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Getting zeros on i.MX6 PMU counters using Device Tree Kernel

Question asked by Ben Rathke on Oct 15, 2014
Latest reply on Oct 27, 2014 by alejandrolozano

I'm having the exact problem that was nicely described in an earlier post regarding pre-DT kernels: Getting zeros on i.MX6 PMU counters


My kernel is 3.10.17. I can "fix" this by somewhat blindly pasting the suggested assembly snippet into the cpu_pmu_device_probe function in arch/arm/kernel/perf_event_cpu.c:


u32 val = 0b11;
asm volatile("mcr p15, 0, %0, c1, c1, 1" : : "r" (val));


I'm hoping that there is a more elegant way of doing this. Device tree item perhaps? Has anyone else run into this problem?