libretiny: clean up stale comments and tighten patch_linker script

- hal.h: collapse the four-way USE_LIBRETINY_VARIANT_BK72* guard into
  USE_BK72XX.
- libretiny/__init__.py: drop the stale reference to growing .itcm from
  4.5 kB to 8.5 kB; BK72xx no longer gets any .ld patching.
- patch_linker.py.script: hoist the duplicated "import subprocess" to the
  top, pull the fallback IRAM_ATTR symbols out into a module-level
  frozenset, and split the ELF scan into a helper so _post_link is just
  the print logic.

esphome/components/libretiny/__init__.py

@@ -468,16 +468,14 @@ async def component_to_code(config):
         build_src_flags += " -Os"
     cg.add_platformio_option("build_src_flags", build_src_flags)
     # IRAM_ATTR on LibreTiny expands to section(".sram.text") on families
-    # where executable RAM is available (see esphome/core/hal.h). This pre-
-    # link hook rewrites the processed .ld files in the build dir so that
-    # section lands in each family's executable RAM output section:
-    #   - BK7231N: grow .itcm from 4.5 kB to 8.5 kB (steal from .tcm) and
-    #     inject KEEP(*(.sram.text*)) into .itcm.code.
+    # where the ISR-during-flash race is real (see esphome/core/hal.h). This
+    # pre-link hook routes that section into each family's executable RAM:
     #   - LN882H: inject KEEP(*(.sram.text*)) into .flash_copysection.
     #   - RTL8710B: inject KEEP(*(.sram.text*)) into .image2.ram.text.
     #   - RTL8720C: no-op (stock linker already consumes *(.sram.text*)).
-    # BK7231T/Q/7251 have no executable RAM region; their SDK disables IRQ
-    # + FIQ around flash writes, so IRAM_ATTR is left a no-op on them.
+    # BK72xx (all variants) is no-op: the Beken SDK wraps every flash write
+    # in GLOBAL_INT_DISABLE() so no ISR can fire during a flash stall; the
+    # race IRAM_ATTR guards against cannot occur.
     cg.add_platformio_option("extra_scripts", ["pre:patch_linker.py"])
     # dummy version code
     cg.add_define("USE_ARDUINO_VERSION_CODE", cg.RawExpression("VERSION_CODE(0, 0, 0)"))

esphome/components/libretiny/patch_linker.py.script

@@ -3,6 +3,7 @@ Import("env")  # noqa
 
 import os
 import re
+import subprocess
 
 # ESPHome marks ISR code IRAM_ATTR, which on LibreTiny expands to
 # section(".sram.text") (see esphome/core/hal.h). Each family's linker script
@@ -122,46 +123,50 @@ def _pre_link(target, source, env):
     _patch_build_dir(_patchers, env.subst("$BUILD_DIR"))
 
