RE: [PATCH 2/4] coresight: Add support for multiple output ports on the funnel

[Mike Leach]

Hi Suzuki

> -----Original Message-----
> From: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> Sent: Thursday, April 18, 2024 10:00 AM
> To: Mike Leach <mike.leach@xxxxxxxxxx>
> Cc: Tao Zhang <quic_taozha@xxxxxxxxxxx>; Mathieu Poirier
> <mathieu.poirier@xxxxxxxxxx>; Alexander Shishkin
> <alexander.shishkin@xxxxxxxxxxxxxxx>; Konrad Dybcio
> <konradybcio@xxxxxxxxx>; Rob Herring <robh+dt@xxxxxxxxxx>; Krzysztof
> Kozlowski <krzysztof.kozlowski+dt@xxxxxxxxxx>; Jinlong Mao
> <quic_jinlmao@xxxxxxxxxxx>; Greg Kroah-Hartman
> <gregkh@xxxxxxxxxxxxxxxxxxx>; coresight@xxxxxxxxxxxxxxxx; linux-arm-
> kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> devicetree@xxxxxxxxxxxxxxx; Tingwei Zhang <quic_tingweiz@xxxxxxxxxxx>;
> Yuanfang Zhang <quic_yuanfang@xxxxxxxxxxx>; Trilok Soni
> <quic_tsoni@xxxxxxxxxxx>; Song Chai <quic_songchai@xxxxxxxxxxx>; linux-arm-
> msm@xxxxxxxxxxxxxxx; andersson@xxxxxxxxxx
> Subject: Re: [PATCH 2/4] coresight: Add support for multiple output ports on the
> funnel
> 
> Hi Mike
> 
> On 18/04/2024 09:48, Mike Leach wrote:
> > Hi Suzuki
> >
> > On Wed, 17 Apr 2024 at 10:21, Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> wrote:
> >>
> >> Hi Mike
> >>
> >> On 16/04/2024 15:19, Mike Leach wrote:
> >>> Hi,
> >>>
> >>> On Mon, 15 Apr 2024 at 14:24, Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> wrote:
> >>>>
> >>>> On 09/04/2024 14:22, Tao Zhang wrote:
> >>>>>
> >>>>> On 4/9/2024 3:13 PM, Suzuki K Poulose wrote:
> >>>>>> Hi
> >>>>>>
> >>>>>> On 29/03/2024 09:27, Tao Zhang wrote:
> >>>>>>>
> >>>>>>> On 3/22/2024 12:41 AM, Suzuki K Poulose wrote:
> >>>>>>>> On 21/03/2024 08:32, Tao Zhang wrote:
> >>>>>>>>> Funnel devices are now capable of supporting multiple-inputs
> >>>>>>>>> and multiple-outputs configuration with in built hardware
> >>>>>>>>> filtering for TPDM devices. Add software support to this
> >>>>>>>>> function. Output port is selected according to the source in the trace
> path.
> >>>>>>>>>
> >>>>>>>>> The source of the input port on funnels will be marked in the
> >>>>>>>>> device tree.
> >>>>>>>>> e.g.
> >>>>>>>>> tpdm@xxxxxxx {
> >>>>>>>>>        ... ... ... ...
> >>>>>>>>> };
> >>>>>>>>>
> >>>>>>>>> funnel_XXX: funnel@xxxxxxx {
> >>>>>>>>>        ... ... ... ...
> >>>>>>>>>        out-ports {
> >>>>>>>>>            ... ... ... ...
> >>>>>>>>>            port@x {
> >>>>>>>>>                ... ... ... ...
> >>>>>>>>>                label = "xxxxxxx.tpdm"; <-- To label the source
> >>>>>>>>>            };                           corresponding to the output
> >>>>>>>>>        ... ... ... ...                  connection "port@x". And this
> >>>>>>>>>        };                               is a hardware static
> >>>>>>>>> connections.
> >>>>>>>>>        ... ... ... ...                  Here needs to refer to hardware
> >>>>>>>>> };                                   design.
> >>>>>>>>>
> >>>>>>>>> Then driver will parse the source label marked in the device
> >>>>>>>>> tree, and save it to the coresight path. When the function
> >>>>>>>>> needs to know the source label, it could obtain it from coresight path
> parameter.
