drivers: entropy: Introduce driver for SiWx917

Support for random number generator is required for most of the
cryptographic operations, including support for WiFi and TLS.

This driver has been tested with tests/drivers/entropy:

    *** Booting Zephyr OS build v3.7.0-4339-g1ec5ce05f9f8 ***
    Running TESTSUITE entropy_api
    ===================================================================
    START - test_entropy_get_entropy
    random device is 0x8217298, name is rng@45090000
      0x93
      0x3e
      0xf1
      0x68
      0xd4
      0x22
      0xbf
      0x4d
      0xad
     PASS - test_entropy_get_entropy in 0.012 seconds
    ===================================================================
    TESTSUITE entropy_api succeeded

    ------ TESTSUITE SUMMARY START ------

    SUITE PASS - 100.00% [entropy_api]: pass = 1, fail = 0, skip = 0 ...
     - PASS - [entropy_api.test_entropy_get_entropy] duration = 0.01 ...

    ------ TESTSUITE SUMMARY END ------

    ===================================================================
    RunID: d1547c805699201af769cb01331efcce
    PROJECT EXECUTION SUCCESSFUL

Co-authored-by: Tibor Laczko <[email protected]>
Signed-off-by: Tibor Laczko <[email protected]>
Signed-off-by: Jérôme Pouiller <[email protected]>

Author: jerome-pouiller

drivers/CMakeLists.txt

@@ -2,6 +2,7 @@
 # SPDX-License-Identifier: Apache-2.0
 
 add_subdirectory(bluetooth)
+add_subdirectory(entropy)
 add_subdirectory(gpio)
 add_subdirectory(pinctrl)
 add_subdirectory(wifi)

drivers/entropy/CMakeLists.txt

@@ -0,0 +1,5 @@
+# Copyright (c) 2024 Silicon Laboratories Inc.
+# SPDX-License-Identifier: Apache-2.0
+
+zephyr_library_amend()
+zephyr_library_sources_ifdef(CONFIG_ENTROPY_SILABS_SIWX917 entropy_silabs_siwx917.c)

drivers/entropy/Kconfig

@@ -0,0 +1,8 @@
+# Copyright (c) 2024 Silicon Laboratories Inc.
+# SPDX-License-Identifier: Apache-2.0
+
+if ENTROPY_GENERATOR
+
+rsource "Kconfig.siwx917"
+
+endif

drivers/entropy/Kconfig.siwx917

@@ -0,0 +1,11 @@
+# Copyright (c) 2024 Silicon Laboratories Inc.
+# SPDX-License-Identifier: Apache-2.0
+
+config ENTROPY_SILABS_SIWX917
+	bool "SiWx917 RNG driver"
+	default y
+	depends on DT_HAS_SILABS_SIWX917_RNG_ENABLED
+	select ENTROPY_HAS_DRIVER
+	help
+	 Enable hardware Random Number Generator embedded on Silicon Labs
+	 SiWx917 chips.

drivers/entropy/entropy_silabs_siwx917.c

@@ -0,0 +1,61 @@
+/*
+ * Copyright (c) 2024 Silicon Laboratories Inc.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+#define DT_DRV_COMPAT silabs_siwx917_rng
+
+#include <zephyr/drivers/entropy.h>
+
+#include "rsi_rom_rng.h"
+#include "rsi_rom_clks.h"
+
+static int siwx917_get_entropy_isr(const struct device *dev, uint8_t *buffer,
+				   uint16_t length, uint32_t flags)
+{
+	uint32_t u32_count = length / sizeof(uint32_t);
+	uint32_t u8_count = u32_count * sizeof(uint32_t);
+	uint32_t u8_remainder = length - u8_count;
+	uint32_t swap_space;
+
+	if (!(flags & ENTROPY_BUSYWAIT)) {
+		return -ENOTSUP;
+	}
+	RSI_RNG_GetBytes((void *)dev->config, (uint32_t *)buffer, u32_count);
+	if (length % sizeof(uint32_t)) {
+		RSI_RNG_GetBytes((void *)dev->config, &swap_space, 1);
+		memcpy(buffer + u8_count, &swap_space, u8_remainder);
+	}
+
+	return 0;
+}
+
+static int siwx917_get_entropy(const struct device *dev, uint8_t *buffer, uint16_t length)
+{
+	return siwx917_get_entropy_isr(dev, buffer, length, ENTROPY_BUSYWAIT);
+}
+
+static int siwx917_init(const struct device *dev)
+{
+	int ret;
+
+	ret = RSI_CLK_PeripheralClkEnable1(M4CLK, HWRNG_PCLK_ENABLE);
+	if (ret) {
+		return -EIO;
+	}
+	ret = RSI_RNG_Start((void *)dev->config, RSI_RNG_TRUE_RANDOM);
+	if (ret) {
+		return -EIO;
+	}
+	return 0;
+}
+
+static const struct entropy_driver_api siwx917_api = {
+	.get_entropy = siwx917_get_entropy,
+	.get_entropy_isr = siwx917_get_entropy_isr,
+};
+
+#define SIWX917_RNG_INIT(idx)                                                               \
+	DEVICE_DT_INST_DEFINE(idx, siwx917_init, NULL, NULL, (void *)DT_INST_REG_ADDR(idx), \
+			      PRE_KERNEL_1, CONFIG_ENTROPY_INIT_PRIORITY, &siwx917_api);
+
+DT_INST_FOREACH_STATUS_OKAY(SIWX917_RNG_INIT)

dts/arm/silabs/siwg917.dtsi

@@ -9,6 +9,10 @@
 #include <zephyr/dt-bindings/spi/spi.h>
 
 / {
+	chosen {
+		zephyr,entropy = &rng0;
+	};
+
 	cpus {
 		#address-cells = <1>;
 		#size-cells = <0>;
@@ -202,6 +206,11 @@
 			interrupt-names = "i2c2";
 			status = "disabled";
 		};
+
+		rng0: rng@45090000 {
+			compatible = "silabs,siwx917-rng";
+			reg = <0x45090000 0x8>;
+		};
 	};
 };
 

dts/bindings/rng/silabs,siwx917-rng.yaml

@@ -0,0 +1,12 @@
+# Copyright (c) 2024 Silicon Laboratories Inc.
+# SPDX-License-Identifier: Apache-2.0
+
+description: Hardware Random Number Generator embedded on Silabs SiWx917 chips
+
+compatible: "silabs,siwx917-rng"
+
+include: base.yaml
+
+properties:
+  reg:
+    required: true

west.yml

@@ -11,7 +11,7 @@ manifest:
   projects:
     - name: hal_silabs
       remote: silabs
-      revision: 2eb82930b376900f1b6949e218199ab33ba6f34c
+      revision: ca720524a33c4bb55446ceb7e94502e37153d941
       path: modules/hal/silabs
     - name: zephyr
       remote: zephyrproject-rtos