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Message-ID: <e29f83cc-6a00-0e5a-20ca-55d39dc2e3a3@arm.com>
Date: Wed, 20 Sep 2023 10:22:33 +0100
From: Suzuki K Poulose <suzuki.poulose@....com>
To: Anshuman Khandual <anshuman.khandual@....com>,
linux-arm-kernel@...ts.infradead.org
Cc: Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>,
Mike Leach <mike.leach@...aro.org>,
James Clark <james.clark@....com>,
Leo Yan <leo.yan@...aro.org>, Jonathan Corbet <corbet@....net>,
linux-doc@...r.kernel.org, coresight@...ts.linaro.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH V5 - RESEND 2/3] coresight: etm: Make cycle count
threshold user configurable
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
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