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SubjectRe: [PATCH v2 3/7] coresight: Use event attributes for sink selection
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On 01/22/2019 06:11 PM, Mathieu Poirier wrote:
> This patch uses the information conveyed by perf_event::attr::config2
> to select a sink to use for the session. That way a sink can easily be
> selected to be used by more than one source, something that isn't currently
> possible with the sysfs implementation.
>
> Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
> ---
> .../hwtracing/coresight/coresight-etm-perf.c | 24 ++++++------
> drivers/hwtracing/coresight/coresight-priv.h | 1 +
> drivers/hwtracing/coresight/coresight.c | 39 +++++++++++++++++++
> 3 files changed, 52 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
> index c68a0036532c..ea031eb673b3 100644
> --- a/drivers/hwtracing/coresight/coresight-etm-perf.c
> +++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
> @@ -31,11 +31,14 @@ static DEFINE_PER_CPU(struct coresight_device *, csdev_src);
> PMU_FORMAT_ATTR(cycacc, "config:" __stringify(ETM_OPT_CYCACC));
> PMU_FORMAT_ATTR(timestamp, "config:" __stringify(ETM_OPT_TS));
> PMU_FORMAT_ATTR(retstack, "config:" __stringify(ETM_OPT_RETSTK));
> +/* Sink ID - same for all ETMs */
> +PMU_FORMAT_ATTR(sinkid, "config2:0-31");
>
> static struct attribute *etm_config_formats_attr[] = {
> &format_attr_cycacc.attr,
> &format_attr_timestamp.attr,
> &format_attr_retstack.attr,
> + &format_attr_sinkid.attr,
> NULL,
> };
>
> @@ -191,6 +194,7 @@ static void etm_free_aux(void *data)
> static void *etm_setup_aux(struct perf_event *event, void **pages,
> int nr_pages, bool overwrite)
> {
> + u32 id;
> int cpu = event->cpu;
> cpumask_t *mask;
> struct coresight_device *sink;
> @@ -201,18 +205,14 @@ static void *etm_setup_aux(struct perf_event *event, void **pages,
> return NULL;
> INIT_WORK(&event_data->work, free_event_data);
>
> - /*
> - * In theory nothing prevent tracers in a trace session from being
> - * associated with different sinks, nor having a sink per tracer. But
> - * until we have HW with this kind of topology we need to assume tracers
> - * in a trace session are using the same sink. Therefore go through
> - * the coresight bus and pick the first enabled sink.
> - *
> - * When operated from sysFS users are responsible to enable the sink
> - * while from perf, the perf tools will do it based on the choice made
> - * on the cmd line. As such the "enable_sink" flag in sysFS is reset.
> - */
> - sink = coresight_get_enabled_sink(true);
> + /* First get the selected sink from user space. */
> + if (event->attr.config2) {
> + id = (u32)event->attr.config2;
> + sink = coresight_get_sink_by_id(id);
> + } else {
> + sink = coresight_get_enabled_sink(true);
> + }
> +
> if (!sink || !sink_ops(sink)->alloc_buffer)
> goto err;
>
> diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/hwtracing/coresight/coresight-priv.h
> index 579f34943bf1..b936c6d7e13f 100644
> --- a/drivers/hwtracing/coresight/coresight-priv.h
> +++ b/drivers/hwtracing/coresight/coresight-priv.h
> @@ -147,6 +147,7 @@ void coresight_disable_path(struct list_head *path);
> int coresight_enable_path(struct list_head *path, u32 mode, void *sink_data);
> struct coresight_device *coresight_get_sink(struct list_head *path);
> struct coresight_device *coresight_get_enabled_sink(bool reset);
> +struct coresight_device *coresight_get_sink_by_id(u32 id);
> struct list_head *coresight_build_path(struct coresight_device *csdev,
> struct coresight_device *sink);
> void coresight_release_path(struct list_head *path);
> diff --git a/drivers/hwtracing/coresight/coresight.c b/drivers/hwtracing/coresight/coresight.c
> index d7fa90be6f42..c5f2df186a19 100644
> --- a/drivers/hwtracing/coresight/coresight.c
> +++ b/drivers/hwtracing/coresight/coresight.c
> @@ -11,6 +11,7 @@
> #include <linux/err.h>
> #include <linux/export.h>
> #include <linux/slab.h>
> +#include <linux/stringhash.h>
> #include <linux/mutex.h>
> #include <linux/clk.h>
> #include <linux/coresight.h>
> @@ -541,6 +542,44 @@ struct coresight_device *coresight_get_enabled_sink(bool deactivate)
> return dev ? to_coresight_device(dev) : NULL;
> }
>
> +static int coresight_sink_by_id(struct device *dev, void *data)
> +{
> + struct coresight_device *csdev = to_coresight_device(dev);
> + u32 hash;
> +
> + if (csdev->type == CORESIGHT_DEV_TYPE_SINK ||
> + csdev->type == CORESIGHT_DEV_TYPE_LINKSINK) {
> + /*
> + * See function etm_perf_sink_name_show() to know where this
> + * comes from.
> + */
> + hash = hashlen_hash(hashlen_string(NULL, dev_name(dev)));
> +
> + if (hash == (*(u32 *)data))
> + return 1;
> + }
> +
> + return 0;
> +}
> +
> +/**
> + * coresight_get_sink_by_id - returns the sink that matches the id
> + * @id: Id of the sink to match
> + *
> + * The name of a sink is unique, whether it is found on the AMBA bus or
> + * otherwise. As such the hash of that name can easily be used to identify
> + * a sink.
> + */
> +struct coresight_device *coresight_get_sink_by_id(u32 id)
> +{
> + struct device *dev = NULL;
> +
> + dev = bus_find_device(&coresight_bustype, NULL, &id,
> + coresight_sink_by_id);
> +
> + return dev ? to_coresight_device(dev) : NULL;
> +}
> +

The patch looks good to me. As mentioned in the previous patch, we may
be able to optimize the look up a bit using dev_ext_attribute. Either
way,

Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>

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