On 2/5/21 12:04 AM, Mathieu Poirier wrote:
On Thu, Jan 28, 2021 at 09:16:34AM +0000, Suzuki K Poulose wrote:
On 1/27/21 8:55 AM, Anshuman Khandual wrote:
Add support for dedicated sinks that are bound to individual CPUs. (e.g, TRBE). To allow quicker access to the sink for a given CPU bound source, keep a percpu array of the sink devices. Also, add support for building a path to the CPU local sink from the ETM.
This adds a new percpu sink type CORESIGHT_DEV_SUBTYPE_SINK_PERCPU_SYSMEM. This new sink type is exclusively available and can only work with percpu source type device CORESIGHT_DEV_SUBTYPE_SOURCE_PERCPU_PROC.
This defines a percpu structure that accommodates a single coresight_device which can be used to store an initialized instance from a sink driver. As these sinks are exclusively linked and dependent on corresponding percpu sources devices, they should also be the default sink device during a perf session.
Outwards device connections are scanned while establishing paths between a source and a sink device. But such connections are not present for certain percpu source and sink devices which are exclusively linked and dependent. Build the path directly and skip connection scanning for such devices.
Cc: Mathieu Poirier mathieu.poirier@linaro.org Cc: Mike Leach mike.leach@linaro.org Cc: Suzuki K Poulose suzuki.poulose@arm.com Signed-off-by: Anshuman Khandual anshuman.khandual@arm.com
Changes in V3:
Updated coresight_find_default_sink()
drivers/hwtracing/coresight/coresight-core.c | 16 ++++++++++++++-- include/linux/coresight.h | 12 ++++++++++++ 2 files changed, 26 insertions(+), 2 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c index 0062c89..4795e28 100644 --- a/drivers/hwtracing/coresight/coresight-core.c +++ b/drivers/hwtracing/coresight/coresight-core.c @@ -23,6 +23,7 @@ #include "coresight-priv.h" static DEFINE_MUTEX(coresight_mutex); +DEFINE_PER_CPU(struct coresight_device *, csdev_sink); /**
- struct coresight_node - elements of a path, from source to sink
@@ -784,6 +785,13 @@ static int _coresight_build_path(struct coresight_device *csdev, if (csdev == sink) goto out;
- if (coresight_is_percpu_source(csdev) && coresight_is_percpu_sink(sink) &&
sink == per_cpu(csdev_sink, source_ops(csdev)->cpu_id(csdev))) {_coresight_build_path(sink, sink, path);The return value for _coresight_build_path() needs to be checked. Otherwise a failure to allocate a node for the sink will go unoticed and make for a very hard problem to debug.
How about this instead ?
diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c index 4795e28..e93e669 100644 --- a/drivers/hwtracing/coresight/coresight-core.c +++ b/drivers/hwtracing/coresight/coresight-core.c @@ -787,9 +787,10 @@ static int _coresight_build_path(struct coresight_device *csdev,
if (coresight_is_percpu_source(csdev) && coresight_is_percpu_sink(sink) && sink == per_cpu(csdev_sink, source_ops(csdev)->cpu_id(csdev))) { - _coresight_build_path(sink, sink, path); - found = true; - goto out; + if (_coresight_build_path(sink, sink, path) == 0) { + found = true; + goto out; + } }
/* Not a sink - recursively explore each port found on this element */
found = true;goto out;- }
- /* Not a sink - recursively explore each port found on this element */ for (i = 0; i < csdev->pdata->nr_outport; i++) { struct coresight_device *child_dev;
@@ -999,8 +1007,12 @@ coresight_find_default_sink(struct coresight_device *csdev) int depth = 0; /* look for a default sink if we have not found for this device */
- if (!csdev->def_sink)
csdev->def_sink = coresight_find_sink(csdev, &depth);
- if (!csdev->def_sink) {
if (coresight_is_percpu_source(csdev))csdev->def_sink = per_cpu(csdev_sink, source_ops(csdev)->cpu_id(csdev));if (!csdev->def_sink)csdev->def_sink = coresight_find_sink(csdev, &depth);- } return csdev->def_sink; }
diff --git a/include/linux/coresight.h b/include/linux/coresight.h index 976ec26..bc3a5ca 100644 --- a/include/linux/coresight.h +++ b/include/linux/coresight.h @@ -50,6 +50,7 @@ enum coresight_dev_subtype_sink { CORESIGHT_DEV_SUBTYPE_SINK_PORT, CORESIGHT_DEV_SUBTYPE_SINK_BUFFER, CORESIGHT_DEV_SUBTYPE_SINK_SYSMEM,
- CORESIGHT_DEV_SUBTYPE_SINK_PERCPU_SYSMEM,
Do we absolutely need to add a new sink type? It is only used in _coresight_build_path() and that code could be:
if (coresight_is_percpu_source(csdev)) { sink == per_cpu(csdev_sink, source_ops(csdev)->cpu_id(csdev));
Do you mean if (sink == per_cpu(...)) above ?
if (sink && sink == csdev) {
How could the sink fetched from the source csdev be the same ?
I would still suggest keeping CORESIGHT_DEV_SUBTYPE_SINK_PERCPU_SYSMEM for logical separation between source and sink, which also improves clarity and readability.