Messages in this thread | | | From | Anshuman Khandual <> | Subject | Re: [PATCH V2 08/11] coresight: core: Add support for dedicated percpu sinks | Date | Fri, 15 Jan 2021 08:06:31 +0530 |
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On 1/13/21 3:13 PM, Suzuki K Poulose wrote: > On 1/13/21 4:18 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> >> --- >> drivers/hwtracing/coresight/coresight-core.c | 14 ++++++++++++++ >> include/linux/coresight.h | 12 ++++++++++++ >> 2 files changed, 26 insertions(+) >> >> diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c >> index 0062c89..b300606 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); >> + 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; >> @@ -998,6 +1006,12 @@ coresight_find_default_sink(struct coresight_device *csdev) >> { >> int depth = 0; >> + if (coresight_is_percpu_source(csdev)) { > > On a system without per_cpu sink, this would reset the default sink for the source device > every single time and fallback to searching every single time.
Right.
> So I think it would be better if did check if the def_sink was not set. > We could fold this into the case below may be. i.e, > > > 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); > } > > Otherwise looks good to me.
struct coresight_device * 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) { 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; }
Would this be better instead ? coresight_find_sink() is invoked both when the source is not percpu (traditional coresight sources) and also as a fallback in case a percpu sink is not found for the percpu source device.
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