[libretiny] Fix LN882x boot crash with the logger or a uart on UART0 (#20162)

esphome/components/libretiny/core.cpp

@@ -1,6 +1,26 @@
 #ifdef USE_LIBRETINY
 
-// HAL functions live in hal.cpp. core.cpp is intentionally empty for
-// libretiny — there is no extra component bootstrap to keep here.
+// HAL functions live in hal.cpp; this file only holds the serial port
+// workaround below.
+
+#include "core.h"
+
+#ifdef USE_LN882X
+#include <sdk_private.h>
+
+// The SDK's open port handles (components/serial/serial.c); not in its header.
+extern "C" Serial_t *serial_handles[SER_PORT_NUM];
+
+namespace esphome::libretiny {
+
+void ensure_serial_handle(uint8_t port) {
+  if (port >= SER_PORT_NUM || serial_handles[port] != nullptr)
+    return;
+  // serial_init() zeroes and opens it; the port stays open for good.
+  serial_handles[port] = new Serial_t();
+}
+
+}  // namespace esphome::libretiny
+#endif  // USE_LN882X
 
 #endif  // USE_LIBRETINY

esphome/components/libretiny/core.h

@@ -4,6 +4,21 @@
 
 #include <Arduino.h>
 
-namespace esphome::libretiny {}  // namespace esphome::libretiny
+namespace esphome::libretiny {
+
+#ifdef USE_LN882X
+/// Give a hardware UART its SDK handle before its Serial begin()s.
+///
+/// LibreTiny's LN882H Serial passes the SDK's per port handle to
+/// serial_init(), which fills it in, but only the default log port (UART1)
+/// has one at boot. Any other port hands it NULL and the chip faults before
+/// setup, so a logger or uart on UART0 never boots. Drop this once LibreTiny
+/// gives each port storage of its own.
+void ensure_serial_handle(uint8_t port);
+#else
+inline void ensure_serial_handle(uint8_t /*port*/) {}
+#endif
+
+}  // namespace esphome::libretiny
 
 #endif  // USE_LIBRETINY

esphome/components/logger/logger_libretiny.cpp

@@ -1,6 +1,8 @@
 #ifdef USE_LIBRETINY
 #include "logger.h"
 
+#include "esphome/components/libretiny/core.h"
+
 namespace esphome::logger {
 
 static const char *const TAG = "logger";
@@ -11,18 +13,21 @@ void Logger::pre_setup() {
 #if LT_HW_UART0
       case UART_SELECTION_UART0:
         this->hw_serial_ = &Serial0;
+        libretiny::ensure_serial_handle(0);
         Serial0.begin(this->baud_rate_);
         break;
 #endif
 #if LT_HW_UART1
       case UART_SELECTION_UART1:
         this->hw_serial_ = &Serial1;
+        libretiny::ensure_serial_handle(1);
         Serial1.begin(this->baud_rate_);
         break;
 #endif
 #if LT_HW_UART2
       case UART_SELECTION_UART2:
         this->hw_serial_ = &Serial2;
+        libretiny::ensure_serial_handle(2);
         Serial2.begin(this->baud_rate_);
         break;
 #endif

esphome/components/uart/uart_component_libretiny.cpp

@@ -6,6 +6,8 @@
 #include "esphome/core/log.h"
 #include "uart_component_libretiny.h"
 
+#include "esphome/components/libretiny/core.h"
+
 #ifdef USE_LOGGER
 #include "esphome/components/logger/logger.h"
 #endif
@@ -118,6 +120,8 @@ void LibreTinyUARTComponent::setup() {
 #endif
   }
 
+  if (this->hardware_idx_ >= 0)
+    libretiny::ensure_serial_handle(this->hardware_idx_);
   this->serial_->begin(this->baud_rate_, get_config());
 }
 

tests/components/logger/test-uart0.ln882x-ard.yaml

@@ -0,0 +1,2 @@
+logger:
+  hardware_uart: UART0

tests/components/uart/test.ln882x-ard.yaml

@@ -0,0 +1,14 @@
+uart:
+  - id: uart_id
+    tx_pin: PA2
+    rx_pin: PA3
+    baud_rate: 9600
+    data_bits: 8
+    parity: NONE
+    stop_bits: 1
+
+switch:
+  - platform: uart
+    name: "UART Switch"
+    uart_id: uart_id
+    data: [0x01, 0x02, 0x03]