drivers/char/hw_random/npcm-rng.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 // Copyright (c) 2019 Nuvoton Technology corporation.
   3
   4 #include <linux/kernel.h>
   5 #include <linux/module.h>
   6 #include <linux/io.h>
   7 #include <linux/iopoll.h>
   8 #include <linux/init.h>
   9 #include <linux/random.h>
  10 #include <linux/err.h>
  11 #include <linux/platform_device.h>
  12 #include <linux/hw_random.h>
  13 #include <linux/delay.h>
  14 #include <linux/of_irq.h>
  15 #include <linux/pm_runtime.h>
  16
  17 #define NPCM_RNGCS_REG          0x00    /* Control and status register */
  18 #define NPCM_RNGD_REG           0x04    /* Data register */
  19 #define NPCM_RNGMODE_REG        0x08    /* Mode register */
  20
  21 #define NPCM_RNG_CLK_SET_25MHZ  GENMASK(4, 3) /* 20-25 MHz */
  22 #define NPCM_RNG_DATA_VALID     BIT(1)
  23 #define NPCM_RNG_ENABLE         BIT(0)
  24 #define NPCM_RNG_M1ROSEL        BIT(1)
  25
  26 #define NPCM_RNG_TIMEOUT_USEC   20000
  27 #define NPCM_RNG_POLL_USEC      1000
  28
  29 #define to_npcm_rng(p)  container_of(p, struct npcm_rng, rng)
  30
  31 struct npcm_rng {
  32         void __iomem *base;
  33         struct hwrng rng;
  34 };
  35
  36 static int npcm_rng_init(struct hwrng *rng)
  37 {
  38         struct npcm_rng *priv = to_npcm_rng(rng);
  39
  40         writel(NPCM_RNG_CLK_SET_25MHZ | NPCM_RNG_ENABLE,
  41                priv->base + NPCM_RNGCS_REG);
  42
  43         return 0;
  44 }
  45
  46 static void npcm_rng_cleanup(struct hwrng *rng)
  47 {
  48         struct npcm_rng *priv = to_npcm_rng(rng);
  49
  50         writel(NPCM_RNG_CLK_SET_25MHZ, priv->base + NPCM_RNGCS_REG);
  51 }
  52
  53 static int npcm_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
  54 {
  55         struct npcm_rng *priv = to_npcm_rng(rng);
  56         int retval = 0;
  57         int ready;
  58
  59         pm_runtime_get_sync((struct device *)priv->rng.priv);
  60
  61         while (max) {
  62                 if (wait) {
  63                         if (readb_poll_timeout(priv->base + NPCM_RNGCS_REG,
  64                                                ready,
  65                                                ready & NPCM_RNG_DATA_VALID,
  66                                                NPCM_RNG_POLL_USEC,
  67                                                NPCM_RNG_TIMEOUT_USEC))
  68                                 break;
  69                 } else {
  70                         if ((readb(priv->base + NPCM_RNGCS_REG) &
  71                             NPCM_RNG_DATA_VALID) == 0)
  72                                 break;
  73                 }
  74
  75                 *(u8 *)buf = readb(priv->base + NPCM_RNGD_REG);
  76                 retval++;
  77                 buf++;
  78                 max--;
  79         }
  80
  81         pm_runtime_mark_last_busy((struct device *)priv->rng.priv);
  82         pm_runtime_put_sync_autosuspend((struct device *)priv->rng.priv);
  83
  84         return retval || !wait ? retval : -EIO;
  85 }
  86
  87 static int npcm_rng_probe(struct platform_device *pdev)
  88 {
  89         struct npcm_rng *priv;
  90         int ret;
  91
  92         priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
  93         if (!priv)
  94                 return -ENOMEM;
  95
  96         priv->base = devm_platform_ioremap_resource(pdev, 0);
  97         if (IS_ERR(priv->base))
  98                 return PTR_ERR(priv->base);
  99
 100         dev_set_drvdata(&pdev->dev, priv);
 101         pm_runtime_set_autosuspend_delay(&pdev->dev, 100);
 102         pm_runtime_use_autosuspend(&pdev->dev);
 103         pm_runtime_enable(&pdev->dev);
 104
 105 #ifndef CONFIG_PM
 106         priv->rng.init = npcm_rng_init;
 107         priv->rng.cleanup = npcm_rng_cleanup;
 108 #endif
 109         priv->rng.name = pdev->name;
 110         priv->rng.read = npcm_rng_read;
 111         priv->rng.priv = (unsigned long)&pdev->dev;
 112         priv->rng.quality = 1000;
 113
 114         writel(NPCM_RNG_M1ROSEL, priv->base + NPCM_RNGMODE_REG);
 115
 116         ret = devm_hwrng_register(&pdev->dev, &priv->rng);
 117         if (ret) {
 118                 dev_err(&pdev->dev, "Failed to register rng device: %d\n",
 119                         ret);
 120                 pm_runtime_disable(&pdev->dev);
 121                 pm_runtime_set_suspended(&pdev->dev);
 122                 return ret;
 123         }
 124
 125         return 0;
 126 }
 127
 128 static int npcm_rng_remove(struct platform_device *pdev)
 129 {
 130         struct npcm_rng *priv = platform_get_drvdata(pdev);
 131
 132         devm_hwrng_unregister(&pdev->dev, &priv->rng);
 133         pm_runtime_disable(&pdev->dev);
 134         pm_runtime_set_suspended(&pdev->dev);
 135
 136         return 0;
 137 }
 138
 139 #ifdef CONFIG_PM
 140 static int npcm_rng_runtime_suspend(struct device *dev)
 141 {
 142         struct npcm_rng *priv = dev_get_drvdata(dev);
 143
 144         npcm_rng_cleanup(&priv->rng);
 145
 146         return 0;
 147 }
 148
 149 static int npcm_rng_runtime_resume(struct device *dev)
 150 {
 151         struct npcm_rng *priv = dev_get_drvdata(dev);
 152
 153         return npcm_rng_init(&priv->rng);
 154 }
 155 #endif
 156
 157 static const struct dev_pm_ops npcm_rng_pm_ops = {
 158         SET_RUNTIME_PM_OPS(npcm_rng_runtime_suspend,
 159                            npcm_rng_runtime_resume, NULL)
 160         SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
 161                                 pm_runtime_force_resume)
 162 };
 163
 164 static const struct of_device_id rng_dt_id[] __maybe_unused = {
 165         { .compatible = "nuvoton,npcm750-rng",  },
 166         {},
 167 };
 168 MODULE_DEVICE_TABLE(of, rng_dt_id);
 169
 170 static struct platform_driver npcm_rng_driver = {
 171         .driver = {
 172                 .name           = "npcm-rng",
 173                 .pm             = &npcm_rng_pm_ops,
 174                 .of_match_table = of_match_ptr(rng_dt_id),
 175         },
 176         .probe          = npcm_rng_probe,
 177         .remove         = npcm_rng_remove,
 178 };
 179
 180 module_platform_driver(npcm_rng_driver);
 181
 182 MODULE_DESCRIPTION("Nuvoton NPCM Random Number Generator Driver");
 183 MODULE_AUTHOR("Tomer Maimon <tomer.maimon@nuvoton.com>");
 184 MODULE_LICENSE("GPL v2");