nuttx/arch/arm
Jacob Dahl 304cbb1372 arch/arm/stm32h7: poll MDIO completion in microseconds, not 5 ms steps
stm32_c22_read() and stm32_c22_write() waited for the MACMDIOAR busy bit
with up_mdelay(5) between checks. A Clause 22 frame takes about 30 us,
so the first check always sees the bus busy and every PHY register
access costs a 5 ms busy-wait, roughly 150 times the transfer.

stm32_phyinit() waits for link-up with PHY_RETRY_TIMEOUT (6552) MSR
reads. With no cable attached that is 33 s of CPU spent in
up_mdelay() inside ifup, with the network lock held: on an STM32H753
the netinit thread pinned the core at 44% for the first 65 s after
boot and every socket operation on other threads blocked until it gave
up. Before the MDIO bus refactor, stm32_phyread() polled the busy bit
in a tight loop.

Poll every 10 us instead, with the timeout expressed in microseconds so
the total bound stays at 10 ms, and report the timeout from the result
rather than the loop counter so a transfer that completes on the last
iteration is not logged as timed out.

Signed-off-by: Jacob Dahl <dahl.jakejacob@gmail.com>
2026-09-07 09:57:52 -03:00
..
include arch/arm/stm32f4: add STM32F412CG chip selection 2026-09-01 17:40:30 +08:00
src arch/arm/stm32h7: poll MDIO completion in microseconds, not 5 ms steps 2026-09-07 09:57:52 -03:00
CMakeLists.txt arch/arm: migrate to SPDX identifier 2024-12-06 09:25:23 +08:00
Kconfig arch/arm/src: realize atomic for cxd56, rp2040 and lc823450 2026-08-27 11:13:29 +08:00