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SubjectRe: [PATCH v2 2/7] coresight: perf: Add "sinks" group to PMU directory
On Wed, 30 Jan 2019 at 10:42, Suzuki K Poulose <suzuki.poulose@arm.com> wrote:
>
> Hi Mathieu,
>
>
> On 01/22/2019 06:11 PM, Mathieu Poirier wrote:
> > Add a "sinks" directory entry so that users can see all the sinks
> > available in the system in a single place. Individual sink are added
> > as they are registered with the coresight bus.
>
> A couple of minor comments.
>
> >
> > Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
> > ---
> > .../hwtracing/coresight/coresight-etm-perf.c | 76 +++++++++++++++++++
> > .../hwtracing/coresight/coresight-etm-perf.h | 6 +-
> > drivers/hwtracing/coresight/coresight.c | 18 +++++
> > include/linux/coresight.h | 7 +-
> > 4 files changed, 104 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
> > index f21eb28b6782..c68a0036532c 100644
> > --- a/drivers/hwtracing/coresight/coresight-etm-perf.c
> > +++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
> > @@ -14,6 +14,7 @@
> > #include <linux/perf_event.h>
> > #include <linux/percpu-defs.h>
> > #include <linux/slab.h>
> > +#include <linux/stringhash.h>
> > #include <linux/types.h>
> > #include <linux/workqueue.h>
> >
> > @@ -43,8 +44,18 @@ static const struct attribute_group etm_pmu_format_group = {
> > .attrs = etm_config_formats_attr,
> > };
> >
> > +static struct attribute *etm_config_sinks_attr[] = {
> > + NULL,
> > +};
> > +
> > +static const struct attribute_group etm_pmu_sinks_group = {
> > + .name = "sinks",
> > + .attrs = etm_config_sinks_attr,
> > +};
> > +
> > static const struct attribute_group *etm_pmu_attr_groups[] = {
> > &etm_pmu_format_group,
> > + &etm_pmu_sinks_group,
> > NULL,
> > };
>
> I was thinking if this could be the "events" directory for ETM pmu. We
> don't have any other event codes. Even if we get in the future, we could
> expose them here. But from a quick try it looks like the event names
> cannot start with a number (e.g, 2007000.etr wouldn't parse as an event
> name). So we could leave this as above and switch when we get generic
> naming scheme.
>
> >
> > @@ -479,6 +490,71 @@ int etm_perf_symlink(struct coresight_device *csdev, bool link)
> > return 0;
> > }
> >
> > +static ssize_t etm_perf_sink_name_show(struct device *dev,
> > + struct device_attribute *dattr,
> > + char *buf)
> > +{
> > + /* See function coresight_get_sink_by_id() to know where this is used */
> > + u32 hash = hashlen_hash(hashlen_string(NULL, dattr->attr.name));
> > +
> > + return scnprintf(buf, PAGE_SIZE, "%x\n", hash);
> > +}
>
> You may need "0x%x" to avoid confusions interpreting the data.

Yes

>
> > +
> > +int etm_perf_add_symlink_sink(struct coresight_device *csdev)
> > +{
> > + int ret;
> > + struct device *pmu_dev = etm_pmu.dev;
> > + struct device *pdev = csdev->dev.parent;
> > + struct device_attribute *dattr;
>
> If we make this a struct dev_ext_attribute(), you get a space to
> store the "id" in the "var" field. This can be used for

Much easier - thanks for pointing this out.

>
> 1) name_show() above
>
> we could do :
> struct dev_ext_attribute *eattr = container_of(attr,
> struct dev_ext_attribute, attr);
>
> return scnprintf(bu, PAGE_SIZE, "0x%x\n", (u32)eattr->var);a

Casting with a u32 will make the compiler complain because of the size
difference between the types but using a cast type with the same size
will do just fine.

>
> 2) Matching the ID of a sink device in lookup by simply doing :
> (u32)csdev->dattr.var == (u32)(void *)data
>
> and can avoid computing the hash all the time.

Same comment as above but with the right cast it will work.

>
> > +
> > + if (csdev->type != CORESIGHT_DEV_TYPE_SINK &&
> > + csdev->type != CORESIGHT_DEV_TYPE_LINKSINK)
> > + return -EINVAL;
> > +
> > + if (csdev->dattr != NULL)
> > + return -EINVAL;
> > +
> > + if (!etm_perf_up)
> > + return -EPROBE_DEFER;
> > +
> > + dattr = kzalloc(sizeof(*dattr), GFP_KERNEL);
>
> nit: Could we use devm_kzalloc(pdev, ...) ?
>
> > + dattr->attr.name = kstrdup(dev_name(pdev), GFP_KERNEL);.
>
>
> similarly here : devm_kstrdup()

Yes

>
> > + dattr->attr.mode = 0444;
> > + dattr->show = etm_perf_sink_name_show;
> > + csdev->dattr = dattr;
> > +
> > + ret = sysfs_add_file_to_group(&pmu_dev->kobj,
> > + &dattr->attr, "sinks");
> > +
> > + if (!ret)
> > + return 0;
> > +
> > + csdev->dattr = NULL;
> > + kfree(dattr->attr.name);
> > + kfree(dattr);
>
> And we could get rid of these ^
>
> > +
> > + return ret;
> > +}
> > +
> > +void etm_perf_del_symlink_sink(struct coresight_device *csdev)
> > +{
> > + struct device *pmu_dev = etm_pmu.dev;
> > + struct device_attribute *dattr = csdev->dattr;
> > +
> > + if (csdev->type != CORESIGHT_DEV_TYPE_SINK &&
> > + csdev->type != CORESIGHT_DEV_TYPE_LINKSINK)
> > + return;
> > +
> > + if (!dattr)
> > + return;
> > +
> > + sysfs_remove_file_from_group(&pmu_dev->kobj,
> > + &dattr->attr, "sinks");
> > + csdev->dattr = NULL;
> > + kfree(dattr->attr.name);
> > + kfree(dattr);ext
>
> And these ^^
>
> > +}
>
>
> > diff --git a/include/linux/coresight.h b/include/linux/coresight.h
> > index 46c67a764877..a42fac83eac9 100644
> > --- a/include/linux/coresight.h
> > +++ b/include/linux/coresight.h
> > @@ -154,8 +154,9 @@ struct coresight_connection {
> > * @orphan: true if the component has connections that haven't been linked.
> > * @enable: 'true' if component is currently part of an active path.
> > * @activated: 'true' only if a _sink_ has been activated. A sink can be
> > - activated but not yet enabled. Enabling for a _sink_
> > - happens when a source has been selected for that it.
> > + * activated but not yet enabled. Enabling for a _sink_
> > + * appens when a source has been selected for that it.
> > + * @dattr: Device attribute for sink representation under PMU directory.
> > */
> > struct coresight_device {
> > struct coresight_connection *conns;
> > @@ -168,7 +169,9 @@ struct coresight_device {
> > atomic_t *refcnt;
> > bool orphan;
> > bool enable; /* true only if configured as part of a path */
> > + /* sink specific fields */
> > bool activated; /* true only if a sink is part of a path */
> > + struct device_attribute *dattr;
>
> See my comment above about switching to struct dev_ext_attribute *.
>
> Suzuki

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