On 8/18/23 18:34, Suzuki K Poulose wrote:
> On 18/08/2023 14:01, Mike Leach wrote:
>> On Fri, 18 Aug 2023 at 12:25, Suzuki K Poulose <suzuki.poulose@xxxxxxx> 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@xxxxxxx>
>>>> Cc: Mike Leach <mike.leach@xxxxxxxxxx>
>>>> Cc: James Clark <james.clark@xxxxxxx>
>>>> Cc: Leo Yan <leo.yan@xxxxxxxxxx>
>>>> Cc: coresight@xxxxxxxxxxxxxxxx
>>>> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
>>>> Cc: linux-doc@xxxxxxxxxxxxxxx
>>>> Cc: linux-kernel@xxxxxxxxxxxxxxx
>>>> Reviewed-by: Mike Leach <mike.leach@xxxxxxxxxx>
>>>> Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
>>>> ---
>>>> 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
Sure, will change as suggested.
