pico-sdk: cybt: re-read transient corrupt ring index#17
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cybt_get_bt_buf_index() asserts when the BT controller's bt2host / host2bt ring indices read back out of range over the gSPI backplane. The gSPI bus is shared with WiFi, so under bus contention these indices can read corrupt for a single access, turning a recoverable glitch into a full system abort. Re-read the index up to CYBT_BUF_INDEX_REREAD_MAX (8) times and, if it still does not validate, return CYBT_ERR_HCI_READ_FAILED so the caller drops the cycle instead of aborting. Reproduced on a CYW43439 (Raspberry Pi Pico 2 W) under concurrent WiFi+BT load: the assert fired at boot and under sustained traffic; with the re-read the controller recovers and BT stays up across a 2-hour zero-fault WiFi+BLE coexistence soak. Mirrors the upstream pico-sdk fix (raspberrypi#3027) as an interim Zephyr-side carry until that merges and rolls up into hal_rpi_pico. Assisted-by: Claude Opus 4.8 <noreply@anthropic.com> Signed-off-by: Jonathan Beri <jmberi@gmail.com>
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Jul 5, 2026
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Please also update ChangeLog.zephyr.md.
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Mirrors the upstream pico-sdk fix raspberrypi#3027 into the
Zephyr
hal_rpi_picofork, so Zephyr users get it without waiting for apico-sdk roll-up.
Problem
cybt_get_bt_buf_index()reads the BT controller'shost2bt/bt2hostring indices over the gSPI backplane and
assert()s if any index is out ofrange. The gSPI bus is shared with WiFi traffic, so under bus contention a
single read can return a transiently corrupt value — and the assert then
turns a recoverable glitch into a full system abort.
Change
Re-read up to
CYBT_BUF_INDEX_REREAD_MAX(8) times — the corruption does notpersist — and only if it still does not validate return
CYBT_ERR_HCI_READ_FAILED, so the caller drops the cycle gracefully. Behaviouris unchanged on a valid read.
Testing
Reproduced on a CYW43439 (Raspberry Pi Pico 2 W) under concurrent WiFi+BT load:
the assert fired both at boot and under sustained traffic. With the re-read the
controller recovers and BT stays up across a 2-hour zero-fault WiFi+BLE
coexistence soak (
rpi_pico2/rp2350a/m33/w).Relates to RFC zephyrproject-rtos/zephyr#111811. Upstream: raspberrypi#3027.