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@xxxxxxx>
---
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
