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wch: do not re-arm the fallback ladder on link-partner loss

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The re-arm fixed F1 (FB_USB3_UP is terminal, so a replug into a USB2-only host
stayed dead) but introduced a worse regression, because the ladder advances on a
timer regardless of whether anything is attached.

Unplugged, nothing sets _fb_saw_terms, so the budget is 4 ticks of 0.55 s: at
~2.2 s training is declared exhausted and USB3 is torn down, and the 5th tick
at ~2.75 s runs ch56x_usb2_init() and latches FB_USB2_ACTIVE, which is itself
terminal. Any unplug longer than about three seconds therefore demoted the board
to 480 Mbps permanently - including the ordinary case of replugging into the
same SuperSpeed host, and this is the shipping default for hydrausb3_v1.

Re-arming safely requires gating the ladder on an attached partner rather than
on a timer, so F1 stays open. The rest of the state-owner work is unaffected:
fallback_enter() remains the only writer of _fb_state, fallback_timer_start()
still re-enables TMR0_IRQn (F10), and the deferred re-init still re-checks the
state after its settle (F7).
This commit is contained in:
hathach
2026-08-15 10:51:38 +07:00
parent d63a7716e1
commit 17858fa183
1 changed files with 9 additions and 7 deletions
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16
src/portable/wch/dcd_ch56x_usb30.c
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@ -630,14 +630,16 @@ static void handle_link_irq(uint8_t rhport) {
link_set_power_mode(2);
USBSS->LINK_CTRL |= USBSS_LINK_CTRL_POLLING_EN;
} else {
// partner disappeared: teardown now, settle + re-init deferred to task context
// partner disappeared: teardown now, settle + re-init deferred to task context.
//
// Deliberately does NOT re-arm the fallback ladder here. Doing so looks right - FB_USB3_UP
// is otherwise terminal, so a replug into a USB2-only host stays dead - but the ladder
// advances on a timer with no partner attached: unplugged, _fb_saw_terms is false, the
// 4-tick budget expires 2.2 s later and the 5th tick hands the port to USB2 for good
// (FB_USB2_ACTIVE is itself terminal). That demotes the ordinary case - unplug, replug into
// the same SuperSpeed host - to 480 Mbps permanently, which is worse than the case it
// fixes. Re-arming safely needs the ladder gated on an attached partner, not on a timer.
USBSS->LINK_INT_CTRL = 0;
#if CFG_TUD_WCH_USB30_FALLBACK
// Re-arm the ladder. FB_USB3_UP is otherwise terminal: usbd calls neither dcd_init nor
// dcd_connect on link loss, so a replug into a USB2-only host would find no ladder
// running and no USB2 controller (dcd_init deinit'd it) -- dead until a power cycle.
fallback_enter(FB_USB3_TRAINING);
#endif
dcd_event_t event = {.rhport = rhport, .event_id = DCD_EVENT_UNPLUGGED};
dcd_event_handler(&event, true);
usb30_bus_reset_from_isr();