The CONFIG_CLOCK_CONTROL and CONFIG_NRF_RTC_TIMER were
unconditionally selected when enabling any nRF SoC. But since
timers can be disabled in the kernel, depend instead on
CONFIG_SYS_CLOCK_EXISTS, which is only defined when kernel
timer support is included.
Note that ideally we would enable CONFIG_NRF_RTC_TIMER only, and
that would select CONFIG_CLOCK_CONTROL (on which the RTC timer
depends) but there is a circular Kconfig dependency that prevents
us from doing so.
Signed-off-by: Carles Cufi <carles.cufi@nordicsemi.no>
The default system clock on all Nordic devices is based on a 32 KiHz
(2^15 Hz) timer. Scheduling ticks requires that deadlines be specified
with a timer counter that aligns to a system clock. With the Zephyr
default 100 clocks-per-sec configuration this results in 100 ticks every
32700 ticks of the cycle timer. This reveals two problems:
* The uptime clock misrepresents elapsed time because it runs 0.208%
(68/32768) faster than the best available clock;
* Calculation of timer counter compare values often requires an integer
division and multiply operation to produce a value that's a multiple
of clock-ticks-per-second.
Integer division on the Cortex-M1 nRF51 is done in software with a
(value-dependent) algorithm with a non-constant runtime that can be
significant. This can produce missed Bluetooth deadlines as discussed
in upstream #14577 and others.
By changing the default divisor to one that evenly divides the 2^15
clock rate the time interrupts are disabled to manage timers is
significantly reduced, as is the error between uptime and real time. Do
this at the top level, moving SYS_CLOCK_HW_CYCLES_PER_SEC there as well
since the two parameters are related.
Note that the central_hr configuration described in upstream #13610 does
not distinguish latency due to timer management from other
irq_block/spinlock regions, and the maximum observed latency will still
exceed the nominal 10 us allowed maximum. However this does occur
much less frequently than changing the timer deadline which can happen
multiple times per tick.
Signed-off-by: Peter A. Bigot <pab@pabigot.com>
This reverts commit d4b4b99272 as it
introduced unwanted side effect: It moved the k_busy_wait() to other
clock that the one driving system timer and k_cycle_get_32(). As result,
delays created using these interfaces not matched each other.
Signed-off-by: Piotr Zięcik <piotr.ziecik@nordicsemi.no>
Implementation taken from Nordic nrfx version 1.3.1 soc/nrfx_coredep.h,
modified to remove material from other series and to conform to Zephyr
coding standards.
Note that unlike standard k_busy_wait this is susceptible to
longer-than-intended delays due to the impact of interrupt handling.
Fixes#11626
Signed-off-by: Peter A. Bigot <pab@pabigot.com>
This can help find unused symbols. Those end up without a type if
'default' is used instead of 'def_bool', which generates a warning.
Search for "Kconfig.defconfig" in
https://docs.zephyrproject.org/latest/application/kconfig-tips.html for
a longer explanation.
Keep the 'def_bool' for the following symbols, which seem to be
deliberately defined only in Kconfig.defconfig files:
- ALTERA_AVALON_I2C
- ALTERA_AVALON_MSGDMA
- ALTERA_AVALON_PIO
- ALTERA_AVALON_QSPI
- ALTERA_AVALON_SYSID
- CLOCK_CONTROL_IMX_CCM
- CPU_EM4_DMIPS
- CPU_EM4_FPUDA
- CPU_EM4_FPUS
- FP_FPU_DA
- I2C_GECKO
Signed-off-by: Ulf Magnusson <Ulf.Magnusson@nordicsemi.no>
Move the SoC outside of the architecture tree and put them at the same
level as boards and architectures allowing both SoCs and boards to be
maintained outside the tree.
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
Carles Cufi