This issue is meant to track nontrivial users of xtimer or periph_rt*, corner cases that could conflict with a migration to ztimer, or need to be resolved fur such a migration to eventually happen.

Modules depending on 64-bit xtimer Implementation #13667

See #13667 for a tracking issue.

There are two options of addressing this:

• remove the need for 64bit long-running timers (e.g: using ZTIMER_MSEC or ZTIMER_SEC)
• add ztimer64 which will provide the required missing API sys/ztimer64: initial PR #16928

Modules depending on xtimer_ticks_to_usec API

There are two options to address this:

• migrate use cases to not rely on ticks
• implement xtimer_ticks on top of ZTIMER_MSEC_BASE add functions for conversion between ticks and usec like those in xtimer base on ZTIMER_MSEC_BASE_FREQ

API Users:

• drivers/at30tse75x: used to spin can be covnerted to ztimer_spin driver/at30tse75x: port to ztimer_usec #17137
• drivers/at8520e: timeout is set in seconds (max 256) -> can be converted to ZTIMER_SEC or ZTIMER_MSEC drivers/ata8520e: migrate to ztimer #17105
• drivers/dose: use to make sure that sleep time is above XTIMER_BACKOFF, not needed with ztimer.
• drivers/nrf24l01p: used to spin, can be converted to ZTIMER_USEC
• drivers/xbee: wait 1 second with us precision -> 32 bit is enough (one function rewrite) drivers/xbee: migrate to ztimer_msec #17114
• drivers/nvram_spi: used to spin, can be converted to ztimer_spin
• drivers/rn2xx3: timeout is set in seconds (max 256) -> can be converted to ZTIMER_SEC or ZTIMER_MSEC drivers/ata8520e: migrate to ztimer #17105
• drivers/si11rr: a usec timeout that can be updated to not use the ticks api
• paho-mqtt: read timeouts in ms -> use ZTIMER_MSEC : pkg/paho-mqtt: migrate to ztimer #17143
• sys/net/gnrc/netif: periodic wake up in us, can use ZTIMER_USEC gnrc/netif: convert to ztimer #17354
• sys/ps: runtime is measured in ticks -> use ZTIMER_USEC: schedstatistics: Convert to ztimer #17216
• sys/stdio_rtt: there is some polling functionality, probably can be adapted to use usec or even msec, since polling time is 50000 ticks stdio_rtt: Convert to ztimer #17122
• sys/stdio_semihosting: pollrate is in ms, can be switched to ZTIMER_MSEC.

Ztimer conflicts

• ztimer_msec conflicts with direct usage of RTT #17060
• sys/net/gnrc/link_layer/lwmac: uses rtt, could use ZTIMER_MSEC - gnrc_lwmac: use ximer for recording radio duty over RTT #8953
• sys/net/gnrc/link_layer/gomach: uses rttxtimer, could use ZTIMER_MSEC
• simple deep sleep use cases where rtc or rtt are used to wake up the CPU
• active clocks preventing sleep: event/timeout: fixed dependency on ZTIMER_USEC preventing low-power operation #16891

Ztimer other

• ztimer->adjust_sleep and ztimer->adjust_set automatic configuration
• RTT_MIN_OFFSET is not 2 for all CPU's, shuuld be addapted for all
• ztimer multiple backends pottential footgun sys/ztimer: Potential footgun when mixing timestamps of ztimer clocks #16698
• CPU/BOARDs timer width are hardcoded and do not always represent the actual timer backend size TIMER_0_MAX_VALUE