To:     will@kernel.org, mark.rutland@arm.com, peterz@infradead.org,
        mingo@redhat.com, acme@kernel.org,
        alexander.shishkin@linux.intel.com, jolsa@kernel.org,
        namhyung@kernel.org, irogers@google.com, linux@armlinux.org.uk
Cc:     linux-arm-kernel@lists.infradead.org,
        linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org
From:   wangxiaolei <xiaolei.wang@windriver.com>
Subject: perf record -e branch-misses ls > /dev/null
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Date:   Wed, 8 Mar 2023 15:56:41 +0800
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hi

When I use the perf tool on nxp-imx6sx, the CPU is armv7 cortex-A9 to 
test, I execute the perf record -e branch-misses ls > /dev/null command, 
but the perf report result is indeed:
perf report
Error:
The perf.data data has no samples!
# To display the perf.data header info, please use 
--header/--header-only options.

root@nxp-imx6:~# perf list hardware

List of pre-defined events (to be used in -e):

    branch-instructions OR branches [Hardware event]
    branch-misses [Hardware event]
    bus-cycles [Hardware event]
    cache-misses [Hardware event]
    cache-references [Hardware event]
    cpu-cycles OR cycles [Hardware event]
    instructions [Hardware event]

And not only this one hardware event, only cycles are working normally 
in the following supported hardware time, other hardware events are not 
interrupted and reported, and the value in the read PMXEVCNTR register 
is always -1, and the PMCR register E, bit[0 ] it will be written to 0 
before reading the PMXEVCNTR register. I don’t know if the value in the 
PMXEVCNTR register is always -1 for this reason. Does anyone have any 
good suggestions for debugging this problem?


thanks

xiaolei