->control);
 141         regmap_write_bits(ks_sa_rng->regmap_cfg, SA_CMD_STATUS_OFS,
 142                           SA_CMD_STATUS_REG_TRNG_ENABLE, 0);
 143 }
 144
 145 static int ks_sa_rng_data_read(struct hwrng *rng, u32 *data)
 146 {
 147         struct device *dev = (struct device *)rng->priv;
 148         struct ks_sa_rng *ks_sa_rng = dev_get_drvdata(dev);
 149
 150         /* Read random data */
 151         data[0] = readl(&ks_sa_rng->reg_rng->output_l);
 152         data[1] = readl(&ks_sa_rng->reg_rng->output_h);
 153
 154         writel(TRNG_INTACK_REG_READY, &ks_sa_rng->reg_rng->intack);
 155
 156         return sizeof(u32) * 2;
 157 }
 158
 159 static int ks_sa_rng_data_present(struct hwrng *rng, int wait)
 160 {
 161         struct device *dev = (struct device *)rng->priv;
 162         struct ks_sa_rng *ks_sa_rng = dev_get_drvdata(dev);
 163
 164         u32     ready;
 165         int     j;
 166
 167         for (j = 0; j < SA_MAX_RNG_DATA_RETRIES; j++) {
 168                 ready = readl(&ks_sa_rng->reg_rng->status);
 169                 ready &= TRNG_STATUS_REG_READY;
 170
 171                 if (ready || !wait)
 172                         break;
 173
 174                 udelay(SA_RNG_DATA_RETRY_DELAY);
 175         }
 176
 177         return ready;
 178 }
 179
 180 static int ks_sa_rng_probe(struct platform_device *pdev)
 181 {
 182         struct ks_sa_rng        *ks_sa_rng;
 183         struct device           *dev = &pdev->dev;
 184         int                     ret;
 185         struct resource         *mem;
 186
 187         ks_sa_rng = devm_kzalloc(dev, sizeof(*ks_sa_rng), GFP_KERNEL);
 188         if (!ks_sa_rng)
 189                 return -ENOMEM;
 190
 191         ks_sa_rng->dev = dev;
 192         ks_sa_rng->rng = (struct hwrng) {
 193                 .name = "ks_sa_hwrng",
 194                 .init = ks_sa_rng_init,
 195                 .data_read = ks_sa_rng_data_read,
 196                 .data_present = ks_sa_rng_data_present,
 197                 .cleanup = ks_sa_rng_cleanup,
 198         };
 199         ks_sa_rng->rng.priv = (unsigned long)dev;
 200
 201         mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 202         ks_sa_rng->reg_rng = devm_ioremap_resource(dev, mem);
 203         if (IS_ERR(ks_sa_rng->reg_rng))
 204                 return PTR_ERR(ks_sa_rng->reg_rng);
 205
 206         ks_sa_rng->regmap_cfg =
 207                 syscon_regmap_lookup_by_phandle(dev->of_node,
 208                                                 "ti,syscon-sa-cfg");
 209
 210         if (IS_ERR(ks_sa_rng->regmap_cfg)) {
 211                 dev_err(dev, "syscon_node_to_regmap failed\n");
 212                 return -EINVAL;
 213         }
 214
 215         pm_runtime_enable(dev);
 216         ret = pm_runtime_get_sync(dev);
 217         if (ret < 0) {
 218                 dev_err(dev, "Failed to enable SA power-domain\n");
 219                 pm_runtime_disable(dev);
 220                 return ret;
 221         }
 222
 223         platform_set_drvdata(pdev, ks_sa_rng);
 224
 225         return devm_hwrng_register(&pdev->dev, &ks_sa_rng->rng);
 226 }
 227
 228 static int ks_sa_rng_remove(struct platform_device *pdev)
 229 {
 230         pm_runtime_put_sync(&pdev->dev);
 231         pm_runtime_disable(&pdev->dev);
 232
 233         return 0;
 234 }
 235
 236 static const struct of_device_id ks_sa_rng_dt_match[] = {
 237         {
 238                 .compatible = "ti,keystone-rng",
 239         },
 240         { },
 241 };
 242 MODULE_DEVICE_TABLE(of, ks_sa_rng_dt_match);
 243
 244 static struct platform_driver ks_sa_rng_driver = {
 245         .driver         = {
 246                 .name   = "ks-sa-rng",
 247                 .of_match_table = ks_sa_rng_dt_match,
 248         },
 249         .probe          = ks_sa_rng_probe,
 250         .remove         = ks_sa_rng_remove,
 251 };
 252
 253 module_platform_driver(ks_sa_rng_driver);
 254
 255 MODULE_DESCRIPTION("Keystone NETCP SA H/W Random Number Generator driver");
 256 MODULE_AUTHOR("Vitaly Andrianov <vitalya@ti.com>");
 257 MODULE_LICENSE("GPL");