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LCD-7: a 64 KB data cache as well #20

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Merged
bdbarnett merged 1 commit into from
Sep 25, 2026
Merged

LCD-7: a 64 KB data cache as well #20

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21 changes: 16 additions & 5 deletions boards/esp32/WAVESHARE_ESP32_S3_TOUCH_LCD_7/sdkconfig.lcd7
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
# Waveshare ESP32-S3-Touch-LCD-7, on top of the 4.3" board's sdkconfig.board.
# Measured 2026-09-25 with spotapi's remote on the panel and earful streaming
# Spotify into a USB sound card hosted on the native port (earful
# docs/lcd-7.md).
# Measured 2026-09-25 with an LVGL remote-control UI on the panel and a
# Spotify Connect speaker streaming into a USB sound card hosted on the
# native port.
#
# Internal DMA-capable RAM is what runs out first on this board: the panel's
# bounce buffers, the Wi-Fi driver, hardware AES and the USB host all need
Expand Down Expand Up @@ -33,7 +33,18 @@ CONFIG_FREERTOS_HZ=1000
# LVGL call ran 5-10x slower than its code. Measured on the remote's UI
# (2026-09-25): 64-byte lines took a full-screen redraw from 176 to 146 ms;
# a 32 KB instruction cache then took a list row from 66 to 44 ms and the
# redraw to 117 ms. It costs 16 KB of internal RAM (DMA-capable free 64 ->
# 48 KB). A 64 KB data cache (rows 30 ms) would leave ~13 KB, too little.
# redraw to 117 ms.
#
# A 64 KB data cache on top, measured while the board also decodes and
# streams audio: full redraw 205 -> 147 ms, panel switch 88 -> 59 ms, 30
# list rows built 780 -> 399 ms and laid out 608 -> 335 ms. The same layout
# runs ~216x faster on a desktop, so this board is memory-bound, and the
# data cache is the lever. Together the caches take 48 KB of internal RAM:
# free internal went 54 -> 23 KB. Soaked 30 min of real use (about 25 skips
# and track picks, Wi-Fi streaming and a USB host running): the minimum
# stayed at 17 KB, with no allocation failures, Wi-Fi drops or audio
# stalls. (The 24-byte failure above came from every malloc under 8 KB
# landing in internal RAM; ALWAYSINTERNAL=512 sends those to PSRAM now.)
CONFIG_ESP32S3_DATA_CACHE_LINE_64B=y
CONFIG_ESP32S3_INSTRUCTION_CACHE_32KB=y
CONFIG_ESP32S3_DATA_CACHE_64KB=y