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

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Random Number Generator driver for the Keystone SOC
   4  *
   5  * Copyright (C) 2016 Texas Instruments Incorporated - https://www.ti.com
   6  *
   7  * Authors:     Sandeep Nair
   8  *              Vitaly Andrianov
   9  */
  10
  11 #include <linux/hw_random.h>
  12 #include <linux/kernel.h>
  13 #include <linux/module.h>
  14 #include <linux/io.h>
  15 #include <linux/platform_device.h>
  16 #include <linux/clk.h>
  17 #include <linux/pm_runtime.h>
  18 #include <linux/err.h>
  19 #include <linux/regmap.h>
  20 #include <linux/mfd/syscon.h>
  21 #include <linux/of.h>
  22 #include <linux/of_address.h>
  23 #include <linux/delay.h>
  24 #include <linux/timekeeping.h>
  25
  26 #define SA_CMD_STATUS_OFS                       0x8
  27
  28 /* TRNG enable control in SA System module*/
  29 #define SA_CMD_STATUS_REG_TRNG_ENABLE           BIT(3)
  30
  31 /* TRNG start control in TRNG module */
  32 #define TRNG_CNTL_REG_TRNG_ENABLE               BIT(10)
  33
  34 /* Data ready indicator in STATUS register */
  35 #define TRNG_STATUS_REG_READY                   BIT(0)
  36
  37 /* Data ready clear control in INTACK register */
  38 #define TRNG_INTACK_REG_READY                   BIT(0)
  39
  40 /*
  41  * Number of samples taken to gather entropy during startup.
  42  * If value is 0, the number of samples is 2^24 else
  43  * equals value times 2^8.
  44  */
  45 #define TRNG_DEF_STARTUP_CYCLES                 0
  46 #define TRNG_CNTL_REG_STARTUP_CYCLES_SHIFT      16
  47
  48 /*
  49  * Minimum number of samples taken to regenerate entropy
  50  * If value is 0, the number of samples is 2^24 else
  51  * equals value times 2^6.
  52  */
  53 #define TRNG_DEF_MIN_REFILL_CYCLES              1
  54 #define TRNG_CFG_REG_MIN_REFILL_CYCLES_SHIFT    0
  55
  56 /*
  57  * Maximum number of samples taken to regenerate entropy
  58  * If value is 0, the number of samples is 2^24 else
  59  * equals value times 2^8.
  60  */
  61 #define TRNG_DEF_MAX_REFILL_CYCLES              0
  62 #define TRNG_CFG_REG_MAX_REFILL_CYCLES_SHIFT    16
  63
  64 /* Number of CLK input cycles between samples */
  65 #define TRNG_DEF_CLK_DIV_CYCLES                 0
  66 #define TRNG_CFG_REG_SAMPLE_DIV_SHIFT           8
  67
  68 /* Maximum retries to get rng data */
  69 #define SA_MAX_RNG_DATA_RETRIES                 5
  70 /* Delay between retries (in usecs) */
  71 #define SA_RNG_DATA_RETRY_DELAY                 5
  72
  73 struct trng_regs {
  74         u32     output_l;
  75         u32     output_h;
  76         u32     status;
  77         u32     intmask;
  78         u32     intack;
  79         u32     control;
  80         u32     config;
  81 };
  82
  83 struct ks_sa_rng {
  84         struct device   *dev;
  85         struct hwrng    rng;
  86         struct clk      *clk;
  87         struct regmap   *regmap_cfg;
  88         struct trng_regs __iomem *reg_rng;
  89         u64 ready_ts;
  90         unsigned int refill_delay_ns;
  91 };
  92
  93 static unsigned int cycles_to_ns(unsigned long clk_rate, unsigned int cycles)
  94 {
  95         return DIV_ROUND_UP_ULL((TRNG_DEF_CLK_DIV_CYCLES + 1) * 1000000000ull *
  96                                 cycles, clk_rate);
  97 }
  98
  99 static unsigned int startup_delay_ns(unsigned long clk_rate)
 100 {
 101         if (!TRNG_DEF_STARTUP_CYCLES)
