Re: [PATCH v5 08/14] coresight: cti: Enable CTI associated with devices.

[Mathieu Poirier <mathieu.poirier@linaro.org>]

On Fri, 29 Nov 2019 at 11:28, Suzuki Kuruppassery Poulose
<suzuki.poulose@arm.com> wrote:
>
> On 19/11/2019 23:19, Mike Leach wrote:
> > The CoreSight subsystem enables a path of devices from source to sink.
> > Any CTI devices associated with the path devices must be enabled at the
> > same time.
> >
> > This patch adds an associated coresight_device element to the main
> > coresight device structure, and uses this to create associations between
> > the CTI and other devices based on the device tree data. The associated
> > device element is used to enable CTI in conjunction with the path elements.
> >
> > CTI devices are reference counted so where a single CTI is associated with
> > multiple elements on the path, it will be enabled on the first associated
> > device enable, and disabled with the last associated device disable.
> >
> > Signed-off-by: Mike Leach <mike.leach@linaro.org>
> > ---
> >   drivers/hwtracing/coresight/coresight-cti.c   | 87 +++++++++++++++++++
> >   .../hwtracing/coresight/coresight-platform.c  | 23 +++++
> >   drivers/hwtracing/coresight/coresight-priv.h  |  6 ++
> >   drivers/hwtracing/coresight/coresight.c       | 58 +++++++++++--
> >   include/linux/coresight.h                     |  5 ++
> >   5 files changed, 173 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/hwtracing/coresight/coresight-cti.c b/drivers/hwtracing/coresight/coresight-cti.c
> > index 369488dd7b8e..cf116463149a 100644
> > --- a/drivers/hwtracing/coresight/coresight-cti.c
> > +++ b/drivers/hwtracing/coresight/coresight-cti.c
> > @@ -440,6 +440,90 @@ int cti_channel_setop(struct device *dev, enum cti_chan_set_op op,
> >       return err;
> >   }
> >
> > +/*
> > + * Look for a matching connection device name in the list of
> > + * connections. If found then swap in the csdev name and return
> > + * found.
> > + */
> > +static bool
> > +cti_match_con_name(struct cti_device *ctidev, const char *node_name,
> > +                const char *csdev_name)
>
> Here we actually fixup the name of the connection, rather than simply
> matching it. So it may be apt to rename this to cti_match_fixup_name()
>
> > +{
> > +     struct cti_trig_con *trig_con;
> > +
> > +     list_for_each_entry(trig_con, &ctidev->trig_cons, node) {
> > +             if (trig_con->con_dev_name) {
> > +                     if (!strcmp(node_name, trig_con->con_dev_name)) {
>
> Can there be duplicate node_name's ? Does it make sense to store the
> fwhandle along with the "temporary node_name" to match it later while
> fixing up ?

I think we're fine here - CS devices have bidirectional connections
that are checked by the DTC.  You get a bitter complaint if two CS
nodes have the same value.

