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....@mediatek.com>
---
 drivers/char/hw_random/Kconfig       |   16 ++++++
 drivers/char/hw_random/Makefile      |    1 +
 drivers/char/hw_random/mtk-sec-rng.c |   97 ++++++++++++++++++++++++++++++++++
 3 files changed, 114 insertions(+)
 create mode 100644 drivers/char/hw_random/mtk-sec-rng.c

diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
index 25a7d8f..6c82a3b 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_MTK_SEC
+       tristate "MediaTek Security 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 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 mtk-sec-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..0ae4993 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-$(CONFIG_HW_RANDOM_MTK_SEC) += mtk-sec-rng.o
 obj-$(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/mtk-sec-rng.c 
b/drivers/char/hw_random/mtk-sec-rng.c
new file mode 100644
index 0000000..4c6e5bf
--- /dev/null
+++ b/drivers/char/hw_random/mtk-sec-rng.c
@@ -0,0 +1,97 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019 MediaTek Inc.
+ */
+
+#include <linux/arm-smccc.h>
+#include <linux/hw_random.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/soc/mediatek/mtk_sip_svc.h>
+
+#define MT67XX_RNG_MAGIC       0x74726e67
+#define SMC_RET_NUM            4
+#define MTK_SEC_RND_SIZE       (sizeof(u32) * SMC_RET_NUM)
+
+struct mtk_sec_rng_priv {
+       struct hwrng rng;
+};
+
+static void mtk_sec_get_rnd(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 mtk_sec_rng_read(struct hwrng *rng, void *buf, size_t max, bool 
wait)
+{
+       size_t get_rnd_size = MTK_SEC_RND_SIZE;
+       u32 val[4] = {0};
+       int i, retval = 0;
+
+       while (max >= get_rnd_size) {
+               mtk_sec_get_rnd(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 mtk_sec_rng_probe(struct platform_device *pdev)
+{
+       struct mtk_sec_rng_priv *priv;
+       int ret;
+
+       priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+       if (!priv)
+               return -ENOMEM;
+
+       priv->rng.name = pdev->name;
+       priv->rng.read = mtk_sec_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 mtk_sec_rng_match[] = {
+       { .compatible = "mediatek,mtk-sec-rng", },
+       {}
+};
+MODULE_DEVICE_TABLE(of, mtk_sec_rng_match);
+
+static struct platform_driver mtk_sec_rng_driver = {
+       .probe = mtk_sec_rng_probe,
+       .driver = {
+               .name = KBUILD_MODNAME,
+               .owner = THIS_MODULE,
+               .of_match_table = mtk_sec_rng_match,
+       },
+};
+
+module_platform_driver(mtk_sec_rng_driver);
+
+MODULE_DESCRIPTION("MediaTek Security Random Number Generator Driver");
+MODULE_AUTHOR("Neal Liu <neal....@mediatek.com>");
+MODULE_LICENSE("GPL");
-- 
1.7.9.5

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