hwrng: npcm - add NPCM RNG driver

Add Nuvoton NPCM BMC Random Number Generator(RNG) driver.
Signed-off-by: Tomer Maimon <tmaimon77@gmail.com>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/char/hw_random/Kconfig

@@ -440,6 +440,19 @@ config HW_RANDOM_OPTEE
 
 	  If unsure, say Y.
 
+config HW_RANDOM_NPCM
+	tristate "NPCM Random Number Generator support"
+	depends on ARCH_NPCM || COMPILE_TEST
+	default HW_RANDOM
+	help
+ 	  This driver provides support for the Random Number
+	  Generator hardware available in Nuvoton NPCM SoCs.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called npcm-rng.
+
+ 	  If unsure, say Y.
+
 endif # HW_RANDOM
 
 config UML_RANDOM

drivers/char/hw_random/Makefile

@@ -39,3 +39,4 @@ obj-$(CONFIG_HW_RANDOM_MTK)	+= mtk-rng.o
 obj-$(CONFIG_HW_RANDOM_S390) += s390-trng.o
 obj-$(CONFIG_HW_RANDOM_KEYSTONE) += ks-sa-rng.o
 obj-$(CONFIG_HW_RANDOM_OPTEE) += optee-rng.o
+obj-$(CONFIG_HW_RANDOM_NPCM) += npcm-rng.o

drivers/char/hw_random/npcm-rng.c

+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2019 Nuvoton Technology corporation.
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/io.h>
+#include <linux/iopoll.h>
+#include <linux/init.h>
+#include <linux/random.h>
+#include <linux/err.h>
+#include <linux/platform_device.h>
+#include <linux/hw_random.h>
+#include <linux/delay.h>
+#include <linux/of_irq.h>
+#include <linux/pm_runtime.h>
+
+#define NPCM_RNGCS_REG		0x00	/* Control and status register */
+#define NPCM_RNGD_REG		0x04	/* Data register */
+#define NPCM_RNGMODE_REG	0x08	/* Mode register */
+
+#define NPCM_RNG_CLK_SET_25MHZ	GENMASK(4, 3) /* 20-25 MHz */
+#define NPCM_RNG_DATA_VALID	BIT(1)
+#define NPCM_RNG_ENABLE		BIT(0)
+#define NPCM_RNG_M1ROSEL	BIT(1)
+
+#define NPCM_RNG_TIMEOUT_USEC	20000
+#define NPCM_RNG_POLL_USEC	1000
+
+#define to_npcm_rng(p)	container_of(p, struct npcm_rng, rng)
+
+struct npcm_rng {
+	void __iomem *base;
+	struct hwrng rng;
+};
+
+static int npcm_rng_init(struct hwrng *rng)
+{
+	struct npcm_rng *priv = to_npcm_rng(rng);
+
+	writel(NPCM_RNG_CLK_SET_25MHZ | NPCM_RNG_ENABLE,
+	       priv->base + NPCM_RNGCS_REG);
+
+	return 0;
+}
+
+static void npcm_rng_cleanup(struct hwrng *rng)
+{
+	struct npcm_rng *priv = to_npcm_rng(rng);
+
+	writel(NPCM_RNG_CLK_SET_25MHZ, priv->base + NPCM_RNGCS_REG);
+}
+
+static int npcm_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
+{
+	struct npcm_rng *priv = to_npcm_rng(rng);
+	int retval = 0;
+	int ready;
+
+	pm_runtime_get_sync((struct device *)priv->rng.priv);
+
+	while (max >= sizeof(u32)) {
+		if (wait) {
+			if (readl_poll_timeout(priv->base + NPCM_RNGCS_REG,
+					       ready,
+					       ready & NPCM_RNG_DATA_VALID,
+					       NPCM_RNG_POLL_USEC,
+					       NPCM_RNG_TIMEOUT_USEC))
+				break;
+		} else {
+			if ((readl(priv->base + NPCM_RNGCS_REG) &
+			    NPCM_RNG_DATA_VALID) == 0)
+				break;
+		}
+
+		*(u32 *)buf = readl(priv->base + NPCM_RNGD_REG);
+		retval += sizeof(u32);
+		buf += sizeof(u32);
+		max -= sizeof(u32);
+	}
+
+	pm_runtime_mark_last_busy((struct device *)priv->rng.priv);
+	pm_runtime_put_sync_autosuspend((struct device *)priv->rng.priv);
+
+	return retval || !wait ? retval : -EIO;
+}
+
+static int npcm_rng_probe(struct platform_device *pdev)
+{
+	struct npcm_rng *priv;
+	struct resource *res;
+	int ret;
+
+	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	priv->base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(priv->base))
+		return PTR_ERR(priv->base);
+
+	dev_set_drvdata(&pdev->dev, priv);
+	pm_runtime_set_autosuspend_delay(&pdev->dev, 100);
+	pm_runtime_use_autosuspend(&pdev->dev);
+	pm_runtime_enable(&pdev->dev);
+
+#ifndef CONFIG_PM
+	priv->rng.init = npcm_rng_init;
+	priv->rng.cleanup = npcm_rng_cleanup;
+#endif
+	priv->rng.name = pdev->name;
+	priv->rng.read = npcm_rng_read;
+	priv->rng.priv = (unsigned long)&pdev->dev;
+	priv->rng.quality = 1000;
+
+	writel(NPCM_RNG_M1ROSEL, priv->base + NPCM_RNGMODE_REG);
+
+	ret = devm_hwrng_register(&pdev->dev, &priv->rng);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed to register rng device: %d\n",
+			ret);
+		pm_runtime_disable(&pdev->dev);
+		pm_runtime_set_suspended(&pdev->dev);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int npcm_rng_remove(struct platform_device *pdev)
+{
+	struct npcm_rng *priv = platform_get_drvdata(pdev);
+
+	devm_hwrng_unregister(&pdev->dev, &priv->rng);
+	pm_runtime_disable(&pdev->dev);
+	pm_runtime_set_suspended(&pdev->dev);
+
+	return 0;
+}
+
+#ifdef CONFIG_PM
+static int npcm_rng_runtime_suspend(struct device *dev)
+{
+	struct npcm_rng *priv = dev_get_drvdata(dev);
+
+	npcm_rng_cleanup(&priv->rng);
+
+	return 0;
+}
+
+static int npcm_rng_runtime_resume(struct device *dev)
+{
+	struct npcm_rng *priv = dev_get_drvdata(dev);
+
+	return npcm_rng_init(&priv->rng);
+}
+#endif
+
+static const struct dev_pm_ops npcm_rng_pm_ops = {
+	SET_RUNTIME_PM_OPS(npcm_rng_runtime_suspend,
+			   npcm_rng_runtime_resume, NULL)
+	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend,
+				pm_runtime_force_resume)
+};
+
+static const struct of_device_id rng_dt_id[] = {
+	{ .compatible = "nuvoton,npcm750-rng",  },
+	{},
+};
+MODULE_DEVICE_TABLE(of, rng_dt_id);
+
+static struct platform_driver npcm_rng_driver = {
+	.driver = {
+		.name		= "npcm-rng",
+		.pm		= &npcm_rng_pm_ops,
+		.of_match_table = of_match_ptr(rng_dt_id),
+	},
+	.probe		= npcm_rng_probe,
+	.remove		= npcm_rng_remove,
+};
+
+module_platform_driver(npcm_rng_driver);
+
+MODULE_DESCRIPTION("Nuvoton NPCM Random Number Generator Driver");
+MODULE_AUTHOR("Tomer Maimon <tomer.maimon@nuvoton.com>");
+MODULE_LICENSE("GPL v2");