drivers: entropy: mspm0: Add a support for TI MSPM0 TRNG module

TI MSPM0 has a TRNG module to generate truly random bits. Add a support
for TI MSPM0 TRNG module.

Signed-off-by: Sanjay Vallimanalan <[email protected]>

Author: SanjayyyV

drivers/entropy/CMakeLists.txt

@@ -25,6 +25,7 @@ zephyr_library_sources_ifdef(CONFIG_ENTROPY_MCUX_CAAM           entropy_mcux_caa
 zephyr_library_sources_ifdef(CONFIG_ENTROPY_MCUX_RNG            entropy_mcux_rng.c)
 zephyr_library_sources_ifdef(CONFIG_ENTROPY_MCUX_RNGA           entropy_mcux_rnga.c)
 zephyr_library_sources_ifdef(CONFIG_ENTROPY_MCUX_TRNG           entropy_mcux_trng.c)
+zephyr_library_sources_ifdef(CONFIG_ENTROPY_MSPM0_TRNG          entropy_mspm0_trng.c)
 zephyr_library_sources_ifdef(CONFIG_ENTROPY_NEORV32_TRNG        entropy_neorv32_trng.c)
 zephyr_library_sources_ifdef(CONFIG_ENTROPY_NPCX_DRBG           entropy_npcx_drbg.c)
 zephyr_library_sources_ifdef(CONFIG_ENTROPY_NRF5_RNG            entropy_nrf5.c)

drivers/entropy/Kconfig

@@ -31,6 +31,7 @@ source "drivers/entropy/Kconfig.litex"
 source "drivers/entropy/Kconfig.max32"
 source "drivers/entropy/Kconfig.maxq10xx"
 source "drivers/entropy/Kconfig.mcux"
+source "drivers/entropy/Kconfig.mspm0_trng"
 source "drivers/entropy/Kconfig.native_sim"
 source "drivers/entropy/Kconfig.neorv32"
 source "drivers/entropy/Kconfig.npcx"

drivers/entropy/Kconfig.mspm0_trng

@@ -0,0 +1,32 @@
+# Copyright (c) 2025, Linumiz GmbH
+# SPDX-License-Identifier: Apache-2.0
+
+config ENTROPY_MSPM0_TRNG
+	bool "TI MSPM0 True Random Number Generator (TRNG)"
+	default y
+	depends on DT_HAS_TI_MSPM0_TRNG_ENABLED
+	depends on SOC_FAMILY_TI_MSPM0
+	select ENTROPY_HAS_DRIVER
+	select RING_BUFFER
+	help
+	  This option enables the driver for the True Random Number Generator (TRNG)
+	  for TI MSPM0 SoCs.
+
+if ENTROPY_MSPM0_TRNG
+
+config ENTROPY_MSPM0_TRNG_POOL_SIZE
+	int "Entropy pool buffer size in bytes"
+	default 256
+	help
+	  The size in bytes of the ring buffer used to store entropy generated by the
+	  TRNG hardware.
+
+config ENTROPY_MSPM0_TRNG_DECIMATION_RATE
+	int "TRNG decimation rate (0-7)"
+	default 4
+	range 0 7
+	help
+	  The decimation rate controls the sampling rate of the TRNG. Higher values
+	  provide better entropy quality. A decimation rate of 4 or greater is recommended per TRM.
+	  Valid values are 0-7.
+endif # ENTROPY_MSPM0_TRNG

