Re: [PATCH V5 - RESEND 2/3] coresight: etm: Make cycle count threshold user configurable
From: Suzuki K Poulose <suzuki.poulose@arm.com>
Date: 2023-09-20 09:22:42
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linux-arm-kernel, lkml
On 15/09/2023 10:36, Anshuman Khandual wrote:
Cycle counting is enabled, when requested and supported but with a default threshold value ETM_CYC_THRESHOLD_DEFAULT i.e 0x100 getting into TRCCCCTLR, representing the minimum interval between cycle count trace packets.
minor nit: When Cycle counting is enabled, we use a default threshold value (0x100) for the instruction trace cycle counting.
This makes cycle threshold user configurable, from the user space via perf event attributes. Although it falls back using ETM_CYC_THRESHOLD_DEFAULT, in case no explicit request.
Minor nit: This patch makes the cycle threshold user configurable via perf event attributes( 'cc_threshold' => event->attr.config3[11:0] ), falling back to the the current default if unspecified.
As expected it creates a sysfs file as well.
/sys/bus/event_source/devices/cs_etm/format/cc_threshold New 'cc_threshold' uses 'event->attr.config3' as no more space is available in 'event->attr.config1' or 'event->attr.config2'.
Trim the above part. Rest looks fine to me. Suzuki