perf/amd/ibs: Ceil sample_period to min_period

perf/amd/ibs: Ceil sample_period to min_period

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