> >>>>>>>>> Finally,
> >>>>>>>>> the output port knows which source it corresponds to, and it
> >>>>>>>>> also knows which input port it corresponds to.
> >>>>>>>>
> >>>>>>>> Why do we need labels ? We have connection information for all
> >>>>>>>> devices (both in and out), so, why do we need this label to find a device
> ?
> >>>>>>>
> >>>>>>> Because our funnel's design has multi-output ports, the data
> >>>>>>> stream will not
> >>>>>>>
> >>>>>>> know which output port should pass in building the data trace path.
> >>>>>>> This source
> >>>>>>>
> >>>>>>> label can make the data stream find the right output port to go.
> >>>>>>>
> >>>>>>>>
> >>>>>>>> And also, I thought TPDM is a source device, why does a funnel
> >>>>>>>> output port link to a source ?
> >>>>>>>
> >>>>>>> No, this label doesn't mean this funnel output port link to a
> >>>>>>> source, it just let
> >>>>>>>
> >>>>>>> the output port know its data source.
> >>>>>>>
> >>>>>>>>
> >>>>>>>> Are these funnels programmable ? Or, are they static ? If they
> >>>>>>>> are static, do these need to be described in the DT ? If they
> >>>>>>>> are simply acting as a "LINK" (or HWFIFO ?)
> >>>>>>>
> >>>>>>> These funnels are static, and we will add the "label" to the DT
> >>>>>>> to describe the
> >>>>>>>
> >>>>>>> multi-output ports for these funnels.
> >>>>>>
> >>>>>> I think there is still a bit of confusion. By "Dynamic" I mean,
> >>>>>> the "dynamic funnel" (explicit port enablement via MMIO) vs
> >>>>>> "static funnel" (no programming, always ON).
> >>>>>>
> >>>>>> So, coming to your example, do we need to "explicitly" enable
> >>>>>> trace flow for an "input" and/or an "output" port in your "funnel" ?
> >>>>>
> >>>>> Sorry for my misunderstanding in the previous mails. Our funnels
> >>>>> are programmable just like the common dynamic funnels.
> >>>>>
> >>>>> In our solution, we just make funnels have multiple output ports
> >>>>> connected to different devices or ports. When we use it, we still
> >>>>>
> >>>>> enable the input port through programming. Our solution is to know
> >>>>> which input port the expected data comes from based on the
> >>>>>
> >>>>> source label corresponding to the output port. This way we can
> >>>>> build the expected trace path. In other respects, it is used the
> >>>>> same
> >>>>>
> >>>>> as common dynamic funnels.
> >>>>
> >>>>
> >>>> Ok. So, to summarise :
> >>>>
> >>>> 1. This is not a standard Funnel, but a trace link with multiple-input
> >>>>       and multiple-output, with inputs hardwired to an outline at
> >>>>       integration.
> >>>> 2. The programming model is same as that of a "standard funnel".
> >>>>
> >>>> Now, we do have enough information in the coresight_connections to
> >>>> traverse input/output ports. But we need additional logic to
> >>>> "hardwire" the ports to each other and necessary logic to handle
> >>>> the
> >>>>
> >>>> There are two options here :
> >>>>
> >>>> 1. Treat this as a new component and have its own driver, with
> >>>>       additional logic to handle the input/output wiring.
> >>>>
> >>>> 2. Drive it using the funnel driver, with a a new compatible and
> >>>>       add additional logic to handle the input/output wiring.
> >>>>
> >>>> My inclination is towards (2), we need to see how this works out.
> >>>>
> >>>> We need to irrespective of the options, we need special handling
> >>>> for hardwired ports in 1) building path 2) walking back the path
> >>>> (in TPDA driver)
> >>>>
> >>>> We also need some "DT" information to bind a given input port to an
> >>>> output port. We must not use "any device" labels to hack this up,
> >>>> like the approach in this series.
> >>>>
> >>>
> >>> Given that the internal connections are static for the given device,
> >>> then the compatible will imply these connections in just the same
> >>> way as the arm,coresight-funnel implies that all inputs are
> >>> connected to the single output.
