drivers: hwinfo: rpi_pico: use bootrom method on RP2350

RP2350 provides a function to get OTP-backed chip ID. Prefer using this
on supported platforms for these reasons:
- a secure internal identifier, same as read by picotool
- works on flashless boards
- does not conflict with code running in XIP mode (e.g. when the other
 core tries to access device ID)
- when used with USB HWID serial number will match one BootROM has

Signed-off-by: Dmitrii Sharshakov <[email protected]>
Co-authored-by: Alexander Wachter <[email protected]>

Author: 2 people

drivers/hwinfo/Kconfig

@@ -152,6 +152,18 @@ config HWINFO_RPI_PICO
 	help
 	  Enable Raspberry Pi Pico hwinfo driver.
 
+config HWINFO_RPI_PICO_CHIP_ID
+	bool "Use chip ID as device ID for RP2350"
+	default n
+	depends on SOC_SERIES_RP2350
+	depends on HWINFO_RPI_PICO
+	help
+	  Use the chip ID as device ID for RP2350 instead of the default
+	  flash RUID. This is useful for RP2350 boards that do not have a
+	  flash, or when OTP ID is preferred over flash RUID.
+	  This option is recommended for new RP2350 designs, but defaults to n
+	  to prevent existing devices from changing their serial numbers.
+
 config HWINFO_SAM_RSTC
 	bool "Atmel SAM reset cause"
 	default y

drivers/hwinfo/hwinfo_rpi_pico.c

@@ -11,6 +11,8 @@
 #if defined(CONFIG_SOC_SERIES_RP2040)
 #include <hardware/structs/vreg_and_chip_reset.h>
 #else
+#include <zephyr/sys/byteorder.h>
+#include <pico/bootrom.h>
 #include <hardware/structs/powman.h>
 #endif
 
@@ -29,6 +31,20 @@
 ssize_t z_impl_hwinfo_get_device_id(uint8_t *buffer, size_t length)
 {
 	uint8_t id[FLASH_RUID_DATA_BYTES];
+
+#if CONFIG_HWINFO_RPI_PICO_CHIP_ID
+	rom_get_sys_info_fn get_sys_info = (rom_get_sys_info_fn)
+					rom_func_lookup_inline(ROM_FUNC_GET_SYS_INFO);
+	/* Words: CHIP_INFO, PACKAGE_SEL, DEVICE_ID, WAFER_ID */
+	uint32_t words[4];
+
+	int n = get_sys_info(words, ARRAY_SIZE(words), SYS_INFO_CHIP_INFO);
+	/* CHIP_INFO returns 4 words */
+	__ASSERT(n == ARRAY_SIZE(words), "Failed to get chip info");
+
+	/* Use DEVICE_ID + WAFER_ID, like BootROM uses for its USB ID */
+	sys_put_be(id, &words[2], 2 * sizeof(uint32_t));
+#else
 	uint32_t key;
 
 	/*
@@ -40,6 +56,7 @@ ssize_t z_impl_hwinfo_get_device_id(uint8_t *buffer, size_t length)
 	key = irq_lock();
 	flash_get_unique_id(id);
 	irq_unlock(key);
+#endif /* defined(CONFIG_SOC_SERIES_RP2350) */
 
 	if (length > sizeof(id)) {
 		length = sizeof(id);