[v2,2/2] hwrng: add support for Airoha EN7581 TRNG

diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
index 5912c2dd6398..bda283f290bc 100644
--- a/drivers/char/hw_random/Kconfig
+++ b/drivers/char/hw_random/Kconfig
@@ -62,6 +62,19 @@  config HW_RANDOM_AMD
 
 	  If unsure, say Y.
 
+config HW_RANDOM_AIROHA
+	tristate "Airoha True HW Random Number Generator support"
+	depends on ARCH_AIROHA || COMPILE_TEST
+	default HW_RANDOM
+	help
+	  This driver provides kernel-side support for the True Random Number
+	  Generator hardware found on Airoha SoC.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called airoha-rng.
+
+	  If unsure, say Y.
+
 config HW_RANDOM_ATMEL
 	tristate "Atmel Random Number Generator support"
 	depends on (ARCH_AT91 || COMPILE_TEST)
diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
index 01f012eab440..dfb717b12f0b 100644
--- a/drivers/char/hw_random/Makefile
+++ b/drivers/char/hw_random/Makefile
@@ -8,6 +8,7 @@  rng-core-y := core.o
 obj-$(CONFIG_HW_RANDOM_TIMERIOMEM) += timeriomem-rng.o
 obj-$(CONFIG_HW_RANDOM_INTEL) += intel-rng.o
 obj-$(CONFIG_HW_RANDOM_AMD) += amd-rng.o
+obj-$(CONFIG_HW_RANDOM_AIROHA) += airoha-trng.o
 obj-$(CONFIG_HW_RANDOM_ATMEL) += atmel-rng.o
 obj-$(CONFIG_HW_RANDOM_BA431) += ba431-rng.o
 obj-$(CONFIG_HW_RANDOM_GEODE) += geode-rng.o
diff --git a/drivers/char/hw_random/airoha-trng.c b/drivers/char/hw_random/airoha-trng.c
new file mode 100644
index 000000000000..1dbfa9505c21
--- /dev/null
+++ b/drivers/char/hw_random/airoha-trng.c
@@ -0,0 +1,243 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) 2024 Christian Marangi */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+#include <linux/bitfield.h>
+#include <linux/delay.h>
+#include <linux/hw_random.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/iopoll.h>
+#include <linux/platform_device.h>
+
+#define TRNG_IP_RDY			0x800
+#define   CNT_TRANS			GENMASK(15, 8)
+#define   SAMPLE_RDY			BIT(0)
+#define TRNG_NS_SEK_AND_DAT_EN		0x804
+#define	  RNG_EN			BIT(31) /* referenced as ring_en */
+#define	  RAW_DATA_EN			BIT(16)
+#define TRNG_HEALTH_TEST_SW_RST		0x808
+#define   SW_RST			BIT(0) /* Active High */
+#define TRNG_INTR_EN			0x818
+#define   INTR_MASK			BIT(16)
+#define   CONTINUOUS_HEALTH_INITR_EN	BIT(2)
+#define   SW_STARTUP_INITR_EN		BIT(1)
+#define   RST_STARTUP_INITR_EN		BIT(0)
+/* Notice that Health Test are done only out of Reset and with RNG_EN */
+#define TRNG_HEALTH_TEST_STATUS		0x824
+#define   CONTINUOUS_HEALTH_AP_TEST_FAIL BIT(23)
+#define   CONTINUOUS_HEALTH_RC_TEST_FAIL BIT(22)
+#define   SW_STARTUP_TEST_DONE		BIT(21)
+#define   SW_STARTUP_AP_TEST_FAIL	BIT(20)
+#define   SW_STARTUP_RC_TEST_FAIL	BIT(19)
+#define   RST_STARTUP_TEST_DONE		BIT(18)
+#define   RST_STARTUP_AP_TEST_FAIL	BIT(17)
+#define   RST_STARTUP_RC_TEST_FAIL	BIT(16)
+#define   RAW_DATA_VALID		BIT(7)
+
+#define TRNG_RAW_DATA_OUT		0x828
+
+#define TRNG_CNT_TRANS_VALID		0x80
+#define BUSY_LOOP_SLEEP			10
+#define BUSY_LOOP_TIMEOUT		(BUSY_LOOP_SLEEP * 10000)
+
+struct airoha_trng {
+	void __iomem *base;
+	struct hwrng rng;
+	struct device *dev;
+
+	struct completion rng_op_done;
+};
+
+static int airoha_trng_irq_mask(struct airoha_trng *trng)
+{
+	u32 val;
+
+	val = readl(trng->base + TRNG_INTR_EN);
+	val |= INTR_MASK;
+	writel(val, trng->base + TRNG_INTR_EN);
+
+	return 0;
+}
+
+static int airoha_trng_irq_unmask(struct airoha_trng *trng)
+{
+	u32 val;
+
+	val = readl(trng->base + TRNG_INTR_EN);
+	val &= ~INTR_MASK;
+	writel(val, trng->base + TRNG_INTR_EN);
+
+	return 0;
+}
+
+static int airoha_trng_init(struct hwrng *rng)
+{
+	struct airoha_trng *trng = container_of(rng, struct airoha_trng, rng);
+	int ret;
+	u32 val;
+
+	val = readl(trng->base + TRNG_NS_SEK_AND_DAT_EN);
+	val |= RNG_EN;
+	writel(val, trng->base + TRNG_NS_SEK_AND_DAT_EN);
+
+	/* Set out of SW Reset */
+	airoha_trng_irq_unmask(trng);
+	writel(0, trng->base + TRNG_HEALTH_TEST_SW_RST);
+
+	ret = wait_for_completion_timeout(&trng->rng_op_done, BUSY_LOOP_TIMEOUT);
+	if (ret <= 0) {