drivers/entropy/entropy_mspm0_trng.c

@@ -0,0 +1,236 @@
+/*
+ * Copyright (c) 2025 Linumiz GmbH
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#define DT_DRV_COMPAT ti_mspm0_trng
+
+#include <zephyr/kernel.h>
+#include <zephyr/device.h>
+#include <zephyr/drivers/entropy.h>
+#include <zephyr/irq.h>
+#include <zephyr/logging/log.h>
+#include <zephyr/sys/ring_buffer.h>
+
+/* TI Driverlib includes */
+#include <ti/driverlib/dl_trng.h>
+#include <ti/devices/msp/peripherals/hw_trng.h>
+
+#define TRNG_BUFFER_SIZE	CONFIG_ENTROPY_MSPM0_TRNG_POOL_SIZE
+#define TRNG_DECIMATION_RATE	CONFIG_ENTROPY_MSPM0_TRNG_DECIMATION_RATE
+#define TRNG_SAMPLE_SIZE	4
+
+#define TRNG_CLOCK_DIVIDE_RATIO		CONCAT(DL_TRNG_CLOCK_DIVIDE_, DT_INST_PROP(0, ti_clk_div))
+
+#define TRNG_SAMPLE_GENERATE_TIME	(1000000 * (32 * (TRNG_DECIMATION_RATE + 1)) \
+		/ (CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC / (TRNG_CLOCK_DIVIDE_RATIO)))
+
+struct entropy_mspm0_trng_config {
+	TRNG_Regs *base;
+};
+
+struct entropy_mspm0_trng_data {
+	struct k_sem sem_lock;
+	struct k_sem sem_sync;
+	struct ring_buf entropy_pool;
+	uint8_t pool_buffer[TRNG_BUFFER_SIZE];
+};
+
+static void entropy_mspm0_trng_isr(const struct device *dev)
+{
+	const struct entropy_mspm0_trng_config *config = dev->config;
+	struct entropy_mspm0_trng_data *data = dev->data;
+	uint32_t status;
+	uint32_t entropy_data;
+	uint8_t dig_test;
+	uint8_t ana_test;
+	uint32_t bytes_written;
+
+	status = DL_TRNG_getEnabledInterruptStatus(config->base,
+						   DL_TRNG_INTERRUPT_CAPTURE_RDY_EVENT |
+						   DL_TRNG_INTERRUPT_HEALTH_FAIL_EVENT |
+						   DL_TRNG_INTERRUPT_CMD_DONE_EVENT);
+
+	if ((status & DL_TRNG_INTERRUPT_HEALTH_FAIL_EVENT)) {
+		DL_TRNG_clearInterruptStatus(config->base, DL_TRNG_INTERRUPT_HEALTH_FAIL_EVENT);
+		DL_TRNG_sendCommand(config->base, DL_TRNG_CMD_PWROFF);
+		return;
+	}
+
+	if (status & DL_TRNG_INTERRUPT_CMD_DONE_EVENT) {
+		DL_TRNG_clearInterruptStatus(config->base, DL_TRNG_INTERRUPT_CMD_DONE_EVENT);
+
+		/* Run DIG test */
+		dig_test = DL_TRNG_getDigitalHealthTestResults(config->base);
+		if (!dig_test) {
+			DL_TRNG_sendCommand(config->base, DL_TRNG_CMD_TEST_DIG);
+			return;
+		}
+
+		/* Run ANALOG test */
+		ana_test = DL_TRNG_getAnalogHealthTestResults(config->base);
+		if (!ana_test) {
+			DL_TRNG_sendCommand(config->base, DL_TRNG_CMD_TEST_ANA);
+			return;
+		}
+
+		/*
+		 * If both tests are successful, set DECIM RATE, enable IRQ_CAPTURE_RDY
+		 * and discard first sample from DATA_CAPTURE register
+		 */
+		if ((dig_test == DL_TRNG_DIGITAL_HEALTH_TEST_SUCCESS) &&
+		     (ana_test == DL_TRNG_ANALOG_HEALTH_TEST_SUCCESS)) {
+			DL_TRNG_clearInterruptStatus(config->base,
+						     DL_TRNG_INTERRUPT_CAPTURE_RDY_EVENT);
+			DL_TRNG_setDecimationRate(config->base,
+						  (DL_TRNG_DECIMATION_RATE)TRNG_DECIMATION_RATE);
+			DL_TRNG_disableInterrupt(config->base, DL_TRNG_INTERRUPT_CMD_DONE_EVENT);
+			DL_TRNG_enableInterrupt(config->base, DL_TRNG_INTERRUPT_CAPTURE_RDY_EVENT);
+			DL_TRNG_getCapture(config->base);
+			return;
+		}
+	}
+
+	if ((status & DL_TRNG_INTERRUPT_CAPTURE_RDY_EVENT)) {
+		entropy_data = DL_TRNG_getCapture(config->base);
+		bytes_written = ring_buf_put(&data->entropy_pool, (uint8_t *)&entropy_data,
+					     TRNG_SAMPLE_SIZE);
+
+		/* If the ring buf is exhausted, disable the interrupt in IMASK */
+		if (bytes_written != TRNG_SAMPLE_SIZE) {
+			DL_TRNG_disableInterrupt(config->base, DL_TRNG_INTERRUPT_CAPTURE_RDY_EVENT);
+		}
+
+		DL_TRNG_clearInterruptStatus(config->base, DL_TRNG_INTERRUPT_CAPTURE_RDY_EVENT);
+		k_sem_give(&data->sem_sync);
+	}
+}
+
+static int entropy_mspm0_trng_get_entropy(const struct device *dev,
+					  uint8_t *buffer, uint16_t length)
+{
+	const struct entropy_mspm0_trng_config *config = dev->config;
