Re: [PATCH] coresight: add support to enable more coresight paths

Hi

On 15/04/2021 10:33, Tao Zhang wrote:

Current coresight implementation only supports enabling source ETMs or STM. This patch adds support to enable more kinds of coresight source to sink paths. We build a path from source to sink when any source is enabled and store it in a list. When the source is disabled, we fetch the corresponding path from the list and decrement the refcount on each device in the path. The device is disabled if the refcount reaches zero. Don't store path to coresight data structure of source to avoid unnecessary change to ABI. Since some targets may have coresight sources other than STM and ETMs, we need to add this change to support these coresight devices.

While I am not against the patch, I would like to see why this change is needed. Which compnents are we talking about , other than STM / ETM ? Where is the "device" support code ? Without a legitimate user, we cannot add this change in.

Some other comments below.

Signed-off-by: Satyajit Desai sadesai@codeaurora.org Signed-off-by: Rama Aparna Mallavarapu aparnam@codeaurora.org Signed-off-by: Mulu He muluhe@codeaurora.org Signed-off-by: Tingwei Zhang tingwei@codeaurora.org Signed-off-by: Tao Zhang taozha@codeaurora.org

---

drivers/hwtracing/coresight/coresight-core.c | 101 +++++++++++++++------------ 1 file changed, 56 insertions(+), 45 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c index 4ba801d..7dfadb6 100644 --- a/drivers/hwtracing/coresight/coresight-core.c +++ b/drivers/hwtracing/coresight/coresight-core.c @@ -35,18 +35,16 @@ struct coresight_node { }; /*

• • When operating Coresight drivers from the sysFS interface, only a single
• • path can exist from a tracer (associated to a CPU) to a sink.

• • struct coresight_path - path from source to sink
• • @path: Address of path list.
• • @link: hook to the list.
  */

-static DEFINE_PER_CPU(struct list_head *, tracer_path); +struct coresight_path {

• struct list_head *path;
• struct list_head link;

+}; -/*

• • As of this writing only a single STM can be found in CS topologies. Since
• • there is no way to know if we'll ever see more and what kind of
• • configuration they will enact, for the time being only define a single path
• • for STM.
• */

-static struct list_head *stm_path; +static LIST_HEAD(cs_active_paths); /*

• When losing synchronisation a new barrier packet needs to be inserted at the

@@ -326,7 +324,7 @@ static void coresight_disable_sink(struct coresight_device *csdev) if (ret) return; coresight_control_assoc_ectdev(csdev, false);

• csdev->enable = false;

• csdev->activated = false; }

static int coresight_enable_link(struct coresight_device *csdev, @@ -562,6 +560,20 @@ int coresight_enable_path(struct list_head *path, u32 mode, void *sink_data) goto out; } +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;

+}

• struct coresight_device *coresight_get_sink(struct list_head *path) { struct coresight_device *csdev;

@@ -1047,9 +1059,23 @@ static int coresight_validate_source(struct coresight_device *csdev, return 0; } +static int coresight_store_path(struct list_head *path) +{

• struct coresight_path *node;
• node = kzalloc(sizeof(struct coresight_path), GFP_KERNEL);

Have you run this with all the "DEBUG" whistles turned on ? This could be problematic when called from a context where you are not allowed to sleep. e.g, perf enable call back.

• if (!node)

• return -ENOMEM;
  

• node->path = path;
• list_add(&node->link, &cs_active_paths);
• return 0;

+}

• int coresight_enable(struct coresight_device *csdev) {

• int cpu, ret = 0;

• int ret = 0; struct coresight_device *sink; struct list_head *path; enum coresight_dev_subtype_source subtype;

@@ -1094,25 +1120,9 @@ int coresight_enable(struct coresight_device *csdev) if (ret) goto err_source;

• switch (subtype) {
• case CORESIGHT_DEV_SUBTYPE_SOURCE_PROC:

• /*
  

•  * When working from sysFS it is important to keep track
  

•  * of the paths that were created so that they can be
  

•  * undone in 'coresight_disable()'.  Since there can only
  

•  * be a single session per tracer (when working from sysFS)
  

•  * a per-cpu variable will do just fine.
  

•  */
  

• cpu = source_ops(csdev)->cpu_id(csdev);
  

• per_cpu(tracer_path, cpu) = path;
  

• break;
  

• case CORESIGHT_DEV_SUBTYPE_SOURCE_SOFTWARE:

• stm_path = path;
  

• break;
  

• default:

• /* We can't be here */
  

• break;
  

• }

• ret = coresight_store_path(path);
• if (ret)

• goto err_source;
  

out: mutex_unlock(&coresight_mutex); @@ -1129,8 +1139,11 @@ EXPORT_SYMBOL_GPL(coresight_enable); void coresight_disable(struct coresight_device *csdev) {

• int cpu, ret;

• int ret; struct list_head *path = NULL;
• struct coresight_path *cspath = NULL;
• struct coresight_path *cspath_next = NULL;
• struct coresight_device *src_csdev = NULL;

mutex_lock(&coresight_mutex); @@ -1141,20 +1154,18 @@ void coresight_disable(struct coresight_device *csdev) if (!csdev->enable || !coresight_disable_source(csdev)) goto out;

• switch (csdev->subtype.source_subtype) {
• case CORESIGHT_DEV_SUBTYPE_SOURCE_PROC:

• cpu = source_ops(csdev)->cpu_id(csdev);
  

• path = per_cpu(tracer_path, cpu);
  

• per_cpu(tracer_path, cpu) = NULL;
  

• break;
  

• case CORESIGHT_DEV_SUBTYPE_SOURCE_SOFTWARE:

• path = stm_path;
  

• stm_path = NULL;
  

• break;
  

• default:

• /* We can't be here */
  

• break;
  

--> Cut here <---

• list_for_each_entry_safe(cspath, cspath_next, &cs_active_paths, link) {

• src_csdev = coresight_get_source(cspath->path);
  

• if (!src_csdev)
  

• 	continue;
  

• if (src_csdev == csdev) {
  

• 	path = cspath->path;
  

• 	list_del(&cspath->link);
  

• 	kfree(cspath);
  

• }
  

  }

Why not add the above to coresight_{retrieve/remove/}_active_path(csdev) ?

Suzuki