> >>
> >> I am sorry, I couldn't follow the last part. We have two or more
> >> output ports and we need a way to identify, which input port is
> >> hardwired to
> >> output-port0 and output-port1. Given we need special handling for
> >> these anyway, I would like to avoid hard coding the input-output connection.
> >> i.e., we do not want to assume that input-0  is always => output-0.
> >>
> >
> > If we regard the current component as having compatible
> > "qcom,coresight-compound-funnel-v1", then this identifies the
> > relationship between the in-ports and out-ports.
> > So the new driver / extension to the funnel driver that handles this
> > compatible with know the static mapping between input and output so
> > program it.
> 
> Ok, but like I said, having one compatible may not be enough to know the "static"
> mapping for all possible device instances on different SoCs.
> 

The compatible name would have to change if the mapping changed. 
Using the compatible is simpler, but less flexible

> >
> > If however you want a more generic approach to handle future different
> > versions of the component, then of course a method in DT of mapping
> > in-ports to out-ports is useful.
> >
> > If did wonder if something along the lines of:-
> >
> > compound-funnel@0x1234000 {
> >       compatible = "compound-funnel"
> >       regs = < 0x1234000 0x1000>
> >        sub-funnel@0 {
> >                   in-ports {
> >                          [some port definitions]
> >                    }
> >                   out-ports {
> >                         [some port definitions]
> >                    }
> >         }
> >        sub-funnel@1 {
> >                   in-ports {
> >                          [some port definitions]
> >                    }
> >                   out-ports {
> >                         [some port definitions]
> >                   }
> >          }
> > }
> 
> That would work, with "two" different coresight devices for each "embedded
> funnel". And that also confuses the user with the topology.

I wasn't suggesting two different coresight devices, but finding a way to iterate the sub-nodes to create a single device with the inputs mapped to outputs. Which may or may not be easily do-able.

As to topology - no more confusing than a "funnel" with multiple outputs, or phandle links between inputs and outputs. It does visually represent what the device really is - multiple effective funnels controlled by a single set of registers.

Mike

> 
> >
> >
> > might be made to work? not sure about the implications of having more
> > that one set of in-ports and out-ports in a component in the device
> > tree & would need specific handling in the driver to iterate
> > sub-funnels.
> >
> >
> >>
> >>>
> >>> Irrespective of if a new driver is used, or an extension to the
> >>> current funnel driver to handle a new compatible - the mapping
> >>> between input and output ports are created based on the compatible..
> >>>
> >>> As we are building a path from source to sink, what is then needed
> >>> is a method in the generic path building code, to recognise these
> >>> amppings and filter the output ports that are searched based on the
> >>> input port in use.
> >>
> >> Agreed. We could mark this as a property of the
> >> port/coresight_connection.
> >>
> >>>
> >>> On standard components, where the mapping is not present, then the
> >>> code will continue as it does now, for these compound funnels, the
> >>> mappings will be present and the output filtering will occur.
> >>
> >> Agreed
> >>
> >>> This removes the need for the labels / extra connection attributes
> >>> on devices other than the funnel, and also removes the need to
> >>> specify the internal connections as part of the device tree.
> >>
> >> I am still not clear how we map the input-output ports. Rest is what
> >> exactly I had in mind. So, once we sort out the port mapping we could
> >> proceed to the prototyping.
> >>
> >
> > given we iterate by output port index into an array of out ports, and
> > have an array of in-ports by index, a third mapping array, same size
> > as in-ports, determining the associated out port index should suffice.
> > Mapping array should be optional - if not there, path discovery works
> > as previously
> 
> We could simply add a "(sticky)flag" to the
> "coresight_connection".src_port/dest_port and extend the array to include the
> sticky_port for src/dest port and use that flag to force the path traversal.
> 
> Suzuki
> 
> 
> 
> >
> > Regards
> >
> > Mike
> >
> >> Kind regards
> >> Suzuki
> >>
> >>
> >>>
> >>> Regards
> >>>
> >>> Mike
> >>>
> >>>> Rob/Krzysztof,
> >>>>
> >>>> Do you have any recommendations for describing the 'hard wired
> >>>> ports' ?
> >>>>
> >>>> e.g:
> >>>>
> >>>> component {
> >>>>       input_ports {
> >>>>          component_input_port0: port@0 {
> >>>>              ...
