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The port could only run with a periodic ARM SysTick tick. Add an alarm/ oneshot lower-half backed by an RP2350 system timer block so the scheduler can run tickless, waking the CPU only when a timer actually expires. rp23xx_oneshot.c implements the ONESHOT_COUNT lower-half (mirroring the RISC-V mtimer driver). A timer block is a free-running 64-bit microsecond counter (clocked by the TICKS block, independent of the SysTick), which serves directly as the monotonic time base returned by current(), so timekeeping is exact to 1 us. The one adaptation versus a full 64-bit compare timer is that the RP2350 ALARM registers match only the low 32 bits of the counter: max_delay() is therefore capped below 2^32 counts (~71.5 minutes) so the scheduler never asks for a longer interval, and any deadline that is already due -- or that the counter reaches while the alarm is being armed -- is raised immediately through the INTF force register instead of waiting a full 32-bit wrap for the compare to match again. Enabled with CONFIG_RP23XX_SYSTIMER_TICKLESS (mutually exclusive with RP23XX_SYSTIMER_SYSTICK), which selects ONESHOT, ONESHOT_COUNT and ALARM_ARCH; up_timer_initialize() then hands the oneshot to up_alarm_set_lowerhalf(). ARCH_CHIP_RP23XX now selects ARCH_HAVE_TICKLESS. The block is selectable with CONFIG_RP23XX_SYSTIMER_TICKLESS_TIMER0 (default) or _TIMER1; the chosen block is claimed exclusively by the scheduler and is excluded from the /dev/timer driver (CONFIG_RP23XX_TIMER) in Kconfig, so the tickless clock and a /dev/timer device can coexist on different blocks. Tested on Pimoroni Pico Plus 2 (RP2350B) hardware with CONFIG_SCHED_TICKLESS and CONFIG_SCHED_TICKLESS_ALARM: the image boots to nsh and keeps accurate time -- "uptime" advances at real-time rate (17 s over a measured 17.4 s) and "sleep 4" blocks for 4.25 s of wall time -- confirming the oneshot both drives the scheduler and provides a correct 1 MHz monotonic clock. Assisted-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com> Signed-off-by: Marco Casaroli <marco.casaroli@gmail.com> |
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