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The sample_period needs to be recalibrated after every sample to match the desired sampling freq for a 'freq mode event'. Since the next sample_period is calculated by generic kernel, PMU specific constraints are not (explicitly) reckoned. The sample_period value is programmed in a MaxCnt field of IBS PMUs, and the MaxCnt field has following constraints: 1) MaxCnt must be multiple of 0x10. Kernel keeps track of residual / over-counted period into period_left, which should take care of this constraint by programming MaxCnt with (sample_period & ~0xF) and adding remaining period into the next sample. 2) MaxCnt must be >= 0x10 for IBS Fetch PMU and >= 0x90 for IBS Op PMU. Currently, IBS PMU driver allows sample_period below min_period, which is an undefined HW behavior. Reset sample_period to min_period whenever it's less than that. Signed-off-by: Ravi Bangoria <ravi.bangoria@amd.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20250115054438.1021-9-ravi.bangoria@amd.com