Ben Meadors e2460b546e MUI: stop holding the SPI bus across the whole UI cycle (#11278) ...

tft_task_handler held spiLock for the entire LVGL cycle. Most of that
cycle is timer work and rendering into the draw buffer, which issues no
SPI at all - but on boards where the TFT, SD card and LoRa radio share
one bus (T-Deck), every radio operation on the main loop still waited it
out. That is tens to hundreds of milliseconds whenever the UI animates,
felt as mesh RX/TX latency.

device-ui now takes the lock around its own transfers instead
(meshtastic/device-ui#356), so the coarse hold here can go and the bus is
contended only during real traffic.

Lend it spiLock through a reentrant adapter. device-ui nests its guards -
SdFsCard::usedBytes() calls cardSize() and freeBytes(), each of which
takes the lock - while spiLock is a plain binary semaphore that would
self-deadlock on the second take, so track the owning task and only touch
the underlying lock on the outermost acquire.

Requires the device-ui pin bump included here.

Tested on T-Deck: flush, touch, panel init, SD detect, powersave sleep
and wake all exercised; LoRa RX decoding under a live UI, no deadlocks,
no watchdog resets. Also builds seeed-sensecap-indicator-tft.

Co-authored-by: Manuel <71137295+mverch67@users.noreply.github.com>

2026-07-31 10:49:39 +00:00

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