Received-SPF: pass (google.com: domain of linux-kernel+bounces-145262-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:4601:e00::3 as permitted sender) client-ip=2604:1380:4601:e00::3;
Message-ID: <7fc09bfe-b34a-4658-a141-105f0f62e62c@arm.com>
Date: Mon, 15 Apr 2024 14:24:05 +0100
Precedence: bulk
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH 2/4] coresight: Add support for multiple output ports on
 the funnel
Content-Language: en-GB
To: Tao Zhang <quic_taozha@quicinc.com>,
 Mathieu Poirier <mathieu.poirier@linaro.org>,
 Alexander Shishkin <alexander.shishkin@linux.intel.com>,
 Konrad Dybcio <konradybcio@gmail.com>, Mike Leach <mike.leach@linaro.org>,
 Rob Herring <robh+dt@kernel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>
Cc: Jinlong Mao <quic_jinlmao@quicinc.com>, Leo Yan <leo.yan@linaro.org>,
 Greg Kroah-Hartman <gregkh@linuxfoundation.org>, coresight@lists.linaro.org,
 linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
 devicetree@vger.kernel.org, Tingwei Zhang <quic_tingweiz@quicinc.com>,
 Yuanfang Zhang <quic_yuanfang@quicinc.com>,
 Trilok Soni <quic_tsoni@quicinc.com>, Song Chai <quic_songchai@quicinc.com>,
 linux-arm-msm@vger.kernel.org, andersson@kernel.org
References: <1711009927-17873-1-git-send-email-quic_taozha@quicinc.com>
 <1711009927-17873-3-git-send-email-quic_taozha@quicinc.com>
 <8d381e6e-9328-46ff-83fe-efbe5bb4363e@arm.com>
 <ffce4577-b0f9-4af3-a379-0385a02ddae8@quicinc.com>
 <a8947ac4-e251-47ba-b44a-6f4fc58f1aac@arm.com>
 <6baaff95-728b-4492-ae3e-00dedbb50fb0@quicinc.com>
From: Suzuki K Poulose <suzuki.poulose@arm.com>
In-Reply-To: <6baaff95-728b-4492-ae3e-00dedbb50fb0@quicinc.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit

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.

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@quicinc.com>
>>>>> ---
>>>>>   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;
>>>>
>>