+	struct entropy_mspm0_trng_data *data = dev->data;
+	uint16_t bytes_read;
+
+	while (length) {
+		k_sem_take(&data->sem_lock, K_FOREVER);
+		bytes_read = ring_buf_get(&data->entropy_pool, buffer, length);
+		k_sem_give(&data->sem_lock);
+
+		/*
+		 * If no bytes read, i.e ring buf is exhausted, enable the interrupt and
+		 * wait until the additional entropy is available in ring buf.
+		 */
+		if (bytes_read == 0U) {
+			DL_TRNG_enableInterrupt(config->base,
+						DL_TRNG_INTERRUPT_CAPTURE_RDY_EVENT);
+			k_sem_take(&data->sem_sync, K_FOREVER);
+			continue;
+		}
+
+		buffer += bytes_read;
+		length -= bytes_read;
+	}
+
+	return 0;
+}
+
+static int entropy_mspm0_trng_get_entropy_isr(const struct device *dev, uint8_t *buffer,
+					      uint16_t length, uint32_t flags)
+{
+	const struct entropy_mspm0_trng_config *config = dev->config;
+	struct entropy_mspm0_trng_data *data = dev->data;
+	uint16_t bytes_read;
+	uint16_t total_read;
+	uint32_t entropy_data;
+	unsigned int key;
+
+	/* Try to get entropy from existing ring buffer */
+	bytes_read = ring_buf_get(&data->entropy_pool, buffer, length);
+	total_read = bytes_read;
+
+	if ((bytes_read == length) || ((flags & ENTROPY_BUSYWAIT) == 0U)) {
+		/* Either we got all requested data, or busy-waiting is not allowed */
+		return total_read;
+	}
+
+	/* Busy-wait for additional data (only if ENTROPY_BUSYWAIT is set) */
+	buffer += bytes_read;
+	length -= bytes_read;
+
+	while (length) {
+		key = irq_lock();
+
+		/* Check if data is ready by checking IRQ_CAPTURED_RDY */
+		if (DL_TRNG_isCaptureReady(config->base)) {
+			entropy_data = DL_TRNG_getCapture(config->base);
+			ring_buf_put(&data->entropy_pool, (uint8_t *)&entropy_data,
+				     TRNG_SAMPLE_SIZE);
+		}
+
+		bytes_read = ring_buf_get(&data->entropy_pool, buffer, length);
+
+		irq_unlock(key);
+
+		if (bytes_read) {
+			buffer += bytes_read;
+			length -= bytes_read;
+			total_read += bytes_read;
+		} else {
+			k_busy_wait(TRNG_SAMPLE_GENERATE_TIME);
+		}
+	}
+
+	return total_read;
+}
+
+static int entropy_mspm0_trng_init(const struct device *dev)
+{
+	const struct entropy_mspm0_trng_config *config = dev->config;
+	struct entropy_mspm0_trng_data *data = dev->data;
+
+	/* Initialize ring buffer for entropy storage */
+	ring_buf_init(&data->entropy_pool, sizeof(data->pool_buffer), data->pool_buffer);
+
+	/* Enable TRNG power */
+	DL_TRNG_enablePower(config->base);
+
+	/* Configure TRNG clock divider */
+	DL_TRNG_setClockDivider(config->base, TRNG_CLOCK_DIVIDE_RATIO);
+
+	/* Disable the CAPTURE_RDY IRQ until health tests are complete */
+	DL_TRNG_disableInterrupt(config->base, DL_TRNG_INTERRUPT_CAPTURE_RDY_EVENT);
+	DL_TRNG_enableInterrupt(config->base, DL_TRNG_INTERRUPT_CMD_DONE_EVENT |
+					      DL_TRNG_INTERRUPT_HEALTH_FAIL_EVENT);
+
+	/* Move TRNG from OFF to NORM FUNC state */
+	DL_TRNG_sendCommand(config->base, DL_TRNG_CMD_NORM_FUNC);
+
+	IRQ_CONNECT(DT_INST_IRQN(0), DT_INST_IRQ(0, priority),
+		    entropy_mspm0_trng_isr, DEVICE_DT_INST_GET(0), 0);
+	irq_enable(DT_INST_IRQN(0));
+
+	return 0;
+}
+
+static const struct entropy_driver_api entropy_mspm0_trng_driver_api = {
+	.get_entropy = entropy_mspm0_trng_get_entropy,
+	.get_entropy_isr = entropy_mspm0_trng_get_entropy_isr,
+};
+
+static const struct entropy_mspm0_trng_config entropy_mspm0_trng_config = {
+	.base = (TRNG_Regs *)DT_INST_REG_ADDR(0),
+};
+
+static struct entropy_mspm0_trng_data entropy_mspm0_trng_data = {
+	.sem_lock = Z_SEM_INITIALIZER(entropy_mspm0_trng_data.sem_lock, 1, 1),
+	.sem_sync = Z_SEM_INITIALIZER(entropy_mspm0_trng_data.sem_sync, 0, 1),
+};
+
+DEVICE_DT_INST_DEFINE(0, entropy_mspm0_trng_init, NULL,
+		      &entropy_mspm0_trng_data,
+		      &entropy_mspm0_trng_config, PRE_KERNEL_1,
+		      CONFIG_ENTROPY_INIT_PRIORITY,
+		      &entropy_mspm0_trng_driver_api);