drivers: entropy: add support for Microchip ATECC608

Add entropy support for Microchip ATECC608
and ATECC508.

Signed-off-by: Fin Maaß <f.maass@vogl-electronic.com>

drivers/entropy/CMakeLists.txt

@@ -4,6 +4,7 @@ zephyr_syscall_header(${ZEPHYR_BASE}/include/zephyr/drivers/entropy.h)
 
 zephyr_library()
 
+zephyr_library_sources_ifdef(CONFIG_ENTROPY_ATECCX08           entropy_ateccx08.c)
 zephyr_library_sources_ifdef(CONFIG_ENTROPY_TELINK_B91_TRNG    entropy_b91_trng.c)
 zephyr_library_sources_ifdef(CONFIG_ENTROPY_CC13XX_CC26XX_RNG  entropy_cc13xx_cc26xx.c)
 zephyr_library_sources_ifdef(CONFIG_ENTROPY_ESP32_RNG          entropy_esp32.c)

drivers/entropy/Kconfig

@@ -20,6 +20,7 @@ config ENTROPY_INIT_PRIORITY
 	help
 	  Entropy driver device initialization priority.
 
+source "drivers/entropy/Kconfig.ateccx08"
 source "drivers/entropy/Kconfig.b91"
 source "drivers/entropy/Kconfig.cc13xx_cc26xx"
 source "drivers/entropy/Kconfig.mcux"

drivers/entropy/Kconfig.ateccx08

@@ -0,0 +1,13 @@
+# Microchip ATECCx08 entropy generator driver configuration
+
+# Copyright (c) 2024 Vogl Electronic GmbH
+# SPDX-License-Identifier: Apache-2.0
+
+config ENTROPY_ATECCX08
+	bool "Microchip ATECCx08 RNG driver"
+	default y
+	depends on DT_HAS_MICROCHIP_ATECCX08_ENTROPY_ENABLED
+	depends on EEPROM_ATECCX08
+	select ENTROPY_HAS_DRIVER
+	help
+	  This option enables the Microchip ATECCx08 RNG driver.

drivers/entropy/entropy_ateccx08.c

@@ -0,0 +1,75 @@
+/*
+ * Copyright (c) 2024 Vogl Electronic GmbH
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#define DT_DRV_COMPAT microchip_ateccx08_entropy
+
+#include <errno.h>
+#include <string.h>
+#include <zephyr/device.h>
+#include <zephyr/drivers/entropy.h>
+#include <zephyr/drivers/eeprom/ateccx08.h>
+#include <zephyr/init.h>
+#include <zephyr/kernel.h>
+
+#include <zephyr/logging/log.h>
+LOG_MODULE_REGISTER(entropy_ateccx08, CONFIG_ENTROPY_LOG_LEVEL);
+
+struct entropy_ateccx08_config {
+	const struct device *parent;
+};
+
+static int entropy_ateccx08_get_entropy(const struct device *dev, uint8_t *buffer, uint16_t length)
+{
+	const struct entropy_ateccx08_config *config = dev->config;
+	const static uint8_t not_random[] = {0xff, 0xff, 0x00, 0x00, 0xff, 0xff, 0x00, 0x00};
+
+	int ret = 0;
+
+	while (length > 0) {
+		size_t to_copy;
+		uint8_t random_var[32] = {0};
+
+		ret = atecc_calib_random(config->parent, random_var);
+		if (ret < 0) {
+			return ret;
+		}
+
+		if (memcmp(random_var, not_random, sizeof(not_random)) == 0) {
+			LOG_ERR("Config not locked, no random data available.");
+			return -EIO;
+		}
+
+		to_copy = MIN(length, sizeof(random_var));
+
+		memcpy(buffer, random_var, to_copy);
+		buffer += to_copy;
+		length -= to_copy;
+	}
+	return ret;
+}
+
+static int entropy_ateccx08_init(const struct device *dev)
+{
+	const struct entropy_ateccx08_config *config = dev->config;
+
+	if (!device_is_ready(config->parent)) {
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
+static const struct entropy_driver_api entropy_ateccx08_api = {
+	.get_entropy = entropy_ateccx08_get_entropy};
+
+#define DEFINE_ATECCX08_ENTROPY(_num)                                                              \
+	static const struct entropy_ateccx08_config entropy_ateccx08_config##_num = {              \
+		.parent = DEVICE_DT_GET(DT_INST_BUS(_num))};                                       \
+	DEVICE_DT_INST_DEFINE(_num, entropy_ateccx08_init, NULL, NULL,                             \
+			      &entropy_ateccx08_config##_num, POST_KERNEL,                         \
+			      CONFIG_EEPROM_INIT_PRIORITY, &entropy_ateccx08_api);
+
+DT_INST_FOREACH_STATUS_OKAY(DEFINE_ATECCX08_ENTROPY);

dts/bindings/mtd/microchip,ateccx08-base.yaml

@@ -3,6 +3,8 @@
 
 include: ["eeprom-base.yaml", i2c-device.yaml]
 
+bus: ateccx08
+
 properties:
   size:
     required: true

dts/bindings/rng/microchip,ateccx08-entropy.yaml

@@ -0,0 +1,10 @@
+# Copyright (c) 2024 Vogl Electronic GmbH
+# SPDX-License-Identifier: Apache-2.0
+
+description: Microchip ATECCx08 entropy binding
+
+compatible: "microchip,ateccx08-entropy"
+
+include: base.yaml
+
+on-bus: ateccx08