Message-ID: <db875eb9-9000-4e05-b955-866acda2f6a6@arm.com>
Date: Fri, 9 Aug 2024 12:00:35 +0100
From: Suzuki K Poulose <suzuki.poulose@....com>
To: Tao Zhang <quic_taozha@...cinc.com>, Mike Leach <mike.leach@...aro.org>,
 James Clark <james.clark@....com>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Mathieu Poirier <mathieu.poirier@...aro.org>,
 Leo Yan <leo.yan@...ux.dev>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
 linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v2 2/3] coresight: Add source filtering for multi-port
 output

On 09/08/2024 11:21, Tao Zhang wrote:
> 
> On 7/11/2024 9:05 PM, Suzuki K Poulose wrote:
>> On 11/07/2024 09:17, Tao Zhang wrote:
>>> In order to enable the output ports of multi-port output devices,
>>
>> This has nothing to do with multi-port. You wanted to pain the picture
>> of a multi-port device, while the reality is different.
>>
>>> such as static replicator, to correspond to designated sources,
>>> a mechanism for filtering data sources is introduced for the
>>> output ports.
>>>
>>> The specified source will be marked like below in the Devicetree.
>>> test-replicator {
>>>      ... ... ... ...
>>>      out-ports {
>>>          ... ... ... ...
>>>          port@0 {
>>>              reg = <0>;
>>>              xxx: endpoint {
>>>                  remote-endpoint = <&xxx>;
>>>                  filter_src = <&xxx>; <-- To specify the source to
>>>              };                           be filtered out here.
>>>          };
>>>
>>>          port@1 {
>>>              reg = <1>;
>>>              yyy: endpoint {
>>>                  remote-endpoint = <&yyy>;
>>>                  filter_src = <&yyy>; <-- To specify the source to
>>>              };                           be filtered out here.
>>>          };
>>>      };
>>> };
>>>
>>> Then driver will find the expected source marked in the Devicetree, and
>>> save it to the coresight path. When the function needs to filter the
>>> source, 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.
>>
>> Minor nit: I think the commit description is full of "How" you are 
>> doing something, while it must rather be: "What and Why?"
>>
>> I would prefer something like :
>>
>> Subject: coresight: Add support for trace filtering by source
>>
>> Some replicators have hard coded filtering of "trace" data, based on the
>> source device. This is different from the trace filtering based on
>> TraceID, available in the standard programmable replicators. e.g.,
>> Qualcomm replicators have filtering based on custom trace protocol
>> format and is not programmable.
>>
>> The source device could be connected to the replicator via intermediate
>> components (e.g., a funnel). Thus we need platform information from
>> the firmware tables to decide the source device corresponding to a
>> given output port from the replicator. Given this affects "trace
>> path building" and traversing the path back from the sink to source,
>> add the concept of "filtering by source" to the generic coresight
>> connection.
>>
>>
>>>
>>> Signed-off-by: Tao Zhang <quic_taozha@...cinc.com>
>>> ---
>>>   drivers/hwtracing/coresight/coresight-core.c  | 125 ++++++++++++++++--
>>>   .../hwtracing/coresight/coresight-platform.c  |  18 +++
>>>   include/linux/coresight.h                     |   5 +
>>>   3 files changed, 135 insertions(+), 13 deletions(-)
>>>
>>> diff --git a/drivers/hwtracing/coresight/coresight-core.c 
>>> b/drivers/hwtracing/coresight/coresight-core.c
>>> index 9fc6f6b863e0..3f02a31b9328 100644
>>> --- a/drivers/hwtracing/coresight/coresight-core.c
>>> +++ b/drivers/hwtracing/coresight/coresight-core.c
>>> @@ -75,15 +75,60 @@ 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;
>>> +}
>>> +
>>
>> Why is this still here ? Didn't agree to remove this and pass the source
>> directly ?
> 
> I would like to discuss with you about passing the "source" directly. 