 102                 return cycles_to_ns(clk_rate, BIT(24));
 103         return cycles_to_ns(clk_rate, 256 * TRNG_DEF_STARTUP_CYCLES);
 104 }
 105
 106 static unsigned int refill_delay_ns(unsigned long clk_rate)
 107 {
 108         if (!TRNG_DEF_MAX_REFILL_CYCLES)
 109                 return cycles_to_ns(clk_rate, BIT(24));
 110         return cycles_to_ns(clk_rate, 256 * TRNG_DEF_MAX_REFILL_CYCLES);
 111 }
 112
 113 static int ks_sa_rng_init(struct hwrng *rng)
 114 {
 115         u32 value;
 116         struct device *dev = (struct device *)rng->priv;
 117         struct ks_sa_rng *ks_sa_rng = dev_get_drvdata(dev);
 118         unsigned long clk_rate = clk_get_rate(ks_sa_rng->clk);
 119
 120         /* Enable RNG module */
 121         regmap_write_bits(ks_sa_rng->regmap_cfg, SA_CMD_STATUS_OFS,
 122                           SA_CMD_STATUS_REG_TRNG_ENABLE,
 123                           SA_CMD_STATUS_REG_TRNG_ENABLE);
 124
 125         /* Configure RNG module */
 126         writel(0, &ks_sa_rng->reg_rng->control);
 127         value = TRNG_DEF_STARTUP_CYCLES << TRNG_CNTL_REG_STARTUP_CYCLES_SHIFT;
 128         writel(value, &ks_sa_rng->reg_rng->control);
 129
 130         value = (TRNG_DEF_MIN_REFILL_CYCLES <<
 131                  TRNG_CFG_REG_MIN_REFILL_CYCLES_SHIFT) |
 132                 (TRNG_DEF_MAX_REFILL_CYCLES <<
 133                  TRNG_CFG_REG_MAX_REFILL_CYCLES_SHIFT) |
 134                 (TRNG_DEF_CLK_DIV_CYCLES <<
 135                  TRNG_CFG_REG_SAMPLE_DIV_SHIFT);
 136
 137         writel(value, &ks_sa_rng->reg_rng->config);
 138
 139         /* Disable all interrupts from TRNG */
 140         writel(0, &ks_sa_rng->reg_rng->intmask);
 141
 142         /* Enable RNG */
 143         value = readl(&ks_sa_rng->reg_rng->control);
 144         value |= TRNG_CNTL_REG_TRNG_ENABLE;
 145         writel(value, &ks_sa_rng->reg_rng->control);
 146
 147         ks_sa_rng->refill_delay_ns = refill_delay_ns(clk_rate);
 148         ks_sa_rng->ready_ts = ktime_get_ns() +
 149                               startup_delay_ns(clk_rate);
 150
 151         return 0;
 152 }
 153
 154 static void ks_sa_rng_cleanup(struct hwrng *rng)
 155 {
 156         struct device *dev = (struct device *)rng->priv;
 157         struct ks_sa_rng *ks_sa_rng = dev_get_drvdata(dev);
 158
 159         /* Disable RNG */
 160         writel(0, &ks_sa_rng->reg_rng->control);
 161         regmap_write_bits(ks_sa_rng->regmap_cfg, SA_CMD_STATUS_OFS,
 162                           SA_CMD_STATUS_REG_TRNG_ENABLE, 0);
 163 }
 164
 165 static int ks_sa_rng_data_read(struct hwrng *rng, u32 *data)
 166 {
 167         struct device *dev = (struct device *)rng->priv;
 168         struct ks_sa_rng *ks_sa_rng = dev_get_drvdata(dev);
 169
 170         /* Read random data */
 171         data[0] = readl(&ks_sa_rng->reg_rng->output_l);
 172         data[1] = readl(&ks_sa_rng->reg_rng->output_h);
 173
 174         writel(TRNG_INTACK_REG_READY, &ks_sa_rng->reg_rng->intack);
 175         ks_sa_rng->ready_ts = ktime_get_ns() + ks_sa_rng->refill_delay_ns;
 176
 177         return sizeof(u32) * 2;
 178 }
 179
 180 static int ks_sa_rng_data_present(struct hwrng *rng, int wait)
 181 {
 182         struct device *dev = (struct device *)rng->priv;
 183         struct ks_sa_rng *ks_sa_rng = dev_get_drvdata(dev);
 184         u64 now = ktime_get_ns();
 185
 186         u32     ready;
 187         int     j;
 188
 189         if (wait && now < ks_sa_rng->ready_ts) {
