CMake that generates the Picotool flash unique ID access payload

CMakeLists.txt

cmake_minimum_required(VERSION 3.20)

# default build type
set(CMAKE_BUILD_TYPE "MinSizeRel" CACHE STRING "build type")

include(pico_sdk_import.cmake)
project(flash_id C CXX ASM)
pico_sdk_init()

add_executable(flash_id flash_id.c)
target_link_libraries(flash_id PRIVATE
    hardware_regs hardware_structs hardware_flash_headers
)
target_link_options(flash_id PRIVATE -nostartfiles -nodefaultlibs -Ttext=0)
pico_add_bin_output(flash_id)

flash_id.c

#include "hardware/regs/io_qspi.h"
#include "hardware/structs/ioqspi.h"
#include "hardware/structs/ssi.h"
#include "hardware/flash.h"

asm(
    ".macro static_assert value, msg\n"
        ".if !(\\value)\n"
        ".err \\msg\n"
        ".endif\n"
    ".endm\n"

    ".set FLASH_RUID_CMD, 0x4b\n"
    ".set FLASH_RUID_DUMMY_BYTES, 4\n"
    ".set FLASH_RUID_DATA_BYTES, 8\n"
    ".set FLASH_RUID_TOTAL_BYTES, (1 + FLASH_RUID_DUMMY_BYTES + FLASH_RUID_DATA_BYTES)\n"
);

void flash_do_cmd(const uint8_t * txbuf, uint8_t *rxbuf, size_t count);
void __attribute__((naked)) flash_get_unique_id_raw(void) {
    asm(
        ".Lflash_get_unique_id_raw:\n"
            "adr r0, .Ltxbuf\n"
            "adr r1, .Lrxbuf\n"
            "ldr r2, .Lbuflen\n"
            "b flash_do_cmd\n"
        ".Lbuflen:\n"
            ".word FLASH_RUID_TOTAL_BYTES\n"
        ".Ltxbuf:\n"
            ".byte FLASH_RUID_CMD\n"
            ".zero (FLASH_RUID_TOTAL_BYTES - 1)\n"
            ".zero (16 - FLASH_RUID_TOTAL_BYTES)\n"
        ".Lrxbuf:\n"
            ".zero FLASH_RUID_TOTAL_BYTES\n"
            ".zero (16 - FLASH_RUID_TOTAL_BYTES)\n"
        "static_assert ((.Lrxbuf - flash_get_unique_id_raw) == 28), \"rxbuf offset incorrect\"\n"
    );
}

static inline void __attribute__((always_inline)) flash_cs_force(_Bool high) {
    uint32_t field_val = high ?
        IO_QSPI_GPIO_QSPI_SS_CTRL_OUTOVER_VALUE_HIGH :
        IO_QSPI_GPIO_QSPI_SS_CTRL_OUTOVER_VALUE_LOW;
    hw_write_masked(&ioqspi_hw->io[1].ctrl,
        field_val << IO_QSPI_GPIO_QSPI_SS_CTRL_OUTOVER_LSB,
        IO_QSPI_GPIO_QSPI_SS_CTRL_OUTOVER_BITS
    );
}

void flash_do_cmd(const uint8_t * txbuf, uint8_t *rxbuf, size_t count) {
    flash_cs_force(0);
    size_t tx_remaining = count;
    size_t rx_remaining = count;
    // We may be interrupted -- don't want FIFO to overflow if we're distracted.
    const size_t max_in_flight = 16 - 2;
    while (tx_remaining || rx_remaining) {
        uint32_t flags = ssi_hw->sr;
        bool can_put = !!(flags & SSI_SR_TFNF_BITS);
        bool can_get = !!(flags & SSI_SR_RFNE_BITS);
        if (can_put && tx_remaining && rx_remaining - tx_remaining < max_in_flight) {
            ssi_hw->dr0 = *txbuf++;
            --tx_remaining;
        }
        if (can_get && rx_remaining) {
            *rxbuf++ = (uint8_t)ssi_hw->dr0;
            --rx_remaining;
        }
    }
    flash_cs_force(1);
}

pico_sdk_import.cmake

# This is a copy of <PICO_SDK_PATH>/external/pico_sdk_import.cmake

# This can be dropped into an external project to help locate this SDK
# It should be include()ed prior to project()

if (DEFINED ENV{PICO_SDK_PATH} AND (NOT PICO_SDK_PATH))
    set(PICO_SDK_PATH $ENV{PICO_SDK_PATH})
    message("Using PICO_SDK_PATH from environment ('${PICO_SDK_PATH}')")
endif ()

if (DEFINED ENV{PICO_SDK_FETCH_FROM_GIT} AND (NOT PICO_SDK_FETCH_FROM_GIT))
    set(PICO_SDK_FETCH_FROM_GIT $ENV{PICO_SDK_FETCH_FROM_GIT})
    message("Using PICO_SDK_FETCH_FROM_GIT from environment ('${PICO_SDK_FETCH_FROM_GIT}')")
endif ()