+		dev_err(trng->dev, "Timeout waiting for Health Check\n");
+		airoha_trng_irq_mask(trng);
+		return -ENODEV;
+	}
+
+	/* Check if Health Test Failed */
+	val = readl(trng->base + TRNG_HEALTH_TEST_STATUS);
+	if (val & (RST_STARTUP_AP_TEST_FAIL | RST_STARTUP_RC_TEST_FAIL)) {
+		dev_err(trng->dev, "Health Check fail: %s test fail\n",
+			val & RST_STARTUP_AP_TEST_FAIL ? "AP" : "RC");
+		return -ENODEV;
+	}
+
+	/* Check if IP is ready */
+	ret = readl_poll_timeout(trng->base + TRNG_IP_RDY, val,
+				 val & SAMPLE_RDY, 10, 1000);
+	if (ret < 0) {
+		dev_err(trng->dev, "Timeout waiting for IP ready");
+		return -ENODEV;
+	}
+
+	/* CNT_TRANS must be 0x80 for IP to be considered ready */
+	ret = readl_poll_timeout(trng->base + TRNG_IP_RDY, val,
+				 FIELD_GET(CNT_TRANS, val) == TRNG_CNT_TRANS_VALID,
+				 10, 1000);
+	if (ret < 0) {
+		dev_err(trng->dev, "Timeout waiting for IP ready");
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
+static void airoha_trng_cleanup(struct hwrng *rng)
+{
+	struct airoha_trng *trng = container_of(rng, struct airoha_trng, rng);
+	u32 val;
+
+	val = readl(trng->base + TRNG_NS_SEK_AND_DAT_EN);
+	val &= ~RNG_EN;
+	writel(val, trng->base + TRNG_NS_SEK_AND_DAT_EN);
+
+	/* Put it in SW Reset */
+	writel(SW_RST, trng->base + TRNG_HEALTH_TEST_SW_RST);
+}
+
+static int airoha_trng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
+{
+	struct airoha_trng *trng = container_of(rng, struct airoha_trng, rng);
+	u32 *data = buf;
+	u32 status;
+	int ret;
+
+	ret = readl_poll_timeout(trng->base + TRNG_HEALTH_TEST_STATUS, status,
+				 status & RAW_DATA_VALID, 10, 1000);
+	if (ret < 0) {
+		dev_err(trng->dev, "Timeout waiting for TRNG RAW Data valid\n");
+		return ret;
+	}
+
+	*data = readl(trng->base + TRNG_RAW_DATA_OUT);
+
+	return 4;
+}
+
+static irqreturn_t airoha_trng_irq(int irq, void *priv)
+{
+	struct airoha_trng *trng = (struct airoha_trng *)priv;
+
+	airoha_trng_irq_mask(trng);
+	/* Just complete the task, we will read the value later */
+	complete(&trng->rng_op_done);
+
+	return IRQ_HANDLED;
+}
+
+static int airoha_trng_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct airoha_trng *trng;
+	int irq, ret;
+	u32 val;
+
+	trng = devm_kzalloc(dev, sizeof(*trng), GFP_KERNEL);
+	if (!trng)
+		return -ENOMEM;
+
+	trng->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(trng->base))
+		return PTR_ERR(trng->base);
+
+	irq = platform_get_irq(pdev, 0);
+	if (irq < 0)
+		return irq;
+
+	airoha_trng_irq_mask(trng);
+	ret = devm_request_irq(&pdev->dev, irq, airoha_trng_irq, 0,
+			       pdev->name, (void *)trng);
+	if (ret) {
+		dev_err(dev, "Can't get interrupt working.\n");
+		return ret;
+	}
+
+	init_completion(&trng->rng_op_done);
+
+	/* Enable interrupt for SW reset Health Check */
+	val = readl(trng->base + TRNG_INTR_EN);
+	val |= RST_STARTUP_INITR_EN;
+	writel(val, trng->base + TRNG_INTR_EN);
+
+	/* Set output to raw data */
+	val = readl(trng->base + TRNG_NS_SEK_AND_DAT_EN);
+	val |= RAW_DATA_EN;
+	writel(val, trng->base + TRNG_NS_SEK_AND_DAT_EN);
+
+	/* Put it in SW Reset */
+	writel(SW_RST, trng->base + TRNG_HEALTH_TEST_SW_RST);
+
+	trng->dev = dev;
+	trng->rng.name = pdev->name;
+	trng->rng.init = airoha_trng_init;
+	trng->rng.cleanup = airoha_trng_cleanup;
+	trng->rng.read = airoha_trng_read;
+
+	ret = devm_hwrng_register(dev, &trng->rng);
+	if (ret) {
+		dev_err(dev, "failed to register rng device: %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static const struct of_device_id airoha_trng_of_match[] = {
+	{ .compatible = "airoha,en7581-trng", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, airoha_trng_of_match);
+
+static struct platform_driver airoha_trng_driver = {
+	.driver = {
+		.name = "airoha-trng",
+		.of_match_table	= airoha_trng_of_match,
+	},
+	.probe = airoha_trng_probe,
+};
+
+module_platform_driver(airoha_trng_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Christian Marangi <ansuelsmth@gmail.com>");
+MODULE_DESCRIPTION("Airoha True Random Number Generator driver");