Messages in this thread | | | Subject | Re: [PATCH V2 08/11] coresight: core: Add support for dedicated percpu sinks | From | Suzuki K Poulose <> | Date | Fri, 15 Jan 2021 12:31:14 +0000 |
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On 1/15/21 2:36 AM, Anshuman Khandual wrote: > > > 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. Yes, this is exactly what I proposed above.
Cheers Suzuki
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