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libretiny: grow BK72xx .itcm region from 4.5 kB to 8.5 kB

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The SDK's built-in ISR / flash / FreeRTOS critical-path code already fills
most of the stock 4.5 kB .itcm executable RAM region, leaving under 500
bytes for ESPHome's IRAM_ATTR functions. cb3s overflowed by 248 bytes on
first link. Physically .tcm (rw!x, data) and .itcm (rwx, code) are
contiguous SRAM blocks on ARM968E-S; the template's boundary is just a
linker carve-out. Shift it back 4 kB so .tcm shrinks 60k -> 56k and .itcm
grows 4.5k -> 8.5k. Confirmed fits every ESPHome IRAM_ATTR function on cb3s
with ample headroom.
This commit is contained in:
J. Nick Koston
2026-04-15 14:24:57 -10:00
parent 365ff86bac
commit 85d1ab7303
1 changed files with 23 additions and 4 deletions
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esphome/components/libretiny/patch_linker.py.script
+23 -4
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@@ -38,6 +38,25 @@ _BK_ITCM = re.compile(r"(\.itcm\.code\s*ALIGN\s*\(\s*\d+\s*\)\s*:\s*\{\s*\n)")
_LN_COPY = re.compile(r"(\.flash_copysection\s*:\s*\{\s*\n)")
_RTL8710B_IMAGE2 = re.compile(r"(\.image2\.ram\.text\s*:\s*\{\s*\n)")
# On BK72xx the stock LibreTiny linker carves a 4.5 kB ".itcm" executable RAM
# region; the SDK already fills most of it with its own ISR / flash / FreeRTOS
# critical code, leaving <500 bytes for ESPHome IRAM_ATTR functions. Steal 4 kB
# from the adjacent (rw!x) "tcm" data region and give it to itcm so our
# .sram.text payload has room to grow. Physically tcm and itcm are contiguous
# SRAM, so shifting the boundary is just a linker rewrite.
_BK_TCM_LEN = re.compile(r"(\btcm\s*\(\s*rw!x\s*\)\s*:\s*ORIGIN\s*=\s*0x003F0000\s*,\s*LENGTH\s*=\s*)60k(\s*-\s*512\b)")
_BK_ITCM_REGION = re.compile(
r"(\bitcm\s*\(\s*rwx\s*\)\s*:\s*ORIGIN\s*=\s*)0x003FEE00(\s*,\s*LENGTH\s*=\s*)4k(\s*\+\s*512\b)"
)
def _grow_bk72xx_itcm(content):
# Shrink tcm by 4 kB: 60k - 512 -> 56k - 512.
new_content = _BK_TCM_LEN.sub(r"\g<1>56k\g<2>", content)
# Shift itcm origin back 4 kB and grow length: 4k + 512 -> 8k + 512.
new_content = _BK_ITCM_REGION.sub(r"\g<1>0x003FDE00\g<2>8k\g<3>", new_content)
return new_content
def _detect(env):
prefix = "USE_LIBRETINY_VARIANT_"
@@ -80,10 +99,10 @@ def _inject_keep(host_section):
# RTL8720C is absent: its stock linker already consumes *(.sram.text*), so
# no .ld patch is needed; the summary falls back to reading symbol addresses.
_PATCHERS_BY_VARIANT = {
"BK7231N": (_inject_keep(_BK_ITCM),),
"BK7231T": (_inject_keep(_BK_ITCM),),
"BK7231Q": (_inject_keep(_BK_ITCM),),
"BK7251": (_inject_keep(_BK_ITCM),),
"BK7231N": (_grow_bk72xx_itcm, _inject_keep(_BK_ITCM)),
"BK7231T": (_grow_bk72xx_itcm, _inject_keep(_BK_ITCM)),
"BK7231Q": (_grow_bk72xx_itcm, _inject_keep(_BK_ITCM)),
"BK7251": (_grow_bk72xx_itcm, _inject_keep(_BK_ITCM)),
"LN882H": (_inject_keep(_LN_COPY),),
"RTL8710B": (_inject_keep(_RTL8710B_IMAGE2),),
}