dt-bindings: rng: add support for Airoha EN7581 TRNG

Add support for Airoha TRNG. The Airoha SoC provide a True RNG module that can output 4 bytes of raw data at times.

The module makes use of various noise source to provide True Random Number Generation.

On probe the module is reset to operate Health Test and verify correct execution of it.

The module can also provide DRBG function but the execution mode is mutually exclusive, running as TRNG doesn't permit to also run it as DRBG.

Signed-off-by Christian Marangi <[email protected]>

---
Changes v2:
- Sort include header
- Add missing bitfield.h

 drivers/char/hw_random/Kconfig       |  13 ++
 drivers/char/hw_random/Makefile      |   1 +
 drivers/char/hw_random/airoha-trng.c | 243 +++++++++++++++++++++++++++
 3 files changed, 257 insertions(+)
 create mode 100644 drivers/char/hw_random/airoha-trng.c

drivers/char/hw_random/Kconfig +13 -0

index 5912c2dd6398..bda283f290bc 100644
@@ -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)

drivers/char/hw_random/Makefile +1 -0

index 01f012eab440..dfb717b12f0b 100644
@@ -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

drivers/char/hw_random/airoha-trng.c new file +101 -0

new file mode 100644
index 000000000000..1dbfa9505c21
@@ -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");

Add support for Airoha EN7581 True Random Number generator.

This module can generate up to 4bytes of raw data at times and support self health test at startup. The module gets noise for randomness from various source from ADC, AP, dedicated clocks and other devices attached to the SoC producing true random numbers.

Signed-off-by Christian Marangi <[email protected]>

Reviewed-by Rob Herring (Arm) <[email protected]>

---
Changes v2:
- Add Reviewed-by tag

 .../bindings/rng/airoha,en7581-trng.yaml      | 38 +++++++++++++++++++
 1 file changed, 38 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/rng/airoha,en7581-trng.yaml