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Subject[PATCH v4 3/3] hwrng: add mtk-sec-rng driver
Date
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/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..ecd2e29
--- /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)
+{
+ u32 val[4] = {0};
+ int retval = 0;
+ int i;
+
+ while (max >= MTK_SEC_RND_SIZE) {
+ mtk_sec_get_rnd(val);
+
+ for (i = 0; i < SMC_RET_NUM; i++) {
+ *(u32 *)buf = val[i];
+ buf += sizeof(u32);
+ }
+
+ retval += MTK_SEC_RND_SIZE;
+ max -= MTK_SEC_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.liu@mediatek.com>");
+MODULE_LICENSE("GPL");
--
1.7.9.5
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