Messages in this thread | | | Date | Fri, 18 Aug 2023 14:04:20 +0100 | Subject | Re: [PATCH V4 2/3] coresight: etm: Make cycle count threshold user configurable | From | Suzuki K Poulose <> |
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On 18/08/2023 14:01, Mike Leach wrote: > On Fri, 18 Aug 2023 at 12:25, Suzuki K Poulose <suzuki.poulose@arm.com> wrote: >> >> On 18/08/2023 12:20, 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. >>> >>> 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. 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'. >>> >>> Cc: Suzuki K Poulose <suzuki.poulose@arm.com> >>> Cc: Mike Leach <mike.leach@linaro.org> >>> Cc: James Clark <james.clark@arm.com> >>> Cc: Leo Yan <leo.yan@linaro.org> >>> Cc: coresight@lists.linaro.org >>> Cc: linux-arm-kernel@lists.infradead.org >>> Cc: linux-doc@vger.kernel.org >>> Cc: linux-kernel@vger.kernel.org >>> Reviewed-by: Mike Leach <mike.leach@linaro.org> >>> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> >>> --- >>> drivers/hwtracing/coresight/coresight-etm-perf.c | 2 ++ >>> drivers/hwtracing/coresight/coresight-etm4x-core.c | 12 ++++++++++-- >>> 2 files changed, 12 insertions(+), 2 deletions(-) >>> >>> diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c >>> index 5ca6278baff4..09f75dffae60 100644 >>> --- a/drivers/hwtracing/coresight/coresight-etm-perf.c >>> +++ b/drivers/hwtracing/coresight/coresight-etm-perf.c >>> @@ -68,6 +68,7 @@ PMU_FORMAT_ATTR(preset, "config:0-3"); >>> PMU_FORMAT_ATTR(sinkid, "config2:0-31"); >>> /* config ID - set if a system configuration is selected */ >>> PMU_FORMAT_ATTR(configid, "config2:32-63"); >>> +PMU_FORMAT_ATTR(cc_threshold, "config3:0-11"); >>> >>> >>> /* >>> @@ -101,6 +102,7 @@ static struct attribute *etm_config_formats_attr[] = { >>> &format_attr_preset.attr, >>> &format_attr_configid.attr, >>> &format_attr_branch_broadcast.attr, >>> + &format_attr_cc_threshold.attr, >>> NULL, >>> }; >>> >>> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c >>> index 591fab73ee79..3193dafa7618 100644 >>> --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c >>> +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c >>> @@ -635,7 +635,7 @@ static int etm4_parse_event_config(struct coresight_device *csdev, >>> struct etmv4_config *config = &drvdata->config; >>> struct perf_event_attr *attr = &event->attr; >>> unsigned long cfg_hash; >>> - int preset; >>> + int preset, cc_threshold; >>> >>> /* Clear configuration from previous run */ >>> memset(config, 0, sizeof(struct etmv4_config)); >>> @@ -658,7 +658,15 @@ static int etm4_parse_event_config(struct coresight_device *csdev, >>> if (attr->config & BIT(ETM_OPT_CYCACC)) { >>> config->cfg |= TRCCONFIGR_CCI; >>> /* TRM: Must program this for cycacc to work */ >>> - config->ccctlr = ETM_CYC_THRESHOLD_DEFAULT; >>> + cc_threshold = attr->config3 & ETM_CYC_THRESHOLD_MASK; >>> + if (cc_threshold) { >>> + if (cc_threshold < drvdata->ccitmin) >>> + config->ccctlr = drvdata->ccitmin; >>> + else >>> + config->ccctlr = cc_threshold; >>> + } else { >>> + config->ccctlr = ETM_CYC_THRESHOLD_DEFAULT; >> >> Ideally this must be the ccitmin ? Theoretically, default value could be >> bigger than the minimum value supported by the implementation (i.e., >> ccitmin) >> >> Suzuki >> > > In order not to change existing behaviour unexpectedly this could be > re-ordered... > > cc_threshold = attr->config3 & ETM_CYC_THRESHOLD_MASK; > if (!cc_threshold) > cc_threshold = ETM_CYC_THRESHOLD_DEFAULT; > if (cc_threshold < drvdata->ccitmin) > cc_threshold = drvdata->ccitmin > config->ccctlr = cc_threshold;
That sounds better, Thanks Mike
Suzuki
> > Mike >>> + } >>> } >>> if (attr->config & BIT(ETM_OPT_TS)) { >>> /* >> > >
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