> Since the APIs "coresight_enable_path" and
> 
> "coresight_disable_path" are called in coresight-etm-perf.c as well. If 
> passing the "source" to them directly, I need to
> 
> modify the code in coresight-etm-perf.c as well. In order to reduce the 
> modification, how about if I keep using
> 
> "coresight_get_source" in "coresight_enable_path" and 
> "coresight_disable_path" to get "source" for filtering
> 
> the source in "coresight_block_source"?

Yes, please retain the helper. The above comment was based on my
"bad memory" of disable_path_from() was called with a partial path.

No need to change the function. Once again, apologies for the confusion.

Suzuki



> 
> 
> Best,
> 
> Tao
> 
>>
>>> +/**
>>> + * coresight_source_filter - checks whether the connection matches 
>>> the source
>>> + * of path if connection is binded to specific source.
>>> + * @trace_source: The source device of the trace path
>>> + * @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 coresight_device 
>>> *trace_source,
>>> +            struct coresight_connection *conn)
>>
>> This name is a bit confusing. It doesn't tell you, whether it
>> allows the trace or blocks it.
>>
>>> +{
>>> +    int ret = 0;
>>> +
>>> +    if (!conn->filter_src_dev)
>>> +        return ret;
>>
>> This is not the correct check. It must be :
>>
>> if (!conn->filter_src_fwnode)
>>
>> Because, the device could have disappeared (or not appeared yet). 
>> e.g., (TPDM) driver module unloaded/not - loaded.
>>
>>> +
>>> +    if (!trace_source)
>>
>> Is that possible ?
>>
>>> +        return -1;
>>> +
>>> +    if (conn->filter_src_dev == trace_source)
>>> +        ret = 0;
>>> +    else
>>> +        ret = -1;
>>
>> Couldn't this simply be :
>>
>> /*
>>  * Returns true, if the trace path is not possible through @conn
>>  * for trace originating from @src
>>  */
>> static bool coresight_blocks_source(src, conn)
>> {
>>     return conn->filter_src_fwnode &&
>>         (conn->filter_src_dev != src);
>> }
>>
>>> +
>>> +    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 coresight_device *trace_source)
>>
>> Please could you rename :
>>
>>     src_dev => csdev
>>     dest_dev => out_dev
>>     trace_source => trace_src ?
>>
>> Having src_dev and trace_source in the same list is confusing.
>>
>>>   {
>>>       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(trace_source, conn))
>>
>>         if (coresight_blocks_source(trace_source, conn))
>>             continue;
>>
>>> +            continue;
>>>           if (conn->dest_dev == dest_dev)
>>>               return conn;
>>>       }
>>> @@ -251,7 +296,8 @@ 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 coresight_device *trace_source)
>>>   {
>>>       int link_subtype;
>>>       struct coresight_connection *inconn, *outconn;
>>> @@ -259,8 +305,8 @@ 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, 
>>> trace_source);
>>> +    outconn = coresight_find_out_connection(csdev, child, 
>>> trace_source);
>>>       link_subtype = csdev->subtype.link_subtype;
>>>         if (link_subtype == CORESIGHT_DEV_SUBTYPE_LINK_MERG && 
>>> IS_ERR(inconn))
>>> @@ -273,15 +319,16 @@ 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 coresight_device *trace_source)
>>>   {
>>>       struct coresight_connection *inconn, *outconn;
>>>         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, 
>>> trace_source);
>>> +    outconn = coresight_find_out_connection(csdev, child, 
>>> trace_source);
>>>         link_ops(csdev)->disable(csdev, inconn, outconn);
>>>   }
>>> @@ -341,6 +388,9 @@ static void coresight_disable_path_from(struct 
>>> list_head *path,
>>>   {
>>>       u32 type;
>>>       struct coresight_device *csdev, *parent, *child;
>>> +    struct coresight_device *source;
>>> +
>>> +    source = coresight_get_source(path);
>>
>> Grr! This must come from the "caller of the 
>> coresight_disable_path_from()", which was my comment. Please go back
>> and double check the comment on previous version.
