• Lorenzo Pieralisi's avatar
    drivers/perf: arm_pmu: implement CPU_PM notifier · da4e4f18
    Lorenzo Pieralisi authored
    When a CPU is suspended (either through suspend-to-RAM or CPUidle),
    its PMU registers content can be lost, which means that counters
    registers values that were initialized on power down entry have to be
    reprogrammed on power-up to make sure the counters set-up is preserved
    (ie on power-up registers take the reset values on Cold or Warm reset,
    which can be architecturally UNKNOWN).
    
    To guarantee seamless profiling conditions across a core power down
    this patch adds a CPU PM notifier to ARM pmus, that upon CPU PM
    entry/exit from low-power states saves/restores the pmu registers
    set-up (by using the ARM perf API), so that the power-down/up cycle does
    not affect the perf behaviour (apart from a black-out period between
    power-up/down CPU PM notifications that is unavoidable).
    
    Cc: Will Deacon <will.deacon@arm.com>
    Cc: Sudeep Holla <sudeep.holla@arm.com>
    Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
    Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
    Cc: Mark Rutland <mark.rutland@arm.com>
    Acked-by: default avatarAshwin Chaugule <ashwin.chaugule@linaro.org>
    Acked-by: default avatarKevin Hilman <khilman@baylibre.com>
    Signed-off-by: default avatarLorenzo Pieralisi <lorenzo.pieralisi@arm.com>
    Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
    da4e4f18
arm_pmu.c 24.5 KB