 
-def _post_link(target, source, env):
-    """Print where IRAM_ATTR ended up so users can confirm at a glance."""
-    nm = env.subst("$NM") or "arm-none-eabi-nm"
-    elf = env.subst("$BUILD_DIR/${PROGNAME}.elf")
-    if not os.path.isfile(elf):
-        return
+# Well-known ESPHome IRAM_ATTR symbols used as a fallback on RTL8720C, where
+# we cannot inject the __esphome_sram_text_start/end markers.
+_FALLBACK_IRAM_SYMBOLS = frozenset({
+    "_ZN7esphome21wake_loop_any_contextEv",
+    "_ZN7esphome17wake_loop_isrsafeEPl",
+    "_ZN7esphome9Component28enable_loop_soon_any_contextEv",
+})
+
+
+def _collect_iram_symbols(nm, elf):
+    """Return (start, end, fallback_addresses) for the IRAM_ATTR payload."""
     try:
-        import subprocess
         out = subprocess.check_output([nm, "--defined-only", elf], text=True)
     except (OSError, subprocess.CalledProcessError):
-        return
+        return None, None, []
     start = end = None
-    sample = []
+    fallback = []
     for line in out.splitlines():
         parts = line.split(maxsplit=2)
         if len(parts) != 3:
             continue
-        addr, _kind, name = parts
+        addr_str, _kind, name = parts
         if name == "__esphome_sram_text_start":
-            start = int(addr, 16)
+            start = int(addr_str, 16)
         elif name == "__esphome_sram_text_end":
-            end = int(addr, 16)
-        elif name in (
-            "_ZN7esphome21wake_loop_any_contextEv",
-            "_ZN7esphome17wake_loop_isrsafeEPl",
-            "_ZN7esphome9Component28enable_loop_soon_any_contextEv",
-        ):
-            sample.append((int(addr, 16), name))
-    header = "ESPHome: IRAM_ATTR placement summary ({}):".format(_variant)
+            end = int(addr_str, 16)
+        elif name in _FALLBACK_IRAM_SYMBOLS:
+            fallback.append(int(addr_str, 16))
+    return start, end, fallback
+
+
+def _post_link(target, source, env):
+    """Print where IRAM_ATTR ended up so users can confirm at a glance."""
+    elf = env.subst("$BUILD_DIR/${PROGNAME}.elf")
+    if not os.path.isfile(elf):
+        return
+    start, end, fallback = _collect_iram_symbols(env.subst("$NM"), elf)
+    print("ESPHome: IRAM_ATTR placement summary ({}):".format(_variant))
     if start is not None and end is not None:
-        print(header)
         print("  .sram.text:  {} bytes at 0x{:08x} - 0x{:08x}".format(end - start, start, end))
-    elif sample:
-        print(header)
-        sample.sort()
-        lo = sample[0][0]
-        hi = sample[-1][0]
+    elif fallback:
+        lo, hi = min(fallback), max(fallback)
         print("  IRAM symbols at 0x{:08x} - 0x{:08x} (approx {} bytes)".format(lo, hi, hi - lo))
     else:
-        print(header)
         print("  no IRAM_ATTR symbols found in the ELF")
 
 

esphome/core/hal.h

@@ -56,10 +56,11 @@
 #include <freertos/task.h>
 #endif
 
-#if defined(USE_LIBRETINY_VARIANT_BK7231N) || defined(USE_LIBRETINY_VARIANT_BK7231T) || \
-    defined(USE_LIBRETINY_VARIANT_BK7231Q) || defined(USE_LIBRETINY_VARIANT_BK7251)
+#ifdef USE_BK72XX
 // Declared in the Beken FreeRTOS port (portmacro.h) and built in ARM mode so
-// it is callable from Thumb code via interworking.
+// it is callable from Thumb code via interworking. The MRS CPSR instruction
+// is ARM-only and user code here may be built in Thumb, so in_isr_context()
+// defers to this port helper on BK72xx instead of reading CPSR inline.
 extern "C" uint32_t platform_is_in_interrupt_context(void);
 #endif
 
@@ -79,11 +80,8 @@ __attribute__((always_inline)) inline bool in_isr_context() {
   uint32_t ipsr;
   __asm__ volatile("mrs %0, ipsr" : "=r"(ipsr));
   return ipsr != 0;
-#elif defined(USE_LIBRETINY_VARIANT_BK7231N) || defined(USE_LIBRETINY_VARIANT_BK7231T) || \
-    defined(USE_LIBRETINY_VARIANT_BK7231Q) || defined(USE_LIBRETINY_VARIANT_BK7251)
-  // BK72xx is ARM968E-S (ARM9). The MRS CPSR instruction is ARM-only, and
-  // user code here may be built in Thumb mode. Defer to the FreeRTOS port
-  // helper declared above (compiled in ARM mode by the SDK).
+#elif defined(USE_BK72XX)
+  // BK72xx is ARM968E-S (ARM9); see extern declaration above.
   return platform_is_in_interrupt_context() != 0;
 #elif defined(USE_LIBRETINY)
   // Cortex-M (AmebaZ, AmebaZ2, LN882H). IPSR is the active exception number;