Add clocks property to CPUs in nRF54L series which can be used to get CPU clock frequency #83527
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Add clocks property to CPUs. nRF54Lx series is using hfpll as clock source for CPU (and fast peripherals). CPU clock frequency can be derived from frequency of the source clock so clock-frequency property is removed from cpu as it is redundant. nrfx/MDK expects that NRF_CONFIG_CPU_FREQ_MHZ define is set to correct CPU frequency. Modified nrfx CMakeLists.txt to use clock frequency of hfpll instead of CPU clock-frequency property. Signed-off-by: Krzysztof Chruściński <krzysztof.chruscinski@nordicsemi.no>
nrf54l20pdk must use 64 MHz for now. So far it was done by using SOC_NRF54LX_SKIP_CLOCK_CONFIG Kconfig option which was skipping oscillator configuration so that it was running the default frequency (which is 64 MHz). This approach was a bit cryptic because DT was indicating that CPU was running 128 MHz when actual frequency was different (and it was relying on assumption that default frequency is 64 MHz). After adding hfpll as clock source for CPU Kconfig option can be replaced with DT setting where actual frequency is correctly indicated. Since hfpll is a clock source for fast peripherals (e.g. TIMER00) it is possible to have single source of information regarding frequency. Signed-off-by: Krzysztof Chruściński <krzysztof.chruscinski@nordicsemi.no>
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Jan 6, 2025
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| dt_prop(clock-frequency PATH "/clocks/hfpll" PROPERTY "clock-frequency") | ||
| math(EXPR clock_frequency_mhz "${clock_frequency} / 1000000") |
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The clock-frequency on line 187 has a dash in it, ${clock_frequency} on line 188 does not, is this expected?
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nRF54L CPUs and fast peripherals can run at 64 MHz or 128 MHz. So far DT was indicating that CPU is running at 128 MHz and changing that to 64 MHz did not result in changing actual CPU frequency. On the other hand to use 64 MHz a cryptic Kconfig had to be set (
CONFIG_SOC_NRF54LX_SKIP_CLOCK_CONFIG=y).Added
clocks = <&hfpll>property to CPU cores in nRF54L and reworked cmake file so that changinghfpllfrequency in DT results in changing CPU frequency.#82901 is adding same property to TIMERs so that there will be a single source of truth regarding frequency of peripherals clocked by the same source.