More comments

Author: will-v-pi

trustzone/hello_trustzone/CMakeLists.txt

@@ -6,18 +6,25 @@ target_link_libraries(hello_trustzone_s
         pico_secure
 )
 
+# Packaged no_flash binary
 pico_set_binary_type(hello_trustzone_s no_flash)
 pico_package_uf2_output(hello_trustzone_s 0x10000000)
 pico_add_extra_outputs(hello_trustzone_s)
 
 # Add non-secure executable
 add_executable(hello_trustzone_ns nonsecure.c)
-pico_set_uf2_family(hello_trustzone_ns "rp2350-arm-ns")
 target_link_libraries(hello_trustzone_ns
         pico_stdlib
 )
+
+# Set UF2 family manually
+pico_set_uf2_family(hello_trustzone_ns "rp2350-arm-ns")
+
+# Use stdio_usb
 pico_enable_stdio_uart(hello_trustzone_ns 0)
 pico_enable_stdio_usb(hello_trustzone_ns 1)
+
+# Default flash binary
 pico_add_extra_outputs(hello_trustzone_ns)
 
 # Set security options
@@ -29,7 +36,7 @@ pico_set_security_options(hello_trustzone_s hello_trustzone_ns
 # Set security ram split
 pico_set_security_ram_split(hello_trustzone_s hello_trustzone_ns SIMPLE 64k 2k)
 
-# Create combined UF2 (ns first)
+# Create combined UF2, for loading into the partition table (non-secure first)
 pico_concatenate_uf2_outputs(hello_trustzone hello_trustzone_ns hello_trustzone_s)
 
 
@@ -43,18 +50,24 @@ target_link_libraries(hello_trustzone_no_flash_s
         pico_secure
 )
 
+# no_flash binary for secure side
 pico_set_binary_type(hello_trustzone_no_flash_s no_flash)
 pico_add_extra_outputs(hello_trustzone_no_flash_s)
 
 # Add non-secure executable
 add_executable(hello_trustzone_no_flash_ns nonsecure.c)
-pico_set_uf2_family(hello_trustzone_no_flash_ns "rp2350-arm-ns")
 target_link_libraries(hello_trustzone_no_flash_ns
         pico_stdlib
 )
+
+# Set UF2 family manually
+pico_set_uf2_family(hello_trustzone_ns "rp2350-arm-ns")
+
+# Use stdio_usb
 pico_enable_stdio_uart(hello_trustzone_no_flash_ns 0)
 pico_enable_stdio_usb(hello_trustzone_no_flash_ns 1)
 
+# no_flash binary for non-secure side too
 pico_set_binary_type(hello_trustzone_no_flash_ns no_flash)
 pico_add_extra_outputs(hello_trustzone_no_flash_ns)
 
@@ -67,6 +80,6 @@ pico_set_security_options(hello_trustzone_no_flash_s hello_trustzone_no_flash_ns
 # Set security ram split (with NO_FLASH)
 pico_set_security_ram_split(hello_trustzone_no_flash_s hello_trustzone_no_flash_ns SIMPLE 64k 2k NO_FLASH)
 
-# Create combined CMake target
+# Create combined CMake target, for easy building
 add_custom_target(hello_trustzone_no_flash ALL
         DEPENDS hello_trustzone_no_flash_s hello_trustzone_no_flash_ns)

trustzone/hello_trustzone/nonsecure.c

@@ -14,6 +14,7 @@ int main() {
     // Request user IRQ from secure, which stdio_usb will use
     user_irq_request_unused_from_secure(1);
 
+    // Start stdio_usb
     stdio_usb_init();
 
     // Repeating timer

trustzone/hello_trustzone/secure.c

@@ -60,7 +60,7 @@ int main()
     rom_get_boot_info(&info);
     printf("Boot partition: %d\n", info.partition);
 
-    // Roll QMI to matching Non-Secure partition
+    // Roll QMI to matching Non-Secure partition, as Non-Secure runs from XIP
     int ns_partition = rom_get_owned_partition(info.partition);
     printf("Matching Non-Secure partition: %d\n", ns_partition);
     int rc = rom_roll_qmi_to_partition(ns_partition);