tcl/esp_common: fix incorrect sampling of ESP32 bootstrap pin GPIO12

tcl/target/esp_common.cfg

@@ -396,6 +396,8 @@ proc esp_gcov_dump {} {
 # special function to program ESP chip, it differs from the original 'program' that
 # it verifies written image by reading flash directly, instead of reading memory mapped flash regions
 proc program_esp {filename args} {
+	global _FLASH_VOLTAGE
+
 	set exit 0
 	set compress 0
 	set clock_boost 1
@@ -443,6 +445,28 @@ proc program_esp {filename args} {
 		program_error "** OpenOCD init failed **" 1
 	}
 
+	if { [info exists _FLASH_VOLTAGE] } {
+		foreach tgt [target names] {
+			set state [$tgt curstate]
+			if {$state eq "running"} {
+				# When the flash is empty, the TDI pin remains floating and may be sampled at an incorrect level by the
+				# bootstrap circuit. This can cause the flash to operate at an unexpected voltage.
+				# To address this, we ensure the TDI pin is set to the correct level before re-sampling the bootstrap
+				# registers. OpenOCD will poll once to adjust the TDI level and then wait for the target to undergo a
+				# WDT reset, which triggers re-sampling of the bootstrap pin.
+				# The observed interval between two WDT resets is approximately 350ms.
+				# This workaround is applied while the target is running because a WDT reset is the only way
+				# to force the target to re-sample the bootstrap pin.
+				# Additionally, if the flash is empty, the CPU will not be able to load firmware, which guarantees that
+				# the watchdog timer will be triggerred continuously, causing resets
+				# until the firmware is properly loaded.
+				poll
+				sleep 350
+				break
+			}
+		}
+	}
+
 	# reset target and call any init scripts
 	if {[catch {reset init}] != 0} {
 		program_error "** Unable to reset target **" $exit