Fix SDM detection for P4 (#972)

Author: bugadani

.cargo/config.toml

@@ -1,2 +1,3 @@
 [alias]
 xtask = "run --package xtask --"
+xrun = "run --package espflash --"

CHANGELOG.md

@@ -16,6 +16,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 
 - Corrected eFuse BLOCK0 definitions for ESP32-C2, ESP32-C3, and ESP32-S3 (#961)
+- Fixed Secure Download Mode detection on ESP32-P4 (#972)
 
 ### Removed
 

espflash/src/connection/mod.rs

@@ -87,7 +87,7 @@ impl SecurityInfo {
         ])
     }
 
-    fn security_flag_status(&self, flag_name: &str) -> bool {
+    pub(crate) fn security_flag_status(&self, flag_name: &str) -> bool {
         if let Some(&flag) = Self::security_flag_map().get(flag_name) {
             (self.flags & flag) != 0
         } else {

espflash/src/flasher/mod.rs

@@ -1253,7 +1253,13 @@ impl Flasher {
 
 #[cfg(feature = "serialport")]
 fn detect_sdm(connection: &mut Connection) {
-    if connection.read_reg(CHIP_DETECT_MAGIC_REG_ADDR).is_err() {
+    if let Ok(security_info) = connection.security_info(false) {
+        // Newer chips tell us if SDM is enabled.
+        connection.secure_download_mode =
+            security_info.security_flag_status("SECURE_DOWNLOAD_ENABLE");
+    } else if connection.read_reg(CHIP_DETECT_MAGIC_REG_ADDR).is_err() {
+        // On older chips, we have to guess by reading something. On these chips, there
+        // is always something readable at 0x40001000.
         log::warn!("Secure Download Mode is enabled on this chip");
         connection.secure_download_mode = true;
     }