Re: [PATCH v11 14/27] coresight: Move source helper disabling to coresight_disable_path()

Suzuki K Poulose
2026-05-06T09:07:10Z

On 01/05/2026 17:47, Leo Yan wrote:
> Move source helper disabling to coresight_disable_path() to pair it with
> coresight_enable_path().
>
> In coresight_enable_path(), if enabling a node fails, iterate to the
> next node (which is the last successfully enabled node) and pass it to
> coresight_disable_path() for rollback. If the failed node is the last
> node on the path, no device is actually enabled, so bail out directly.
>
> As a result, coresight_disable_source() only controls the source,
> leaving the associated helpers to be managed as part of path. Update
> the comment to reflect this change.
>
> Tested-by: Jie Gan <jie.gan@oss.qualcomm.com>
> Reviewed-by: Yeoreum Yun <yeoreum.yun@arm.com>
> Reviewed-by: James Clark <james.clark@linaro.org>
> Tested-by: James Clark <james.clark@linaro.org>
> Signed-off-by: Leo Yan <leo.yan@arm.com>
> ---
> drivers/hwtracing/coresight/coresight-core.c | 38 +++++++++++++---------------
> 1 file changed, 17 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
> index 0c11e7fff1bd5cf504b17241595d83a1d11bcf40..6ab80ae7c389e9031d4ab065d83bb676fd12160b 100644
> --- a/drivers/hwtracing/coresight/coresight-core.c
> +++ b/drivers/hwtracing/coresight/coresight-core.c
> @@ -447,19 +447,12 @@ static void coresight_disable_helpers(struct coresight_device *csdev,
> }
>
> /*
> - * Helper function to call source_ops(csdev)->disable and also disable the
> - * helpers.
> - *
> - * There is an imbalance between coresight_enable_path() and
> - * coresight_disable_path(). Enabling also enables the source's helpers as part
> - * of the path, but disabling always skips the first item in the path (which is
> - * the source), so sources and their helpers don't get disabled as part of that
> - * function and we need the extra step here.
> + * coresight_disable_source() only disables the source, but do nothing for
> + * the associated helpers, which are controlled as part of the path.
> */
> void coresight_disable_source(struct coresight_device *csdev, void *data)
> {
> source_ops(csdev)->disable(csdev, data);
> - coresight_disable_helpers(csdev, NULL);
> }
> EXPORT_SYMBOL_GPL(coresight_disable_source);
>
> @@ -486,9 +479,9 @@ int coresight_resume_source(struct coresight_device *csdev)
> EXPORT_SYMBOL_GPL(coresight_resume_source);
>
> /*
> - * coresight_disable_path_from : Disable components in the given path beyond
> - * @nd in the list. If @nd is NULL, all the components, except the SOURCE are
> - * disabled.
> + * coresight_disable_path_from : Disable components in the given path starting
> + * from @nd in the list. If @nd is NULL, all the components, except the SOURCE
> + * are disabled.
> */
> static void coresight_disable_path_from(struct coresight_path *path,
> struct coresight_node *nd)
> @@ -499,7 +492,7 @@ static void coresight_disable_path_from(struct coresight_path *path,
> if (!nd)
> nd = list_first_entry(&path->path_list, struct coresight_node, link);
>
> - list_for_each_entry_continue(nd, &path->path_list, link) {
> + list_for_each_entry_from(nd, &path->path_list, link) {
> csdev = nd->csdev;
> type = csdev->type;
>
> @@ -519,12 +512,6 @@ static void coresight_disable_path_from(struct coresight_path *path,
> coresight_disable_sink(csdev);
> break;
> case CORESIGHT_DEV_TYPE_SOURCE:
> - /*
> - * We skip the first node in the path assuming that it
> - * is the source. So we don't expect a source device in
> - * the middle of a path.
> - */
> - WARN_ON(1);
> break;
> case CORESIGHT_DEV_TYPE_LINK:
> parent = list_prev_entry(nd, link)->csdev;

--8>--

> @@ -580,12 +567,16 @@ int coresight_enable_path(struct coresight_path *path, enum cs_mode mode)
> {
> int ret = 0;
> u32 type;
> - struct coresight_node *nd;
> + struct coresight_node *nd, *last;
> struct coresight_device *csdev, *parent, *child;
> struct coresight_device *source;
>
> source = coresight_get_source(path);
> - list_for_each_entry_reverse(nd, &path->path_list, link) {
> +
> + last = list_last_entry(&path->path_list, struct coresight_node, link);
> +
> + nd = last;
> + list_for_each_entry_from_reverse(nd, &path->path_list, link) {
> csdev = nd->csdev;
> type = csdev->type;
>
> @@ -639,6 +630,11 @@ int coresight_enable_path(struct coresight_path *path, enum cs_mode mode)
> err_disable_helpers:
> coresight_disable_helpers(csdev, path);
> err_disable_path:
> + /* No device is actually enabled */
> + if (nd == last)
> + goto out;
+

This hunk seems to be different from the one described in the commit and
should be a different patch if at all we need it ?
Moreover, this looks unnecessary. We already do the check to see if we
didn't enable any device. See CORESIGHT_DEVICE_TYPE_SINK case.

Suzuki

> + nd = list_next_entry(nd, link);
> coresight_disable_path_from(path, nd);
> goto out;
> }
>