entropy: rpi_pico: implement entropy driver for RP2350

Use get_rand_64() from Pico SDK for entropy.

Signed-off-by: Xudong Zheng <[email protected]>

Author: xudongzheng

boards/raspberrypi/rpi_pico2/rpi_pico2.dtsi

@@ -113,6 +113,10 @@ gpio0_lo: &gpio0 {
 	status = "okay";
 };
 
+&rng {
+	status = "okay";
+};
+
 zephyr_udc0: &usbd {
 	status = "okay";
 };

boards/raspberrypi/rpi_pico2/rpi_pico2_rp2350a_m33.yaml

@@ -12,6 +12,7 @@ supported:
   - clock
   - counter
   - dma
+  - entropy
   - gpio
   - hwinfo
   - i2c

drivers/entropy/CMakeLists.txt

@@ -34,6 +34,7 @@ zephyr_library_sources_ifdef(CONFIG_ENTROPY_NXP_ELE_TRNG        entropy_nxp_ele.
 zephyr_library_sources_ifdef(CONFIG_ENTROPY_NXP_ELS_TRNG        entropy_nxp_els_trng.c)
 zephyr_library_sources_ifdef(CONFIG_ENTROPY_PSA_CRYPTO_RNG      entropy_psa_crypto.c)
 zephyr_library_sources_ifdef(CONFIG_ENTROPY_RENESAS_RA          entropy_renesas_ra.c)
+zephyr_library_sources_ifdef(CONFIG_ENTROPY_RPI_PICO_RNG        entropy_rpi_pico.c)
 zephyr_library_sources_ifdef(CONFIG_ENTROPY_RV32M1_TRNG         entropy_rv32m1_trng.c)
 zephyr_library_sources_ifdef(CONFIG_ENTROPY_SAM_RNG             entropy_sam.c)
 zephyr_library_sources_ifdef(CONFIG_ENTROPY_SILABS_SIWX91X      entropy_silabs_siwx91x.c)

drivers/entropy/Kconfig

@@ -40,6 +40,7 @@ source "drivers/entropy/Kconfig.nrf_cracen"
 source "drivers/entropy/Kconfig.nxp"
 source "drivers/entropy/Kconfig.psa_crypto"
 source "drivers/entropy/Kconfig.renesas_ra"
+source "drivers/entropy/Kconfig.rpi_pico"
 source "drivers/entropy/Kconfig.rv32m1"
 source "drivers/entropy/Kconfig.sam"
 source "drivers/entropy/Kconfig.siwx91x"

drivers/entropy/Kconfig.rpi_pico

@@ -0,0 +1,14 @@
+# Raspberry Pi Pico entropy generator driver configuration
+
+# Copyright (c) 2024 Xudong Zheng
+# SPDX-License-Identifier: Apache-2.0
+
+config ENTROPY_RPI_PICO_RNG
+	bool "Raspberry Pi Pico entropy number generator driver"
+	default y
+	depends on DT_HAS_RASPBERRYPI_PICO_RNG_ENABLED
+	depends on SOC_SERIES_RP2350
+	select ENTROPY_HAS_DRIVER
+	select PICOSDK_USE_CLAIM
+	select PICOSDK_USE_RAND
+	select PICOSDK_USE_TIMER

drivers/entropy/entropy_rpi_pico.c

@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2024 Xudong Zheng
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <string.h>
+#include <pico/rand.h>
+#include <zephyr/drivers/entropy.h>
+#include <zephyr/spinlock.h>
+
+#define DT_DRV_COMPAT raspberrypi_pico_rng
+
+static struct k_spinlock entropy_lock;
+
+static int entropy_rpi_pico_get_entropy(const struct device *dev, uint8_t *buf, uint16_t len)
+{
+	__ASSERT_NO_MSG(buf != NULL);
+	uint8_t *buf_bytes = buf;
+
+	while (len > 0) {
+		uint64_t value;
+		size_t to_copy = MIN(sizeof(value), len);
+
+		K_SPINLOCK(&entropy_lock) {
+			value = get_rand_64();
+		}
+		memcpy(buf_bytes, &value, to_copy);
+		buf_bytes += to_copy;
+		len -= to_copy;
+	}
+
+	return 0;
+}
+
+static DEVICE_API(entropy, entropy_rpi_pico_api_funcs) = {
+	.get_entropy = entropy_rpi_pico_get_entropy
+};
+
+DEVICE_DT_INST_DEFINE(0,
+		    NULL, NULL, NULL, NULL,
+		    PRE_KERNEL_1, CONFIG_ENTROPY_INIT_PRIORITY,
+		    &entropy_rpi_pico_api_funcs);

dts/bindings/rng/raspberrypi,pico-rng.yaml

@@ -0,0 +1,8 @@
+# Copyright (c) 2024 Xudong Zheng
+# SPDX-License-Identifier: Apache-2.0
+
+description: Raspberry Pi Pico RNG/Entropy
+
+compatible: "raspberrypi,pico-rng"
+
+include: base.yaml

dts/vendor/raspberrypi/rpi_pico/rp2350.dtsi

@@ -21,6 +21,10 @@
 		die-temp0 = &die_temp;
 	};
 
+	chosen {
+		zephyr,entropy = &rng;
+	};
+
 	cpus {
 		#address-cells = <1>;
 		#size-cells = <0>;
@@ -453,6 +457,12 @@
 			interrupt-names = "irq0", "irq1";
 			status = "disabled";
 		};
+
+		rng: rng@400f0000 {
+			compatible = "raspberrypi,pico-rng";
+			reg = <0x400f0000 DT_SIZE_K(4)>;
+			status = "disabled";
+		};
 	};
 
 	pinctrl: pin-controller {

modules/hal_rpi_pico/CMakeLists.txt

@@ -157,6 +157,18 @@ if(CONFIG_HAS_RPI_PICO)
   zephyr_include_directories_ifdef(CONFIG_PICOSDK_USE_CLAIM
           ${common_dir}/hardware_claim/include)
 
+  zephyr_library_sources_ifdef(CONFIG_PICOSDK_USE_RAND
+    ${rp2_common_dir}/pico_rand/rand.c
+  )
+  zephyr_include_directories_ifdef(CONFIG_PICOSDK_USE_RAND
+    ${common_dir}/pico_sync/include
+    ${common_dir}/pico_time/include
+    ${rp2_common_dir}/pico_rand/include
+    ${rp2_common_dir}/pico_time_adapter/include
+    ${rp2_common_dir}/pico_unique_id/include
+  )
+  zephyr_linker_sources_ifdef(CONFIG_PICOSDK_USE_RAND DATA_SECTIONS uninit_data.ld)
+
   zephyr_include_directories_ifdef(CONFIG_RISCV
           ${common_dir}/pico_sync/include
           ${common_dir}/pico_time/include

modules/hal_rpi_pico/Kconfig

@@ -54,3 +54,8 @@ config PICOSDK_USE_RTC
 	bool
 	help
 	  Use the RTC driver from pico-sdk
+
+config PICOSDK_USE_RAND
+	bool
+	help
+	  Use the "rand" driver from pico-sdk