if (DEFINED ENV{PICO_SDK_FETCH_FROM_GIT_PATH} AND (NOT PICO_SDK_FETCH_FROM_GIT_PATH))
    set(PICO_SDK_FETCH_FROM_GIT_PATH $ENV{PICO_SDK_FETCH_FROM_GIT_PATH})
    message("Using PICO_SDK_FETCH_FROM_GIT_PATH from environment ('${PICO_SDK_FETCH_FROM_GIT_PATH}')")
endif ()

if (DEFINED ENV{PICO_SDK_FETCH_FROM_GIT_TAG} AND (NOT PICO_SDK_FETCH_FROM_GIT_TAG))
    set(PICO_SDK_FETCH_FROM_GIT_TAG $ENV{PICO_SDK_FETCH_FROM_GIT_TAG})
    message("Using PICO_SDK_FETCH_FROM_GIT_TAG from environment ('${PICO_SDK_FETCH_FROM_GIT_TAG}')")
endif ()

if (PICO_SDK_FETCH_FROM_GIT AND NOT PICO_SDK_FETCH_FROM_GIT_TAG)
  set(PICO_SDK_FETCH_FROM_GIT_TAG "master")
  message("Using master as default value for PICO_SDK_FETCH_FROM_GIT_TAG")
endif()

set(PICO_SDK_PATH "${PICO_SDK_PATH}" CACHE PATH "Path to the Raspberry Pi Pico SDK")
set(PICO_SDK_FETCH_FROM_GIT "${PICO_SDK_FETCH_FROM_GIT}" CACHE BOOL "Set to ON to fetch copy of SDK from git if not otherwise locatable")
set(PICO_SDK_FETCH_FROM_GIT_PATH "${PICO_SDK_FETCH_FROM_GIT_PATH}" CACHE FILEPATH "location to download SDK")
set(PICO_SDK_FETCH_FROM_GIT_TAG "${PICO_SDK_FETCH_FROM_GIT_TAG}" CACHE FILEPATH "release tag for SDK")

if (NOT PICO_SDK_PATH)
    if (PICO_SDK_FETCH_FROM_GIT)
        include(FetchContent)
        set(FETCHCONTENT_BASE_DIR_SAVE ${FETCHCONTENT_BASE_DIR})
        if (PICO_SDK_FETCH_FROM_GIT_PATH)
            get_filename_component(FETCHCONTENT_BASE_DIR "${PICO_SDK_FETCH_FROM_GIT_PATH}" REALPATH BASE_DIR "${CMAKE_SOURCE_DIR}")
        endif ()
        # GIT_SUBMODULES_RECURSE was added in 3.17
        if (${CMAKE_VERSION} VERSION_GREATER_EQUAL "3.17.0")
            FetchContent_Declare(
                    pico_sdk
                    GIT_REPOSITORY https://github.com/raspberrypi/pico-sdk
                    GIT_TAG ${PICO_SDK_FETCH_FROM_GIT_TAG}
                    GIT_SUBMODULES_RECURSE FALSE
            )
        else ()
            FetchContent_Declare(
                    pico_sdk
                    GIT_REPOSITORY https://github.com/raspberrypi/pico-sdk
                    GIT_TAG ${PICO_SDK_FETCH_FROM_GIT_TAG}
            )
        endif ()

        if (NOT pico_sdk)
            message("Downloading Raspberry Pi Pico SDK")
            FetchContent_Populate(pico_sdk)
            set(PICO_SDK_PATH ${pico_sdk_SOURCE_DIR})
        endif ()
        set(FETCHCONTENT_BASE_DIR ${FETCHCONTENT_BASE_DIR_SAVE})
    else ()
        message(FATAL_ERROR
                "SDK location was not specified. Please set PICO_SDK_PATH or set PICO_SDK_FETCH_FROM_GIT to on to fetch from git."
                )
    endif ()
endif ()

get_filename_component(PICO_SDK_PATH "${PICO_SDK_PATH}" REALPATH BASE_DIR "${CMAKE_BINARY_DIR}")
if (NOT EXISTS ${PICO_SDK_PATH})
    message(FATAL_ERROR "Directory '${PICO_SDK_PATH}' not found")
endif ()

set(PICO_SDK_INIT_CMAKE_FILE ${PICO_SDK_PATH}/pico_sdk_init.cmake)
if (NOT EXISTS ${PICO_SDK_INIT_CMAKE_FILE})
    message(FATAL_ERROR "Directory '${PICO_SDK_PATH}' does not appear to contain the Raspberry Pi Pico SDK")
endif ()

set(PICO_SDK_PATH ${PICO_SDK_PATH} CACHE PATH "Path to the Raspberry Pi Pico SDK" FORCE)

include(${PICO_SDK_INIT_CMAKE_FILE})