[PATCH v2 2/2] hwrng: mtk: Add driver for hardware random generator on MT7623 SoC

[sean.wang at mediatek.com]

From: Sean Wang <sean.wang at mediatek.com>

This patch adds support for hardware random generator on MT7623 SoC
and should also work on other similar Mediatek SoCs. Currently,
the driver is already tested successfully with rng-tools.

Signed-off-by: Sean Wang <sean.wang at mediatek.com>
Reviewed-by: PrasannaKumar Muralidharan <prasannatsmkumar at gmail.com>
---
 drivers/char/hw_random/Kconfig   |  14 ++++
 drivers/char/hw_random/Makefile  |   1 +
 drivers/char/hw_random/mtk-rng.c | 168 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 183 insertions(+)
 create mode 100644 drivers/char/hw_random/mtk-rng.c

diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
index 0cafe08..df5e7c2 100644
--- a/drivers/char/hw_random/Kconfig
+++ b/drivers/char/hw_random/Kconfig
@@ -423,6 +423,20 @@ config HW_RANDOM_CAVIUM
 
          If unsure, say Y.
 
+config HW_RANDOM_MTK
+	tristate "Mediatek Random Number Generator support"
+	depends on HW_RANDOM
+	depends on ARCH_MEDIATEK || COMPILE_TEST
+	default y
+	---help---
+	  This driver provides kernel-side support for the Random Number
+	  Generator hardware found on Mediatek SoCs.
+
+	  To compile this driver as a module, choose M here. the
+	  module will be called mtk-rng.
+
+	  If unsure, say Y.
+
 endif # HW_RANDOM
 
 config UML_RANDOM
diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
index 5f52b1e..59eacb7 100644
--- a/drivers/char/hw_random/Makefile
+++ b/drivers/char/hw_random/Makefile
@@ -36,3 +36,4 @@ obj-$(CONFIG_HW_RANDOM_STM32) += stm32-rng.o
 obj-$(CONFIG_HW_RANDOM_PIC32) += pic32-rng.o
 obj-$(CONFIG_HW_RANDOM_MESON) += meson-rng.o
 obj-$(CONFIG_HW_RANDOM_CAVIUM) += cavium-rng.o cavium-rng-vf.o
+obj-$(CONFIG_HW_RANDOM_MTK)	+= mtk-rng.o
diff --git a/drivers/char/hw_random/mtk-rng.c b/drivers/char/hw_random/mtk-rng.c
new file mode 100644
index 0000000..df8eb54
--- /dev/null
+++ b/drivers/char/hw_random/mtk-rng.c
@@ -0,0 +1,168 @@
+/*
+ * Driver for Mediatek Hardware Random Number Generator
+ *
+ * Copyright (C) 2017 Sean Wang <sean.wang at mediatek.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+#define MTK_RNG_DEV KBUILD_MODNAME
+
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/hw_random.h>
+#include <linux/io.h>
+#include <linux/iopoll.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+
+#define USEC_POLL			2
+#define TIMEOUT_POLL			20
+
+#define RNG_CTRL			0x00
+#define RNG_EN				BIT(0)
+#define RNG_READY			BIT(31)
+
+#define RNG_DATA			0x08
+
+#define to_mtk_rng(p)	container_of(p, struct mtk_rng, rng)
+
+struct mtk_rng {
+	void __iomem *base;
+	struct clk *clk;
+	struct hwrng rng;
+};
+
+static int mtk_rng_init(struct hwrng *rng)
+{
+	struct mtk_rng *priv = to_mtk_rng(rng);
+	u32 val;
+	int err;
+
+	err = clk_prepare_enable(priv->clk);
+	if (err)
+		return err;
+
+	val = readl(priv->base + RNG_CTRL);
+	val |= RNG_EN;
+	writel(val, priv->base + RNG_CTRL);
+
+	return 0;
+}
+
+static void mtk_rng_cleanup(struct hwrng *rng)
+{
+	struct mtk_rng *priv = to_mtk_rng(rng);
+	u32 val;
+
+	val = readl(priv->base + RNG_CTRL);
+	val &= ~RNG_EN;
+	writel(val, priv->base + RNG_CTRL);
+
+	clk_disable_unprepare(priv->clk);
+}
+
+static bool mtk_rng_wait_ready(struct hwrng *rng, bool wait)
+{
+	struct mtk_rng *priv = to_mtk_rng(rng);
+	int ready;
+
+	ready = readl(priv->base + RNG_CTRL) & RNG_READY;
+	if (!ready && wait)
+		readl_poll_timeout_atomic(priv->base + RNG_CTRL, ready,
+					  ready & RNG_READY, USEC_POLL,
+					  TIMEOUT_POLL);
+	return !!ready;
+}
+
+static int mtk_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
+{
+	struct mtk_rng *priv = to_mtk_rng(rng);
+	int retval = 0;
+
+	while (max >= sizeof(u32)) {
+		if (!mtk_rng_wait_ready(rng, wait))
+			break;
+
+		*(u32 *)buf = readl(priv->base + RNG_DATA);
+		retval += sizeof(u32);
+		buf += sizeof(u32);
+		max -= sizeof(u32);
+	}
+
+	return retval || !wait ? retval : -EIO;
+}
+
+static int mtk_rng_probe(struct platform_device *pdev)
+{
+	struct resource *res;
+	int ret;
+	struct mtk_rng *priv;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res) {
+		dev_err(&pdev->dev, "no iomem resource\n");
+		return -ENXIO;
+	}
+
+	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->rng.name = pdev->name;
+	priv->rng.init = mtk_rng_init;
+	priv->rng.cleanup = mtk_rng_cleanup;
+	priv->rng.read = mtk_rng_read;
+
+	priv->clk = devm_clk_get(&pdev->dev, "rng");
+	if (IS_ERR(priv->clk)) {
+		ret = PTR_ERR(priv->clk);
+		dev_err(&pdev->dev, "no clock for device: %d\n", ret);
+		return ret;
+	}
+
+	priv->base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(priv->base))
+		return PTR_ERR(priv->base);
+
+	ret = devm_hwrng_register(&pdev->dev, &priv->rng);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to register rng device: %d\n",
+			ret);
+		return ret;
+	}
+
+	dev_info(&pdev->dev, "registered RNG driver\n");
+
+	return 0;
+}
+
+static const struct of_device_id mtk_rng_match[] = {
+	{ .compatible = "mediatek,mt7623-rng" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, mtk_rng_match);
+
+static struct platform_driver mtk_rng_driver = {
+	.probe          = mtk_rng_probe,
+	.driver = {
+		.name = MTK_RNG_DEV,
+		.of_match_table = mtk_rng_match,
+	},
+};
+
+module_platform_driver(mtk_rng_driver);
+
+MODULE_DESCRIPTION("Mediatek Random Number Generator Driver");
+MODULE_AUTHOR("Sean Wang <sean.wang at mediatek.com>");
+MODULE_LICENSE("GPL");
-- 
1.9.1