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c2eff582a3
This patch adds the barebones of the PMU logic by enabling cycle counting. The overall logic goes as follows: - MMCR0 reg initial value is set to 0x80000000 (MMCR0_FC set) to avoid having to spin the PMU right at system init; - to retrieve the events that are being profiled, pmc_get_event() will check the current MMCR0 and MMCR1 value and return the appropriate PMUEventType. For PMCs 1-4, event 0x2 is the implementation dependent value of PMU_EVENT_INSTRUCTIONS and event 0x1E is the implementation dependent value of PMU_EVENT_CYCLES. These events are supported by IBM Power chips since Power8, at least, and the Linux Perf driver makes use of these events until kernel v5.15. For PMC1, event 0xF0 is the architected PowerISA event for cycles. Event 0xFE is the architected PowerISA event for instructions; - if the counter is frozen, either via the global MMCR0_FC bit or its individual frozen counter bits, PMU_EVENT_INACTIVE is returned; - pmu_update_cycles() will go through each counter and update the values of all PMCs that are counting cycles. This function will be called every time a MMCR0 update is done to keep counters values up to date. Upcoming patches will use this function to allow the counters to be properly updated during read/write of the PMCs and MMCR1 writes. Given that the base CPU frequency is fixed at 1Ghz for both powernv and pseries clock, cycle calculation assumes that 1 nanosecond equals 1 CPU cycle. Cycle value is then calculated by adding the elapsed time, in nanoseconds, of the last cycle update done via pmu_update_cycles(). Reviewed-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com> Message-Id: <20211201151734.654994-3-danielhb413@gmail.com> Signed-off-by: Cédric Le Goater <clg@kaod.org> |
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