 190                 /* Max delay expected here is 81920000 ns */
 191                 unsigned long min_delay =
 192                         DIV_ROUND_UP((u32)(ks_sa_rng->ready_ts - now), 1000);
 193
 194                 usleep_range(min_delay, min_delay + SA_RNG_DATA_RETRY_DELAY);
 195         }
 196
 197         for (j = 0; j < SA_MAX_RNG_DATA_RETRIES; j++) {
 198                 ready = readl(&ks_sa_rng->reg_rng->status);
 199                 ready &= TRNG_STATUS_REG_READY;
 200
 201                 if (ready || !wait)
 202                         break;
 203
 204                 udelay(SA_RNG_DATA_RETRY_DELAY);
 205         }
 206
 207         return ready;
 208 }
 209
 210 static int ks_sa_rng_probe(struct platform_device *pdev)
 211 {
 212         struct ks_sa_rng        *ks_sa_rng;
 213         struct device           *dev = &pdev->dev;
 214         int                     ret;
 215
 216         ks_sa_rng = devm_kzalloc(dev, sizeof(*ks_sa_rng), GFP_KERNEL);
 217         if (!ks_sa_rng)
 218                 return -ENOMEM;
 219
 220         ks_sa_rng->dev = dev;
 221         ks_sa_rng->rng = (struct hwrng) {
 222                 .name = "ks_sa_hwrng",
 223                 .init = ks_sa_rng_init,
 224                 .data_read = ks_sa_rng_data_read,
 225                 .data_present = ks_sa_rng_data_present,
 226                 .cleanup = ks_sa_rng_cleanup,
 227         };
 228         ks_sa_rng->rng.priv = (unsigned long)dev;
 229
 230         ks_sa_rng->reg_rng = devm_platform_ioremap_resource(pdev, 0);
 231         if (IS_ERR(ks_sa_rng->reg_rng))
 232                 return PTR_ERR(ks_sa_rng->reg_rng);
 233
 234         ks_sa_rng->regmap_cfg =
 235                 syscon_regmap_lookup_by_phandle(dev->of_node,
 236                                                 "ti,syscon-sa-cfg");
 237
 238         if (IS_ERR(ks_sa_rng->regmap_cfg)) {
 239                 dev_err(dev, "syscon_node_to_regmap failed\n");
 240                 return -EINVAL;
 241         }
 242
 243         pm_runtime_enable(dev);
 244         ret = pm_runtime_get_sync(dev);
 245         if (ret < 0) {
 246                 dev_err(dev, "Failed to enable SA power-domain\n");
 247                 pm_runtime_put_noidle(dev);
 248                 pm_runtime_disable(dev);
 249                 return ret;
 250         }
 251
 252         platform_set_drvdata(pdev, ks_sa_rng);
 253
 254         return devm_hwrng_register(&pdev->dev, &ks_sa_rng->rng);
 255 }
 256
 257 static int ks_sa_rng_remove(struct platform_device *pdev)
 258 {
 259         pm_runtime_put_sync(&pdev->dev);
 260         pm_runtime_disable(&pdev->dev);
 261
 262         return 0;
 263 }
 264
 265 static const struct of_device_id ks_sa_rng_dt_match[] = {
 266         {
 267                 .compatible = "ti,keystone-rng",
 268         },
 269         { },
 270 };
 271 MODULE_DEVICE_TABLE(of, ks_sa_rng_dt_match);
 272
 273 static struct platform_driver ks_sa_rng_driver = {
 274         .driver         = {
 275                 .name   = "ks-sa-rng",
 276                 .of_match_table = ks_sa_rng_dt_match,
 277         },
 278         .probe          = ks_sa_rng_probe,
 279         .remove         = ks_sa_rng_remove,
 280 };
 281
 282 module_platform_driver(ks_sa_rng_driver);
 283
 284 MODULE_DESCRIPTION("Keystone NETCP SA H/W Random Number Generator driver");
 285 MODULE_AUTHOR("Vitaly Andrianov <vitalya@ti.com>");
 286 MODULE_LICENSE("GPL");