> >>>>              <hard-wired-to*> = &component_output_port0;
> >>>>          };
> >>>>          ...
> >>>>      };
> >>>>
> >>>>      output_ports {
> >>>>        componentne_output_port0: port@0 {
> >>>>            ...
> >>>>            <hard-wired-to> = &component_input_port0;
> >>>>        };
> >>>>        ...
> >>>>      };
> >>>>
> >>>> };
> >>>>
> >>>> *Need a better suitable property than "hard-wired-to".
> >>>>
> >>>>
> >>>> Suzuki
> >>>>
> >>>>
> >>>>>
> >>>>>
> >>>>> Best,
> >>>>>
> >>>>> Tao
> >>>>>
> >>>>>>
> >>>>>>
> >>>>>>>
> >>>>>>> "If they are simply acting as a "LINK" (or HWFIFO ?) " I'm not
> >>>>>>> sure what's the meaning
> >>>>>>
> >>>>>> i.e, Like TMC-ETF in HWFIFO mode. In this mode, the TMC-ETF is
> >>>>>> acting like a cache for easing ATB data load, by providing h/w buffering.
> >>>>>> (In your case, it may not be providing any buffering, it doesn't
> >>>>>> matter either way, as it is not visible to the driver).
> >>>>>>
> >>>>>> Suzuki
> >>>>>>
> >>>>>>>
> >>>>>>> of this. Could you describe it in detail?
> >>>>>>>
> >>>>>>>
> >>>>>>> Best,
> >>>>>>>
> >>>>>>> Tao
> >>>>>>>
> >>>>>>>>
> >>>>>>>> Suzuki
> >>>>>>>>
> >>>>>>>>>
> >>>>>>>>> Signed-off-by: Tao Zhang <quic_taozha@xxxxxxxxxxx>
> >>>>>>>>> ---
> >>>>>>>>>     drivers/hwtracing/coresight/coresight-core.c  | 81
> >>>>>>>>> ++++++++++++++++---
> >>>>>>>>>     .../hwtracing/coresight/coresight-platform.c  |  5 ++
> >>>>>>>>>     include/linux/coresight.h                     |  2 +
> >>>>>>>>>     3 files changed, 75 insertions(+), 13 deletions(-)
> >>>>>>>>>
> >>>>>>>>> diff --git a/drivers/hwtracing/coresight/coresight-core.c
> >>>>>>>>> b/drivers/hwtracing/coresight/coresight-core.c
> >>>>>>>>> index 5dde597403b3..b1b5e6d9ec7a 100644
> >>>>>>>>> --- a/drivers/hwtracing/coresight/coresight-core.c
> >>>>>>>>> +++ b/drivers/hwtracing/coresight/coresight-core.c
> >>>>>>>>> @@ -113,15 +113,63 @@ struct coresight_device
> >>>>>>>>> *coresight_get_percpu_sink(int cpu)
> >>>>>>>>>     }
> >>>>>>>>>     EXPORT_SYMBOL_GPL(coresight_get_percpu_sink);
> >>>>>>>>>     +static struct coresight_device
> >>>>>>>>> *coresight_get_source(struct list_head *path)
> >>>>>>>>> +{
> >>>>>>>>> +    struct coresight_device *csdev;
> >>>>>>>>> +
> >>>>>>>>> +    if (!path)
> >>>>>>>>> +        return NULL;
> >>>>>>>>> +
> >>>>>>>>> +    csdev = list_first_entry(path, struct coresight_node,
> >>>>>>>>> link)->csdev;
> >>>>>>>>> +    if (csdev->type != CORESIGHT_DEV_TYPE_SOURCE)
> >>>>>>>>> +        return NULL;
> >>>>>>>>> +
> >>>>>>>>> +    return csdev;
> >>>>>>>>> +}
> >>>>>>>>> +
> >>>>>>>>> +/**
> >>>>>>>>> + * coresight_source_filter - checks whether the connection
> >>>>>>>>> +matches
> >>>>>>>>> the source
> >>>>>>>>> + * of path if connection is binded to specific source.
> >>>>>>>>> + * @path:    The list of devices
> >>>>>>>>> + * @conn:    The connection of one outport
> >>>>>>>>> + *
> >>>>>>>>> + * Return zero if the connection doesn't have a source binded
> >>>>>>>>> + or
> >>>>>>>>> source of the
> >>>>>>>>> + * path matches the source binds to connection.
