perf/imx_ddr: speed up overflow frequency of cycle

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For i.MX8MP, we cannot ensure that cycle counter overflow occurs at least
4 times as often as other events. Due to byte counters will count for any
event configured, it will overflow more often. And if byte counters
overflow that related counters would stop since they share the
COUNTER_CNTL. We can speed up cycle counter overflow frequency by setting
counter parameter (CP) field of cycle counter. In this way, we can avoid
stop counting byte counters when interrupt didn't come and the byte
counters can be fetched or updated from each cycle counter overflow
interrupt.

Because we initialize CP filed to shorten counter0 overflow time, the cycle
counter will start couting from a fixed/base value each time. We need to
remove the base from the result too. Therefore, we could get precise result
from cycle counter.

Signed-off-by: Xu Yang <xu.yang_2@nxp.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://lore.kernel.org/r/20230811015438.1999307-1-xu.yang_2@nxp.com
Signed-off-by: Will Deacon <will@kernel.org>

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Xu Yang 2023-08-11 09:54:37 +08:00 • committed by Will Deacon

parent 83a6d80c2b

commit e89ecd8368

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drivers/perf/fsl_imx8_ddr_perf.c

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