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/of.h>
  12 #include <linux/platform_device.h>
  13 #include <linux/hw_random.h>
  14 #include <linux/delay.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_62_5MHZ        BIT(2) /* 60-80 MHz */
  22 #define NPCM_RNG_CLK_SET_25MHZ  GENMASK(4, 3) /* 20-25 MHz */
  23 #define NPCM_RNG_DATA_VALID     BIT(1)
  24 #define NPCM_RNG_ENABLE         BIT(0)
  25 #define NPCM_RNG_M1ROSEL        BIT(1)
  26
  27 #define NPCM_RNG_TIMEOUT_USEC   20000
  28 #define NPCM_RNG_POLL_USEC      1000
  29
  30 #define to_npcm_rng(p)  container_of(p, struct npcm_rng, rng)
  31
  32 struct npcm_rng {
  33         void __iomem *base;
  34         struct hwrng rng;
  35         u32 clkp;
  36 };
  37
  38 static int npcm_rng_init(struct hwrng *rng)
  39 {
  40         struct npcm_rng *priv = to_npcm_rng(rng);
  41
  42         writel(priv->clkp | NPCM_RNG_ENABLE, priv->base + NPCM_RNGCS_REG);
  43
  44         return 0;
  45 }
  46
  47 static void npcm_rng_cleanup(struct hwrng *rng)
  48 {
  49         struct npcm_rng *priv = to_npcm_rng(rng);
  50
  51         writel(priv->clkp, priv->base + NPCM_RNGCS_REG);
  52 }
  53
  54 static int npcm_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
  55 {
  56         struct npcm_rng *priv = to_npcm_rng(rng);
  57         int retval = 0;
  58         int ready;
  59
  60         pm_runtime_get_sync((struct device *)priv->rng.priv);
  61
  62         while (max) {
  63                 if (wait) {
  64                         if (readb_poll_timeout(priv->base + NPCM_RNGCS_REG,
  65                                                ready,
  66                                                ready & NPCM_RNG_DATA_VALID,
  67                                                NPCM_RNG_POLL_USEC,
  68                                                NPCM_RNG_TIMEOUT_USEC))
  69                                 break;
  70                 } else {
  71                         if ((readb(priv->base + NPCM_RNGCS_REG) &
  72                             NPCM_RNG_DATA_VALID) == 0)
  73                                 break;
  74                 }
  75
  76                 *(u8 *)buf = readb(priv->base + NPCM_RNGD_REG);
  77                 retval++;
  78                 buf++;
  79                 max--;
  80         }
  81
  82         pm_runtime_mark_last_busy((struct device *)priv->rng.priv);
  83         pm_runtime_put_sync_autosuspend((struct device *)priv->rng.priv);
  84
  85         return retval || !wait ? retval : -EIO;
  86 }
  87
  88 static int npcm_rng_probe(struct platform_device *pdev)
  89 {
  90         struct npcm_rng *priv;
  91         int ret;
  92
  93         priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
  94         if (!priv)
  95                 return -ENOMEM;
  96
  97         priv->base = devm_platform_ioremap_resource(pdev, 0);
  98         if (IS_ERR(priv->base))
  99                 return PTR_ERR(priv->base);
 100
 101         dev_set_drvdata(&pdev->dev, priv);
 102         pm_runtime_set_autosuspend_delay(&pdev->dev, 100);
 103         pm_runtime_use_autosuspend(&pdev->dev);
 104         pm_runtime_enable(&pdev->dev);
 105
 106 #ifndef CONFIG_PM
 107         priv->rng.init = npcm_rng_init;
 108         priv->rng.cleanup = npcm_rng_cleanup;
 109 #endif
 110         priv->rng.name = pdev->name;
 111         priv->rng.read = npcm_rng_read;
 112         priv->rng.priv = (unsigned long)&pdev->dev;
 113         priv->clkp = (u32)(uintptr_t)of_device_get_match_data(&pdev->dev);
 114
 115         writel(NPCM_RNG_M1ROSEL, priv->base + NPCM_RNGMODE_REG);
 116
 117         ret = devm_hwrng_register(&pdev->dev, &priv->rng);
 118         if (ret) {
 119                 dev_err(&pdev->dev, "Failed to register rng device: %d\n",
 120                         ret);
 121                 pm_runtime_disable(&pdev->dev);
 122                 pm_runtime_set_suspended(&pdev->dev);
 123                 return ret;
 124         }
 125
 126         return 0;
 127 }
 128
 129 static void npcm_rng_remove(struct platform_device *pdev)
 130 {
 131         struct npcm_rng *priv = platform_get_drvdata(pdev);
 132
 133         devm_hwrng_unregister(&pdev->dev, &priv->rng);
 134         pm_runtime_disable(&pdev->dev);
 135         pm_runtime_set_suspended(&pdev->dev);
 136 }
 137
 138 #ifdef CONFIG_PM
 139 static int npcm_rng_runtime_suspend(struct device *dev)
 140 {
 141         struct npcm_rng *priv = dev_get_drvdata(dev);
 142
 143         npcm_rng_cleanup(&priv->rng);
 144
 145         return 0;
 146 }
 147
 148 static int npcm_rng_runtime_resume(struct device *dev)
 149 {
 150         struct npcm_rng *priv = dev_get_drvdata(dev);
 151
 152         return npcm_rng_init(&priv->rng);
 153 }
 154 #endif
 155
 156 static const struct dev_pm_ops npcm_rng_pm_ops = {
 157         SET_RUNTIME_PM_OPS(npcm_rng_runtime_suspend,
 158                            npcm_rng_runtime_resume, NULL)
 159         SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
 160                                 pm_runtime_force_resume)
 161 };
 162
 163 static const struct of_device_id rng_dt_id[] __maybe_unused = {
 164         { .compatible = "nuvoton,npcm750-rng",
 165                 .data = (void *)NPCM_RNG_CLK_SET_25MHZ },
 166         { .compatible = "nuvoton,npcm845-rng",
 167                 .data = (void *)NPCM_RNG_CLK_SET_62_5MHZ },
 168         {},
 169 };
 170 MODULE_DEVICE_TABLE(of, rng_dt_id);
 171
 172 static struct platform_driver npcm_rng_driver = {
 173         .driver = {
 174                 .name           = "npcm-rng",
 175                 .pm             = &npcm_rng_pm_ops,
 176                 .of_match_table = of_match_ptr(rng_dt_id),
 177         },
 178         .probe          = npcm_rng_probe,
 179         .remove         = npcm_rng_remove,
 180 };
 181
 182 module_platform_driver(npcm_rng_driver);
 183
 184 MODULE_DESCRIPTION("Nuvoton NPCM Random Number Generator Driver");
 185 MODULE_AUTHOR("Tomer Maimon <[email protected]>");
 186 MODULE_LICENSE("GPL v2");