Re: [PATCH 01/10] coresight: add support to enable more coresight paths
From: Jinlong Mao
Date: Mon Nov 22 2021 - 10:12:14 EST
Hi Mathieu,
Thanks for the comments.
I double checked the code. Please see my comments below.
On 10/29/2021 2:06 AM, Mathieu Poirier wrote:
On Thu, Oct 21, 2021 at 03:38:47PM +0800, 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.
Signed-off-by: Tingwei Zhang <tingwei@xxxxxxxxxxxxxx>
Signed-off-by: Tao Zhang <quic_taozha@xxxxxxxxxxx>
---
drivers/hwtracing/coresight/coresight-core.c | 100 +++++++++++--------
1 file changed, 56 insertions(+), 44 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
index 8a18c71df37a..1e621d61307a 100644
--- a/drivers/hwtracing/coresight/coresight-core.c
+++ b/drivers/hwtracing/coresight/coresight-core.c
@@ -37,18 +37,16 @@ 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;
+};
For sources associated with a CPU, like ETMs, having a per-cpu way of storing
paths is a definite advantage and should be kept that way.
Hi Mathieu,
Could you please share what is the advantage to handle the sources
associated with a CPU separatly ?
From the code, cpu id is only used to get the path of the ETM source.
As there will be many tpdm sources, I think it will be easier to only
maintain one list for all the sources.
-/*
- * 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);
Then there are sources that aren't associated with a CPU like STMs and TPDMs.
Perhaps using an IDR or the hash of the device name as a key to a hashing
vector would be better than doing a sequential search, especially as the
list of devices is bound to increase over time.
Agree with you. I will try to use IDR or the hash of the device name as
a key to a hashing vector.
/*
* When losing synchronisation a new barrier packet needs to be inserted at the
@@ -354,6 +352,7 @@ static void coresight_disable_sink(struct coresight_device *csdev)
if (ret)
return;
coresight_control_assoc_ectdev(csdev, false);
+ csdev->activated = false;
I don't see why this is needed and without proper documentation there is no way
for me to guess the logic behind the change. The ->activated flag should be
manipulated from the command line interface only.
When source is disabled, but sink is still actived. It will be confused
for end users.
csdev->enable = false;
}
@@ -590,6 +589,20 @@ 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;
@@ -1086,9 +1099,23 @@ 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);
+ 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;
@@ -1133,25 +1160,9 @@ 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);
@@ -1168,8 +1179,11 @@ 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);
@@ -1180,20 +1194,18 @@ 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;
+ 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);
See my comment above - I agree that sources _not_ associated with a CPU should
be handled differently. CPU bound sources should be kept untouched.
That is all the time I had for today, I will continue tomorrow.
Thanks,
Mathieu
+ }
}
+ if (path == NULL)
+ goto out;
coresight_disable_path(path);
coresight_release_path(path);
--
2.17.1