>
> > +                             /* match: so swap in csdev name */
> > +                             kfree(trig_con->con_dev_name);
> > +                             trig_con->con_dev_name =
> > +                                     kstrdup(csdev_name, GFP_KERNEL);
> > +                             return true;
> > +                     }
> > +             }
> > +     }
> > +     return false;
> > +}
>
>
> > +/*
> > + * Search the cti list to add an associated CTI into the supplied CS device
> > + * This will set the association if CTI declared before the CS device
> > + */
> > +void cti_add_assoc_to_csdev(struct coresight_device *csdev)
> > +{
>
> ..
>
>  > +    struct cti_drvdata *ect_item;
>  > +    struct cti_device *ctidev;
>  > +    const char *node_name = NULL, *csdev_name;
>  > +
>  > +    /* protect the list */
>  > +    mutex_lock(&ect_mutex);
>  > +
>  > +    /* exit if current is an ECT device.*/
>  > +    if ((csdev->type == CORESIGHT_DEV_TYPE_ECT) || list_empty(&ect_net))
>  > +            goto cti_add_done;
>  > +
>  > +    /* if we didn't find the csdev previously we used the fwnode name */
>  > +    node_name = coresight_get_fwnode_name(csdev->dev.parent);
>
> We used "cti_plat_get_node_name()" when we added the name in the
> absence of csdev in patch 7, could we not reuse the function here ?
>
>  > +
>  > +    if (!node_name)
>  > +            goto cti_add_done;
>  > +
>  > +    /* this is the name we want to use for the association */
>  > +    csdev_name = dev_name(&csdev->dev);
>
>
> > +
> > +     /* for each CTI in list... */
> > +     list_for_each_entry(ect_item, &ect_net, node) {
> > +             ctidev = &ect_item->ctidev;
> > +             if (cti_match_con_name(ctidev, node_name, csdev_name)) {
> > +                     /*
> > +                      * if we found a matching name then update the
> > +                      * association pointers.
> > +                      */
> > +                     csdev->ect_dev = ect_item->csdev;
> > +                     goto cti_add_done;
>
>                         break; instead ?
>
> > +             }
> > +     }
> > +cti_add_done:
> > +     mutex_unlock(&ect_mutex);
> > +}
> > +EXPORT_SYMBOL_GPL(cti_add_assoc_to_csdev);
> > +
> > +/*
> > + * Update the cross references where the associated device was found
> > + * while we were building the connection info. This will occur if the
> > + * assoc device was registered before the CTI.
> > + */
> > +static void cti_update_conn_xrefs(struct cti_drvdata *drvdata)
> > +{
> > +     struct cti_trig_con *tc;
> > +     struct cti_device *ctidev = &drvdata->ctidev;
> > +
> > +     list_for_each_entry(tc, &ctidev->trig_cons, node) {
> > +             if (tc->con_dev)
> > +                     tc->con_dev->ect_dev = drvdata->csdev;
> > +     }
>
> Does this need to take the coresight_mutex to avoid racing against
> a coresight_enable_path() ? Though this may be fine as long as the
> CTI driver detects that that device was not enabled.
>
> Also, it looks like we have a potential issue with perf vs sysfs mode.
> The perf mode doesn't seem to take the coresight_mutex, for
> build_path/enable_path operations. This is outside the scope of this
> series though.
>
> > +}
> > +
> >   /** cti ect operations **/
> >   int cti_enable(struct coresight_device *csdev)
> >   {
> > @@ -574,6 +658,9 @@ static int cti_probe(struct amba_device *adev, const struct amba_id *id)
> >       drvdata->csdev_release = drvdata->csdev->dev.release;
> >       drvdata->csdev->dev.release = cti_device_release;
> >
> > +     /* set any cross references */
> > +     cti_update_conn_xrefs(drvdata);
> > +
>         /* all done - dec pm refcount */
> >       pm_runtime_put(&adev->dev);
> >       dev_info(&drvdata->csdev->dev, "CTI initialized\n");
> > diff --git a/drivers/hwtracing/coresight/coresight-platform.c b/drivers/hwtracing/coresight/coresight-platform.c
> > index 3c5bee429105..6721cb1af5fe 100644
> > --- a/drivers/hwtracing/coresight/coresight-platform.c
> > +++ b/drivers/hwtracing/coresight/coresight-platform.c
> > @@ -293,6 +293,12 @@ static int of_get_coresight_platform_data(struct device *dev,
> >
> >       return 0;
> >   }
> > +
> > +static inline const char *of_coresight_get_node_name(struct device *dev)
> > +{
> > +     return dev->of_node->full_name;
> > +}
> > +
> >   #else
> >   static inline int
> >   of_get_coresight_platform_data(struct device *dev,
> > @@ -305,6 +311,11 @@ static inline int of_coresight_get_cpu(struct device *dev)
> >   {
> >       return -ENODEV;
> >   }
> > +
> > +static inline const char *of_coresight_get_node_name(struct device *dev)
> > +{
> > +     return NULL;
> > +}
> >   #endif
> >
> >   #ifdef CONFIG_ACPI
> > @@ -766,6 +777,18 @@ static inline int acpi_coresight_get_cpu(struct device *dev)
> >   }
> >   #endif
> >
> > +const char *coresight_get_fwnode_name(struct device *dev)
>
> As mentioned above, please could we reuse the name helper we used
> during the insertion rather than introducing a new wrapper which
> effectively does the same thing ?
>
> > +{
> > +     const char *node_name = NULL;
> > +     struct fwnode_handle *fwnode = dev_fwnode(dev);
> > +
> > +     if (is_of_node(fwnode))
> > +             node_name = of_coresight_get_node_name(dev);
> > +
> > +     return node_name;
> > +}
> > +EXPORT_SYMBOL_GPL(coresight_get_fwnode_name);
>
> Why does this get exported ? If a following patch needs it, you may
> always do that when you need it.
>
>
> Cheers
> Suzuki