> >>>>>>>>> + */
> >>>>>>>>> +static int coresight_source_filter(struct list_head *path,
> >>>>>>>>> +            struct coresight_connection *conn) {
> >>>>>>>>> +    int ret = 0;
> >>>>>>>>> +    struct coresight_device *source = NULL;
> >>>>>>>>> +
> >>>>>>>>> +    if (conn->source_label == NULL)
> >>>>>>>>> +        return ret;
> >>>>>>>>> +
> >>>>>>>>> +    source = coresight_get_source(path);
> >>>>>>>>> +    if (source == NULL)
> >>>>>>>>> +        return ret;
> >>>>>>>>> +
> >>>>>>>>> +    if (strstr(kobject_get_path(&source->dev.kobj, GFP_KERNEL),
> >>>>>>>>> +            conn->source_label))
> >>>>>>>>> +        ret = 0;
> >>>>>>>>> +    else
> >>>>>>>>> +        ret = -1;
> >>>>>>>>> +
> >>>>>>>>> +    return ret;
> >>>>>>>>> +}
> >>>>>>>>> +
> >>>>>>>>>     static struct coresight_connection *
> >>>>>>>>>     coresight_find_out_connection(struct coresight_device *src_dev,
> >>>>>>>>> -                  struct coresight_device *dest_dev)
> >>>>>>>>> +                  struct coresight_device *dest_dev,
> >>>>>>>>> +                  struct list_head *path)
> >>>>>>>>>     {
> >>>>>>>>>         int i;
> >>>>>>>>>         struct coresight_connection *conn;
> >>>>>>>>>           for (i = 0; i < src_dev->pdata->nr_outconns; i++) {
> >>>>>>>>>             conn = src_dev->pdata->out_conns[i];
> >>>>>>>>> +        if (coresight_source_filter(path, conn))
> >>>>>>>>> +            continue;
> >>>>>>>>>             if (conn->dest_dev == dest_dev)
> >>>>>>>>>                 return conn;
> >>>>>>>>>         }
> >>>>>>>>> @@ -312,7 +360,8 @@ static void coresight_disable_sink(struct
> >>>>>>>>> coresight_device *csdev)
> >>>>>>>>>       static int coresight_enable_link(struct coresight_device *csdev,
> >>>>>>>>>                      struct coresight_device *parent,
> >>>>>>>>> -                 struct coresight_device *child)
> >>>>>>>>> +                 struct coresight_device *child,
> >>>>>>>>> +                 struct list_head *path)
> >>>>>>>>>     {
> >>>>>>>>>         int ret = 0;
> >>>>>>>>>         int link_subtype;
> >>>>>>>>> @@ -321,8 +370,8 @@ static int coresight_enable_link(struct
> >>>>>>>>> coresight_device *csdev,
> >>>>>>>>>         if (!parent || !child)
> >>>>>>>>>             return -EINVAL;
> >>>>>>>>>     -    inconn = coresight_find_out_connection(parent, csdev);
> >>>>>>>>> -    outconn = coresight_find_out_connection(csdev, child);
> >>>>>>>>> +    inconn = coresight_find_out_connection(parent, csdev, path);
> >>>>>>>>> +    outconn = coresight_find_out_connection(csdev, child,
> >>>>>>>>> + path);
> >>>>>>>>>         link_subtype = csdev->subtype.link_subtype;
> >>>>>>>>>           if (link_subtype == CORESIGHT_DEV_SUBTYPE_LINK_MERG
> >>>>>>>>> &&
> >>>>>>>>> IS_ERR(inconn))
> >>>>>>>>> @@ -341,7 +390,8 @@ static int coresight_enable_link(struct
> >>>>>>>>> coresight_device *csdev,
> >>>>>>>>>       static void coresight_disable_link(struct coresight_device *csdev,
> >>>>>>>>>                        struct coresight_device *parent,
> >>>>>>>>> -                   struct coresight_device *child)
> >>>>>>>>> +                   struct coresight_device *child,
> >>>>>>>>> +                   struct list_head *path)
> >>>>>>>>>     {
> >>>>>>>>>         int i;
> >>>>>>>>>         int link_subtype;
