[PATCH v1 06/11] coresight: Control path during CPU PM

[James Clark]

On 16/05/2025 5:07 pm, Leo Yan wrote:
> This commit extends control over CoreSight components on an activated path
> during CPU PM.
> 
> An activated path is recorded in the 'path' field of coresight_device
> structure.  The patch pointer is cleared when the path is disabled.

patch -> path

> Traverses the links on the path to disable and re-enable components during
> CPU low-power modes.
> 
> Signed-off-by: Leo Yan <leo.yan at arm.com>
> ---
>   drivers/hwtracing/coresight/coresight-core.c | 94 ++++++++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 94 insertions(+)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
> index 8f565bb3c535..075d485dcea5 100644
> --- a/drivers/hwtracing/coresight/coresight-core.c
> +++ b/drivers/hwtracing/coresight/coresight-core.c
> @@ -596,6 +596,94 @@ int coresight_enable_path(struct coresight_path *path, enum cs_mode mode,
>   	goto out;
>   }
>   
> +static int coresight_save_path(struct coresight_path *path)
 > +{> +	u32 type;
> +	struct coresight_node *nd;
> +	struct coresight_device *source, *sink;
> +
> +	if (!path)
> +		return 0;
> +
> +	source = coresight_get_source(path);
> +
> +	/*
> +	 * Do a sanity check as the source device must have been enabled when
> +	 * run at here.
> +	 */
> +	if (coresight_get_mode(source) == CS_MODE_DISABLED)
> +		return -EINVAL;
> +
> +	sink = coresight_get_sink(path);
> +
> +	/*
> +	 * Disable links. Deliberately to skip disabling the sink to avoid
> +	 * latency.
> +	 */
> +	nd = list_first_entry(&path->path_list, struct coresight_node, link);
> +	list_for_each_entry_continue(nd, &path->path_list, link) {
> +		struct coresight_device *csdev, *parent, *child;
> +
> +		csdev = nd->csdev;
> +		type = csdev->type;
> +
> +		/* Adjust type for LINKSINK */
> +		if (type == CORESIGHT_DEV_TYPE_LINKSINK)
> +			type = (csdev == sink) ? CORESIGHT_DEV_TYPE_SINK :
> +						 CORESIGHT_DEV_TYPE_LINK;
> +

Not sure if we want to disable helper devices too?

> +		if (type != CORESIGHT_DEV_TYPE_LINK)
> +			continue;
> +
> +		parent = list_prev_entry(nd, link)->csdev;
> +		child = list_next_entry(nd, link)->csdev;
> +		coresight_disable_link(csdev, parent, child, source);
> +	}
> +
> +	return 0;
> +}
> +
> +static void coresight_restore_path(struct coresight_path *path)
> +{
> +	int ret;
> +	u32 type;
> +	struct coresight_device *source, *sink;
> +	struct coresight_node *nd;
> +
> +	if (!path)
> +		return;
> +
> +	source = coresight_get_source(path);
> +	if (coresight_get_mode(source) == CS_MODE_DISABLED)
> +		return;
> +
> +	sink = coresight_get_sink(path);
> +
> +	list_for_each_entry_reverse(nd, &path->path_list, link) {
> +		struct coresight_device *csdev, *parent, *child;
> +
> +		csdev = nd->csdev;
> +		type = csdev->type;
> +
> +		if (type == CORESIGHT_DEV_TYPE_LINKSINK)
> +			type = (csdev == sink) ? CORESIGHT_DEV_TYPE_SINK :
> +						 CORESIGHT_DEV_TYPE_LINK;
> +
> +		if (type != CORESIGHT_DEV_TYPE_LINK)
> +			continue;
> +
> +		parent = list_prev_entry(nd, link)->csdev;
> +		child = list_next_entry(nd, link)->csdev;
> +		ret = coresight_enable_link(csdev, parent, child,
> +					    coresight_get_source(path));
> +		if (ret) {
> +			dev_err(&csdev->dev, "Failed to restore\n");
> +			coresight_disable_path_from(path, nd);
> +			return;
> +		}
> +	}
> +}
> +
>   struct coresight_device *coresight_get_sink(struct coresight_path *path)
>   {
>   	struct coresight_device *csdev;
> @@ -1605,9 +1693,15 @@ static int coresight_cpu_pm_notify(struct notifier_block *nb, unsigned long cmd,
>   	case CPU_PM_ENTER:
>   		if (coresight_save_source(source))
>   			return NOTIFY_BAD;
> +
> +		if (coresight_save_path(source->path)) {
> +			coresight_restore_source(source);
> +			return NOTIFY_BAD;
> +		}
>   		break;
>   	case CPU_PM_EXIT:
>   	case CPU_PM_ENTER_FAILED:
> +		coresight_restore_path(source->path);
>   		coresight_restore_source(source);
>   		break;
>   	default: