On 13/01/2022 09:10, James Clark wrote:
When enabled, all taken branch addresses are output, even if the branch was because of a direct branch instruction. This enables reconstruction of the program flow without having access to the memory image of the code being executed.
Use bit 8 for the config option which would be the correct bit for programming ETMv3. Although branch broadcast can't be enabled on ETMv3 because it's not in the define ETM3X_SUPPORTED_OPTIONS, using the correct bit might help prevent future collisions or allow it to be enabled if needed.
Signed-off-by: James Clark james.clark@arm.com
drivers/hwtracing/coresight/coresight-etm-perf.c | 2 ++ drivers/hwtracing/coresight/coresight-etm4x-core.c | 10 ++++++++++ include/linux/coresight-pmu.h | 2 ++ 3 files changed, 14 insertions(+)
diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c index c039b6ae206f..43bbd5dc3d3b 100644 --- a/drivers/hwtracing/coresight/coresight-etm-perf.c +++ b/drivers/hwtracing/coresight/coresight-etm-perf.c @@ -52,6 +52,7 @@ static DEFINE_PER_CPU(struct coresight_device *, csdev_src);
- The PMU formats were orignally for ETMv3.5/PTM's ETMCR 'config';
- now take them as general formats and apply on all ETMs.
*/ +PMU_FORMAT_ATTR(branch_broadcast, "config:"__stringify(ETM_OPT_BRANCH_BROADCAST)); PMU_FORMAT_ATTR(cycacc, "config:" __stringify(ETM_OPT_CYCACC)); /* contextid1 enables tracing CONTEXTIDR_EL1 for ETMv4 */ PMU_FORMAT_ATTR(contextid1, "config:" __stringify(ETM_OPT_CTXTID)); @@ -97,6 +98,7 @@ static struct attribute *etm_config_formats_attr[] = { &format_attr_sinkid.attr, &format_attr_preset.attr, &format_attr_configid.attr,
- &format_attr_branch_broadcast.attr,
Does it make sense to hide the option if the bb is not supported ? I guess it will be tricky as we don't track the common feature set. So, that said...
NULL, }; diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c index bf18128cf5de..04669ecc0efa 100644 --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c @@ -692,6 +692,16 @@ static int etm4_parse_event_config(struct coresight_device *csdev, ret = cscfg_csdev_enable_active_config(csdev, cfg_hash, preset); }
- /* branch broadcast - enable if selected and supported */
- if (attr->config & BIT(ETM_OPT_BRANCH_BROADCAST)) {
if (!drvdata->trcbb) {ret = -EINVAL;
Should we fail here ? We could simply ignore this and generate the trace normally. This would work on a big.LITTLE system with one set missing the branch broadcast, while the others support.
Mike,
Does this affect the trace decoding ? As such the OpenCSD should be able to decode the packets as they appear in the stream. Correct ?
Suzuki
goto out;} else {config->cfg |= BIT(ETM4_CFG_BIT_BB);}- }
- out: return ret; }
diff --git a/include/linux/coresight-pmu.h b/include/linux/coresight-pmu.h index 4ac5c081af93..6c2fd6cc5a98 100644 --- a/include/linux/coresight-pmu.h +++ b/include/linux/coresight-pmu.h @@ -18,6 +18,7 @@
- ETMv3.5/PTM doesn't define ETMCR config bits with prefix "ETM3_" and
- directly use below macros as config bits.
*/ +#define ETM_OPT_BRANCH_BROADCAST 8 #define ETM_OPT_CYCACC 12 #define ETM_OPT_CTXTID 14 #define ETM_OPT_CTXTID2 15 @@ -25,6 +26,7 @@ #define ETM_OPT_RETSTK 29 /* ETMv4 CONFIGR programming bits for the ETM OPTs */ +#define ETM4_CFG_BIT_BB 3 #define ETM4_CFG_BIT_CYCACC 4 #define ETM4_CFG_BIT_CTXTID 6 #define ETM4_CFG_BIT_VMID 7