From: Sean Wang <sean.w...@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.w...@mediatek.com>
---
 drivers/char/hw_random/Kconfig   |  16 +++-
 drivers/char/hw_random/Makefile  |   2 +-
 drivers/char/hw_random/mtk-rng.c | 174 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 190 insertions(+), 2 deletions(-)
 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..af782ce 100644
--- a/drivers/char/hw_random/Kconfig
+++ b/drivers/char/hw_random/Kconfig
@@ -419,10 +419,24 @@ config HW_RANDOM_CAVIUM
          Generator hardware found on Cavium SoCs.
 
          To compile this driver as a module, choose M here: the
-         module will be called cavium_rng.
+         module will be called mtk-rng.
 
          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..68be716 100644
--- a/drivers/char/hw_random/Makefile
+++ b/drivers/char/hw_random/Makefile
@@ -1,7 +1,6 @@
 #
 # Makefile for HW Random Number Generator (RNG) device drivers.
 #
-
 obj-$(CONFIG_HW_RANDOM) += rng-core.o
 rng-core-y := core.o
 obj-$(CONFIG_HW_RANDOM_TIMERIOMEM) += timeriomem-rng.o
@@ -36,3 +35,4 @@ 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..6561ee0
--- /dev/null
+++ b/drivers/char/hw_random/mtk-rng.c
@@ -0,0 +1,174 @@
+/*
+ * Driver for Mediatek Hardware Random Number Generator
+ *
+ * Copyright (C) 2017 Sean Wang <sean.w...@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 {
+       struct device   *dev;
+       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);
+       }
+
+       if (unlikely(wait && max))
+               dev_warn(priv->dev, "timeout might be not properly set\n");
+
+       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->dev = &pdev->dev;
+       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;
+       }
+
+       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);
+
+       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.w...@mediatek.com>");
+MODULE_LICENSE("GPL");
-- 
1.9.1

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