> >>>>>>>>> @@ -350,8 +400,8 @@ static void coresight_disable_link(struct
> >>>>>>>>> coresight_device *csdev,
> >>>>>>>>>         if (!parent || !child)
> >>>>>>>>>             return;
> >>>>>>>>>     -    inconn = coresight_find_out_connection(parent, csdev);
> >>>>>>>>> -    outconn = coresight_find_out_connection(csdev, child);
> >>>>>>>>> +    inconn = coresight_find_out_connection(parent, csdev, path);
> >>>>>>>>> +    outconn = coresight_find_out_connection(csdev, child,
> >>>>>>>>> + path);
> >>>>>>>>>         link_subtype = csdev->subtype.link_subtype;
> >>>>>>>>>           if (link_ops(csdev)->disable) { @@ -507,7 +557,7 @@
> >>>>>>>>> static void coresight_disable_path_from(struct
> >>>>>>>>> list_head *path,
> >>>>>>>>>             case CORESIGHT_DEV_TYPE_LINK:
> >>>>>>>>>                 parent = list_prev_entry(nd, link)->csdev;
> >>>>>>>>>                 child = list_next_entry(nd, link)->csdev;
> >>>>>>>>> -            coresight_disable_link(csdev, parent, child);
> >>>>>>>>> +            coresight_disable_link(csdev, parent, child,
> >>>>>>>>> + path);
> >>>>>>>>>                 break;
> >>>>>>>>>             default:
> >>>>>>>>>                 break;
> >>>>>>>>> @@ -588,7 +638,7 @@ int coresight_enable_path(struct list_head
> >>>>>>>>> *path, enum cs_mode mode,
> >>>>>>>>>             case CORESIGHT_DEV_TYPE_LINK:
> >>>>>>>>>                 parent = list_prev_entry(nd, link)->csdev;
> >>>>>>>>>                 child = list_next_entry(nd, link)->csdev;
> >>>>>>>>> -            ret = coresight_enable_link(csdev, parent, child);
> >>>>>>>>> +            ret = coresight_enable_link(csdev, parent, child,
> >>>>>>>>> + path);
> >>>>>>>>>                 if (ret)
> >>>>>>>>>                     goto err;
> >>>>>>>>>                 break;
> >>>>>>>>> @@ -802,7 +852,8 @@ static void coresight_drop_device(struct
> >>>>>>>>> coresight_device *csdev)
> >>>>>>>>>      */
> >>>>>>>>>     static int _coresight_build_path(struct coresight_device *csdev,
> >>>>>>>>>                      struct coresight_device *sink,
> >>>>>>>>> -                 struct list_head *path)
> >>>>>>>>> +                 struct list_head *path,
> >>>>>>>>> +                 struct coresight_device *source)
> >>>>>>>>>     {
> >>>>>>>>>         int i, ret;
> >>>>>>>>>         bool found = false;
> >>>>>>>>> @@ -814,7 +865,7 @@ static int _coresight_build_path(struct
> >>>>>>>>> coresight_device *csdev,
> >>>>>>>>>           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) {
> >>>>>>>>> +        if (_coresight_build_path(sink, sink, path, source)
> >>>>>>>>> + == 0) {
> >>>>>>>>>                 found = true;
> >>>>>>>>>                 goto out;
> >>>>>>>>>             }
> >>>>>>>>> @@ -825,8 +876,12 @@ static int _coresight_build_path(struct
> >>>>>>>>> coresight_device *csdev,
> >>>>>>>>>             struct coresight_device *child_dev;
> >>>>>>>>>               child_dev =
> >>>>>>>>> csdev->pdata->out_conns[i]->dest_dev;
> >>>>>>>>> +        if (csdev->pdata->out_conns[i]->source_label &&
> >>>>>>>>> + !strstr(kobject_get_path(&source->dev.kobj, GFP_KERNEL),
> >>>>>>>>> + csdev->pdata->out_conns[i]->source_label))
> >>>>>>>>> +            continue;
> >>>>>>>>>             if (child_dev &&
> >>>>>>>>> -            _coresight_build_path(child_dev, sink, path) == 0) {
