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    SubjectRe: [PATCH v4 17/19] coresight: core: Add support for dedicated percpu sinks
    On Thu, Feb 25, 2021 at 07:35:41PM +0000, Suzuki K Poulose wrote:
    > From: Anshuman Khandual <anshuman.khandual@arm.com>
    >
    > 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_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>
    > Tested-by: Suzuki K Poulose <suzuki.poulose@arm.com>
    > Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
    > Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
    > [Moved the set/get percpu sink APIs from TRBE patch to here]
    > Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
    > ---
    > Changes:
    > - Export methods to set/get percpu sinks for fixing module
    > build for TRBE
    > - Addressed coding style comments (Suzuki)
    > - Check status of _coresight_build_path() (Mathieu)
    > ---
    > drivers/hwtracing/coresight/coresight-core.c | 29 ++++++++++++++++++--
    > drivers/hwtracing/coresight/coresight-priv.h | 3 ++
    > include/linux/coresight.h | 12 ++++++++
    > 3 files changed, 42 insertions(+), 2 deletions(-)

    Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>

    >
    > diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
    > index 0062c8935653..55c645616bf6 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
    > @@ -70,6 +71,18 @@ void coresight_remove_cti_ops(void)
    > }
    > EXPORT_SYMBOL_GPL(coresight_remove_cti_ops);
    >
    > +void coresight_set_percpu_sink(int cpu, struct coresight_device *csdev)
    > +{
    > + per_cpu(csdev_sink, cpu) = csdev;
    > +}
    > +EXPORT_SYMBOL_GPL(coresight_set_percpu_sink);
    > +
    > +struct coresight_device *coresight_get_percpu_sink(int cpu)
    > +{
    > + return per_cpu(csdev_sink, cpu);
    > +}
    > +EXPORT_SYMBOL_GPL(coresight_get_percpu_sink);
    > +
    > static int coresight_id_match(struct device *dev, void *data)
    > {
    > int trace_id, i_trace_id;
    > @@ -784,6 +797,14 @@ 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))) {
    > + if (_coresight_build_path(sink, sink, path) == 0) {
    > + 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 +1020,12 @@ 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/drivers/hwtracing/coresight/coresight-priv.h b/drivers/hwtracing/coresight/coresight-priv.h
    > index f5f654ea2994..ff1dd2092ac5 100644
    > --- a/drivers/hwtracing/coresight/coresight-priv.h
    > +++ b/drivers/hwtracing/coresight/coresight-priv.h
    > @@ -232,4 +232,7 @@ coresight_find_csdev_by_fwnode(struct fwnode_handle *r_fwnode);
    > void coresight_set_assoc_ectdev_mutex(struct coresight_device *csdev,
    > struct coresight_device *ect_csdev);
    >
    > +void coresight_set_percpu_sink(int cpu, struct coresight_device *csdev);
    > +struct coresight_device *coresight_get_percpu_sink(int cpu);
    > +
    > #endif
    > diff --git a/include/linux/coresight.h b/include/linux/coresight.h
    > index 976ec2697610..8a3a3c199087 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,
    > };
    >
    > enum coresight_dev_subtype_link {
    > @@ -428,6 +429,17 @@ static inline void csdev_access_write64(struct csdev_access *csa, u64 val, u32 o
    > csa->write(val, offset, false, true);
    > }
    >
    > +static inline bool coresight_is_percpu_source(struct coresight_device *csdev)
    > +{
    > + return csdev && (csdev->type == CORESIGHT_DEV_TYPE_SOURCE) &&
    > + (csdev->subtype.source_subtype == CORESIGHT_DEV_SUBTYPE_SOURCE_PROC);
    > +}
    > +
    > +static inline bool coresight_is_percpu_sink(struct coresight_device *csdev)
    > +{
    > + return csdev && (csdev->type == CORESIGHT_DEV_TYPE_SINK) &&
    > + (csdev->subtype.sink_subtype == CORESIGHT_DEV_SUBTYPE_SINK_PERCPU_SYSMEM);
    > +}
    > #else /* !CONFIG_64BIT */
    >
    > static inline u64 csdev_access_relaxed_read64(struct csdev_access *csa,
    > --
    > 2.24.1
    >

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