shared/tinyusb: Implement tusb_time_delay_ms_api using mp_hal_delay_ms.#19213
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shared/tinyusb: Implement tusb_time_delay_ms_api using mp_hal_delay_ms.#19213andrewleech wants to merge 1 commit into
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TinyUSB declares tusb_time_delay_ms_api() as a weak function, defaulting to a busy-wait loop via tusb_time_millis_api(). Provide an implementation using mp_hal_delay_ms() to avoid the busy-wait. This is required by the dwc2 synopsys driver for STM32 boards with an internal USB HS PHY (USB_HS_PHYC), which calls tusb_time_delay_ms_api() to wait 2ms for the PHYC PLL to stabilise during init. Signed-off-by: Andrew Leech <andrew.leech@planetinnovation.com.au>
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dpgeorge
reviewed
May 12, 2026
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| // Required by TinyUSB drivers that need a blocking delay (e.g. dwc2 USB_HS_PHYC PLL init). | ||
| void tusb_time_delay_ms_api(uint32_t ms) { | ||
| mp_hal_delay_ms(ms); |
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Not sure this is the right thing to do. This pumps the event loop and may raise an exception.
Really it wants to call something like HAL_Delay(), but that's only available on stm32. So maybe this function needs to be implemented per port?
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Code size report: |
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Summary
Found while testing #19201: PYBD_SF3 fails to link with TinyUSB enabled, with an undefined reference to
tusb_time_millis_api. The root cause (identified by @dpgeorge) is thattusb_time_delay_ms_api()- a weak function in TinyUSB whose default implementation busy-loops ontusb_time_millis_api()- gets pulled into the binary on boards with an internal USB HS PHY (USB_HS_PHYC). The dwc2 driver calls it to wait 2ms for the PHYC PLL to stabilise during init, and PYBD_SF3 (STM32F722) is currently the only MicroPython board where this code path is reached.Rather than implementing
tusb_time_millis_api()and keeping the busy-wait, this overridestusb_time_delay_ms_api()directly usingmp_hal_delay_ms(), which handles both IRQ-enabled and IRQ-disabled contexts correctly.Testing
Built PYBD_SF3 with
CFLAGS_EXTRA=-DMICROPY_HW_TINYUSB_STACK=1(previously failed to link, now builds cleanly). Also built all 79 defined stm32 boards with TinyUSB forced on to confirm no regressions.Trade-offs and Alternatives
Could implement
tusb_time_millis_api()instead, but that leaves the busy-wait in place.tusb_time_delay_ms_api()is the right override since it's the actual call site.Generative AI
I used generative AI tools when creating this PR, but a human has checked the code and is responsible for the description above.