>>
>>
>>>         if (!nd)
>>>           nd = list_first_entry(path, struct coresight_node, link);
>>> @@ -375,7 +425,7 @@ 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, source);
>>>               break;
>>>           default:
>>>               break;
>>> @@ -418,6 +468,9 @@ int coresight_enable_path(struct list_head *path, 
>>> enum cs_mode mode,
>>>       u32 type;
>>>       struct coresight_node *nd;
>>>       struct coresight_device *csdev, *parent, *child;
>>> +    struct coresight_device *source;
>>> +
>>> +    source = coresight_get_source(path);
>>>         list_for_each_entry_reverse(nd, path, link) {
>>>           csdev = nd->csdev;
>>> @@ -456,7 +509,7 @@ 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, source);
>>>               if (ret)
>>>                   goto err;
>>>               break;
>>> @@ -619,6 +672,7 @@ static void coresight_drop_device(struct 
>>> coresight_device *csdev)
>>>    * @csdev:    The device to start from.
>>>    * @sink:    The final sink we want in this path.
>>>    * @path:    The list to add devices to.
>>> + * @trace_source: The trace source device of the path.
>>>    *
>>>    * The tree of Coresight device is traversed until @sink is found.
>>>    * From there the sink is added to the list along with all the 
>>> devices that led
>>> @@ -627,7 +681,8 @@ 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 *trace_source)
>>>   {
>>>       int i, ret;
>>>       bool found = false;
>>> @@ -639,7 +694,7 @@ 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, trace_source) == 
>>> 0) {
>>>               found = true;
>>>               goto out;
>>>           }
>>> @@ -650,8 +705,13 @@ 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]->filter_src_dev
>>> +            && (csdev->pdata->out_conns[i]->filter_src_dev != 
>>> trace_source))
>>> +            continue;
>>> +
>>>           if (child_dev &&
>>> -            _coresight_build_path(child_dev, sink, path) == 0) {
>>> +            _coresight_build_path(child_dev, sink, path, 
>>> trace_source) == 0) {
>>>               found = true;
>>>               break;
>>>           }
>>> @@ -696,7 +756,7 @@ 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);
>>> @@ -957,6 +1017,14 @@ static int coresight_orphan_match(struct device 
>>> *dev, void *data)
>>>               /* This component still has an orphan */
>>>               still_orphan = true;
>>>           }
>>
>>
>>> +        if ((conn->filter_src_fwnode) && dst_csdev
>>> +            && (conn->filter_src_fwnode == dst_csdev->dev.fwnode)) {
>>> +            conn->filter_src_dev = dst_csdev;
>>> +            if (conn->filter_src_dev->type
>>> +                != CORESIGHT_DEV_TYPE_SOURCE)
>>> +                dev_warn(&conn->filter_src_dev->dev,
>>> +                  "Filter source is not a source device\n");
>>> +        }
>>
>> Have you tested your code with the following order :
>>
>> 1) Build everything as module
>> 2) Load the replicator driver.
>> 3) Load the TPDM driver
>>
>> And are you able to get the trace working ? I suspect it doesn't work. 
>> The csdev->orphan must be used to track if there is any missing link
>> with unresolved "filter_src_dev".
>>
>>
>>>       }
>>>         src_csdev->orphan = still_orphan;
>>> @@ -974,6 +1042,30 @@ static int coresight_fixup_orphan_conns(struct 
>>> coresight_device *csdev)
>>>                csdev, coresight_orphan_match);
>>>   }
>>>   +/* reset_filter_src - Reset the filter source if the source is 
>>> being removed */
>>> +static int reset_filter_src(struct coresight_device *trace_source,
>>> +                struct coresight_connection *conn)
>>> +{
>>> +    int i;
>>> +    int ret = -1;
>>> +    struct coresight_device *csdev;
>>> +    struct coresight_connection *output_conn;
>>
>> I don't think this is sufficient. I would rather walk through the 
>> entire coresight bus and fixup the filter_src_dev, rather than 
>> traversing the
>> paths. e.g., one of the devices in the path could have been removed.
