Hi James
On 13/01/2022 09:10, James Clark wrote:
Maintain consistency with the other options by failing to open when they aren't supported. For example ETM_OPT_TS, ETM_OPT_CTXTID2 and the newly added ETM_OPT_BRANCH_BROADCAST all return with -EINVAL if they are requested but not supported by hardware.
Looking at this again (with similar comment to the Branch Broadcast), won't it disable using retstack on all CPUs, even when some of them support it ?
i.e., CPU0 - supports retstack, CPU1 - doesn't
A perf run with retstack will fail, as CPU1 doesn't support it (even though we advertise it, unconditionally).
So, if we ignore the failure, this would still allow CPU0 to use the feature and as long as the OpenCSD is able to decode the trace we should ignore the failure ?
I think we may also need to tune the etm4x_enable_hw() to skip updating the TRCCONFIGR with features not supported by the ETM
Suzuki
The consequence of not doing this is that the user may not be aware that they are not enabling the feature as it is silently disabled.
Signed-off-by: James Clark james.clark@arm.com
drivers/hwtracing/coresight/coresight-etm4x-core.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c index 04669ecc0efa..a93c1a5fe045 100644 --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c @@ -674,10 +674,15 @@ static int etm4_parse_event_config(struct coresight_device *csdev, } /* return stack - enable if selected and supported */
- if ((attr->config & BIT(ETM_OPT_RETSTK)) && drvdata->retstack)
/* bit[12], Return stack enable bit */config->cfg |= BIT(12);
- if (attr->config & BIT(ETM_OPT_RETSTK)) {
if (!drvdata->retstack) {ret = -EINVAL;goto out;} else {/* bit[12], Return stack enable bit */config->cfg |= BIT(12);}- } /*
- Set any selected configuration and preset.