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| author | Ravi Bangoria <ravi.bangoria@amd.com> | 2025-01-15 05:44:37 +0000 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2025-02-03 11:46:06 +0100 |
| commit | fa5d0a824e3bbd1f793d962f9e012ab0a8ee11c5 (patch) | |
| tree | 75b58a833875105b1dfb285b814ff676320338e2 /scripts/lib/kdoc/kdoc_parser.py | |
| parent | 1afbdd970f50f2e0431fae26b25d4e54e561fa7f (diff) | |
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
Diffstat (limited to 'scripts/lib/kdoc/kdoc_parser.py')
0 files changed, 0 insertions, 0 deletions