> >>>>>>>>> +            _coresight_build_path(child_dev, sink, path,
> >>>>>>>>> + source)
> >>>>>>>>> == 0) {
> >>>>>>>>>                 found = true;
> >>>>>>>>>                 break;
> >>>>>>>>>             }
> >>>>>>>>> @@ -871,7 +926,7 @@ struct list_head
> >>>>>>>>> *coresight_build_path(struct coresight_device *source,
> >>>>>>>>>           INIT_LIST_HEAD(path);
> >>>>>>>>>     -    rc = _coresight_build_path(source, sink, path);
> >>>>>>>>> +    rc = _coresight_build_path(source, sink, path, source);
> >>>>>>>>>         if (rc) {
> >>>>>>>>>             kfree(path);
> >>>>>>>>>             return ERR_PTR(rc); diff --git
> >>>>>>>>> a/drivers/hwtracing/coresight/coresight-platform.c
> >>>>>>>>> b/drivers/hwtracing/coresight/coresight-platform.c
> >>>>>>>>> index 9d550f5697fa..f553fb20966d 100644
> >>>>>>>>> --- a/drivers/hwtracing/coresight/coresight-platform.c
> >>>>>>>>> +++ b/drivers/hwtracing/coresight/coresight-platform.c
> >>>>>>>>> @@ -205,6 +205,7 @@ static int
> >>>>>>>>> of_coresight_parse_endpoint(struct
> >>>>>>>>> device *dev,
> >>>>>>>>>         struct fwnode_handle *rdev_fwnode;
> >>>>>>>>>         struct coresight_connection conn = {};
> >>>>>>>>>         struct coresight_connection *new_conn;
> >>>>>>>>> +    const char *label;
> >>>>>>>>>           do {
> >>>>>>>>>             /* Parse the local port details */ @@ -243,6
> >>>>>>>>> +244,10 @@ static int of_coresight_parse_endpoint(struct
> >>>>>>>>> device *dev,
> >>>>>>>>>             conn.dest_fwnode = fwnode_handle_get(rdev_fwnode);
> >>>>>>>>>             conn.dest_port = rendpoint.port;
> >>>>>>>>>     +        conn.source_label = NULL;
> >>>>>>>>> +        if (!of_property_read_string(ep, "label", &label))
> >>>>>>>>> +            conn.source_label = label;
> >>>>>>>>> +
> >>>>>>>>>             new_conn = coresight_add_out_conn(dev, pdata, &conn);
> >>>>>>>>>             if (IS_ERR_VALUE(new_conn)) {
> >>>>>>>>>                 fwnode_handle_put(conn.dest_fwnode);
> >>>>>>>>> diff --git a/include/linux/coresight.h
> >>>>>>>>> b/include/linux/coresight.h index e8b6e388218c..a9c06ef9bbb2
> >>>>>>>>> 100644
> >>>>>>>>> --- a/include/linux/coresight.h
> >>>>>>>>> +++ b/include/linux/coresight.h
> >>>>>>>>> @@ -167,6 +167,7 @@ struct coresight_desc {
> >>>>>>>>>      * struct coresight_connection - representation of a
> >>>>>>>>> single connection
> >>>>>>>>>      * @src_port:    a connection's output port number.
> >>>>>>>>>      * @dest_port:    destination's input port number @src_port is
> >>>>>>>>> connected to.
> >>>>>>>>> + * @source_label: source component's label.
> >>>>>>>>>      * @dest_fwnode: destination component's fwnode handle.
> >>>>>>>>>      * @dest_dev:    a @coresight_device representation of the
> component
> >>>>>>>>>             connected to @src_port. NULL until the device is
> >>>>>>>>> created @@ -195,6 +196,7 @@ struct coresight_desc {
> >>>>>>>>>     struct coresight_connection {
> >>>>>>>>>         int src_port;
> >>>>>>>>>         int dest_port;
> >>>>>>>>> +    const char *source_label;
> >>>>>>>>>         struct fwnode_handle *dest_fwnode;
> >>>>>>>>>         struct coresight_device *dest_dev;
> >>>>>>>>>         struct coresight_sysfs_link *link;
> >>>>>>>>
> >>>>>>
> >>>>
> >>>
> >>>
> >>
> >
> >
> 
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