[PATCH 3/3] hwrng: add mt67xx-rng driver

[<neal.liu@mediatek.com>]

From: Neal Liu <neal.liu@mediatek.com>

For Mediatek SoCs on ARMv8 with TrustZone enabled, peripherals like
entropy sources is not accessible from normal world (linux) and
rather accessible from secure world (ATF/TEE) only. This driver aims
to provide a generic interface to ATF rng service.

Signed-off-by: Neal Liu <neal.liu@mediatek.com>
---
 drivers/char/hw_random/Kconfig      |   16 ++++++
 drivers/char/hw_random/Makefile     |    1 +
 drivers/char/hw_random/mt67xx-rng.c |  104 +++++++++++++++++++++++++++++++++++
 3 files changed, 121 insertions(+)
 create mode 100644 drivers/char/hw_random/mt67xx-rng.c

diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
index 25a7d8f..98751d3 100644
--- a/drivers/char/hw_random/Kconfig
+++ b/drivers/char/hw_random/Kconfig
@@ -398,6 +398,22 @@ config HW_RANDOM_MTK
 
 	  If unsure, say Y.
 
+config HW_RANDOM_MT67XX
+	tristate "Mediatek MT67XX Random Number Generator support"
+	depends on HW_RANDOM
+	depends on ARCH_MEDIATEK || COMPILE_TEST
+	default HW_RANDOM
+	help
+	  This driver provides kernel-side support for the Random Number
+	  Generator hardware found on Mediatek MT67xx SoCs. The difference
+	  with mtk-rng is the Random Number Generator hardware is secure
+	  access only.
+
+	  To compile this driver as a module, choose M here. the
+	  module will be called mt67xx-rng.
+
+	  If unsure, say Y.
+
 config HW_RANDOM_S390
 	tristate "S390 True Random Number Generator support"
 	depends on S390
diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
index 7c9ef4a..4be95ab 100644
--- a/drivers/char/hw_random/Makefile
+++ b/drivers/char/hw_random/Makefile
@@ -36,6 +36,7 @@ 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
+obj-$(CONFIG_HW_RANDOM_MT67XX) += mt67xx-rng.o
 obj-$(CONFIG_HW_RANDOM_S390) += s390-trng.o
 obj-$(CONFIG_HW_RANDOM_KEYSTONE) += ks-sa-rng.o
 obj-$(CONFIG_HW_RANDOM_OPTEE) += optee-rng.o
diff --git a/drivers/char/hw_random/mt67xx-rng.c b/drivers/char/hw_random/mt67xx-rng.c
new file mode 100644
index 0000000..e70cbbe
--- /dev/null
+++ b/drivers/char/hw_random/mt67xx-rng.c
@@ -0,0 +1,104 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019 MediaTek Inc.
+ */
+
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/hw_random.h>
+#include <linux/of.h>
+#include <linux/arm-smccc.h>
+#include <linux/soc/mediatek/mtk_sip_svc.h>
+
+#define PFX			KBUILD_MODNAME ": "
+#define MT67XX_RNG_MAGIC	0x74726e67
+#define SMC_RET_NUM		4
+
+struct mt67xx_rng_priv {
+	struct hwrng rng;
+};
+
+
+static void __rng_sec_read(uint32_t *val)
+{
+	struct arm_smccc_res res;
+
+	arm_smccc_smc(MTK_SIP_KERNEL_GET_RND,
+		      MT67XX_RNG_MAGIC, 0, 0, 0, 0, 0, 0, &res);
+
+	val[0] = res.a0;
+	val[1] = res.a1;
+	val[2] = res.a2;
+	val[3] = res.a3;
+}
+
+static int mt67xx_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
+{
+	int i, retval = 0;
+	uint32_t val[4] = {0};
+	size_t get_rnd_size = sizeof(u32) * SMC_RET_NUM;
+
+	if (!buf) {
+		pr_err("%s, buf is NULL\n", __func__);
+		return -EFAULT;
+	}
+
+	while (max >= get_rnd_size) {
+		__rng_sec_read(val);
+
+		for (i = 0; i < SMC_RET_NUM; i++) {
+			*(u32 *)buf = val[i];
+			buf += sizeof(u32);
+		}
+
+		retval += get_rnd_size;
+		max -= get_rnd_size;
+	}
+
+	return retval;
+}
+
+static int mt67xx_rng_probe(struct platform_device *pdev)
+{
+	int ret;
+	struct mt67xx_rng_priv *priv;
+
+	pr_info(PFX "driver registered\n");
+	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->rng.name = KBUILD_MODNAME;
+	priv->rng.read = mt67xx_rng_read;
+	priv->rng.priv = (unsigned long)&pdev->dev;
+	priv->rng.quality = 900;
+
+	ret = devm_hwrng_register(&pdev->dev, &priv->rng);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to register rng device: %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static const struct of_device_id mt67xx_rng_match[] = {
+	{ .compatible = "mediatek,mt67xx-rng", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, mt67xx_rng_match);
+
+static struct platform_driver mt67xx_rng_driver = {
+	.probe = mt67xx_rng_probe,
+	.driver = {
+		.name = KBUILD_MODNAME,
+		.owner = THIS_MODULE,
+		.of_match_table = mt67xx_rng_match,
+	},
+};
+
+module_platform_driver(mt67xx_rng_driver);
+
+MODULE_DESCRIPTION("Mediatek MT67XX Random Number Generator Driver");
+MODULE_AUTHOR("Neal Liu <neal.liu@mediatek.com>");
+MODULE_LICENSE("GPL");
-- 
1.7.9.5