>> See coresight_clear_default_sink() for e.g. You should have something
>> similar :
>>
>> coresight_clear_filter_source();
>>
>>
>> Suzuki
>>
>>
>>
>>> +
>>> +    csdev = conn->dest_dev;
>>> +    for (i = 0; i < csdev->pdata->nr_outconns; i++) {
>>> +        output_conn = csdev->pdata->out_conns[i];
>>> +        if (output_conn->filter_src_dev
>>> +            && (output_conn->filter_src_dev == trace_source)) {
>>> +            output_conn->filter_src_dev = NULL;
>>> +            return 0;
>>> +        }
>>> +        ret = reset_filter_src(trace_source, output_conn);
>>> +        if (!ret)
>>> +            return ret;
>>> +    }
>>> +    return ret;
>>> +}
>>> +
>>>   /* coresight_remove_conns - Remove other device's references to 
>>> this device */
>>>   static void coresight_remove_conns(struct coresight_device *csdev)
>>>   {
>>> @@ -986,6 +1078,13 @@ static void coresight_remove_conns(struct 
>>> coresight_device *csdev)
>>>        */
>>
>>
>>>       for (i = 0; i < csdev->pdata->nr_outconns; i++) {
>>>           conn = csdev->pdata->out_conns[i];
>>> +        if (csdev->type == CORESIGHT_DEV_TYPE_SOURCE)
>>> +            reset_filter_src(csdev, conn);
>>> +        if (conn->filter_src_fwnode) {
>>> +            conn->filter_src_dev = NULL;
>>> +            conn->filter_src_fwnode = NULL;
>>> +        }
>>> +
>>>           if (!conn->dest_dev)
>>>               continue;
>>>   diff --git a/drivers/hwtracing/coresight/coresight-platform.c 
>>> b/drivers/hwtracing/coresight/coresight-platform.c
>>> index 64e171eaad82..b3c3e2361d07 100644
>>> --- a/drivers/hwtracing/coresight/coresight-platform.c
>>> +++ b/drivers/hwtracing/coresight/coresight-platform.c
>>> @@ -243,6 +243,24 @@ static int of_coresight_parse_endpoint(struct 
>>> device *dev,
>>>           conn.dest_fwnode = fwnode_handle_get(rdev_fwnode);
>>>           conn.dest_port = rendpoint.port;
>>>   +        /*
>>> +         * Get the firmware node of the filter source through the
>>> +         * reference. This could be used to filter the source in
>>> +         * building path.
>>> +         */
>>> +        conn.filter_src_fwnode =
>>> +            fwnode_find_reference(&ep->fwnode, "filter-src", 0);
>>> +        if (IS_ERR(conn.filter_src_fwnode))
>>> +            conn.filter_src_fwnode = NULL;
>>> +        else {
>>> +            conn.filter_src_dev =
>>> + coresight_find_csdev_by_fwnode(conn.filter_src_fwnode);
>>> +            if (conn.filter_src_dev && (conn.filter_src_dev->type
>>> +                != CORESIGHT_DEV_TYPE_SOURCE))
>>> +                dev_warn(&conn.filter_src_dev->dev,
>>> +                  "Filter source %s is not a source device\n");
>>> +        }
>>> +
>>>           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 f09ace92176e..91a689b4514b 100644
>>> --- a/include/linux/coresight.h
>>> +++ b/include/linux/coresight.h
>>> @@ -172,6 +172,9 @@ struct coresight_desc {
>>>    * @dest_dev:    a @coresight_device representation of the component
>>>           connected to @src_port. NULL until the device is created
>>>    * @link: Representation of the connection as a sysfs link.
>>> + * @filter_src_fwnode: filter source component's fwnode handle.
>>> + * @filter_src_dev: a @coresight_device representation of the 
>>> component that
>>> +        needs to be filtered.
>>>    *
>>>    * The full connection structure looks like this, where in_conns store
>>>    * references to same connection as the source device's out_conns.
>>> @@ -200,6 +203,8 @@ struct coresight_connection {
>>>       struct coresight_device *dest_dev;
>>>       struct coresight_sysfs_link *link;
>>>       struct coresight_device *src_dev;
>>> +    struct fwnode_handle *filter_src_fwnode;
>>> +    struct coresight_device *filter_src_dev;
>>>       atomic_t src_refcnt;
>>>       atomic_t dest_refcnt;
>>>   };
>>

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