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Message-ID: <1f9609fe-298f-4a5f-aa5e-be8c7dd6a719@arm.com>
Date: Wed, 17 Apr 2024 10:21:08 +0100
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Subject: Re: [PATCH 2/4] coresight: Add support for multiple output ports on
 the funnel
To: Mike Leach <mike.leach@linaro.org>
Cc: Tao Zhang <quic_taozha@quicinc.com>,
 Mathieu Poirier <mathieu.poirier@linaro.org>,
 Alexander Shishkin <alexander.shishkin@linux.intel.com>,
 Konrad Dybcio <konradybcio@gmail.com>, Rob Herring <robh+dt@kernel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
 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>
 <7fc09bfe-b34a-4658-a141-105f0f62e62c@arm.com>
 <CAJ9a7VjP_B8o4krdZcz3J9qzUMSYmvVyy4cFyrYZOdg43YD2YA@mail.gmail.com>
Content-Language: en-US
From: Suzuki K Poulose <suzuki.poulose@arm.com>
In-Reply-To: <CAJ9a7VjP_B8o4krdZcz3J9qzUMSYmvVyy4cFyrYZOdg43YD2YA@mail.gmail.com>
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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@arm.com> 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.


> 
> 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.

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@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;
>>>>>>
>>>>
>>
> 
>