linux-kernel - [PATCH v2] interconnect: Add helpers for enabling/disabling a path

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Message-Id: <20200507120846.8354-1-georgi.djakov@linaro.org>
Date:   Thu,  7 May 2020 15:08:46 +0300
From:   Georgi Djakov <georgi.djakov@...aro.org>
To:     linux-pm@...r.kernel.org
Cc:     evgreen@...omium.org, bjorn.andersson@...aro.org, mka@...omium.org,
        akashast@...eaurora.org, linux-kernel@...r.kernel.org,
        georgi.djakov@...aro.org
Subject: [PATCH v2] interconnect: Add helpers for enabling/disabling a path

There is a repeated pattern in multiple drivers where they want to switch
the bandwidth between zero and some other value. This is happening often
in the suspend/resume callbacks. Let's add helper functions to enable and
disable the path, so that callers don't have to take care of remembering
the bandwidth values and handle this in the framework instead.

With this patch the users can call icc_disable() and icc_enable() to lower
their bandwidth request to zero and then restore it back to it's previous
value.

Suggested-by: Evan Green <evgreen@...omium.org>
Suggested-by: Bjorn Andersson <bjorn.andersson@...aro.org>
Signed-off-by: Georgi Djakov <georgi.djakov@...aro.org>
---
v2: https://lore.kernel.org/r/20200428091650.27669-1-georgi.djakov@linaro.org/
* Extract the common code into __icc_enable() (Matthias)


 drivers/interconnect/core.c     | 39 ++++++++++++++++++++++++++++++++-
 drivers/interconnect/internal.h |  2 ++
 include/linux/interconnect.h    | 12 ++++++++++
 3 files changed, 52 insertions(+), 1 deletion(-)

diff --git a/drivers/interconnect/core.c b/drivers/interconnect/core.c
index f5699ed34e43..d5e0f93c942d 100644
--- a/drivers/interconnect/core.c
+++ b/drivers/interconnect/core.c
@@ -158,6 +158,7 @@ static struct icc_path *path_init(struct device *dev, struct icc_node *dst,
 		hlist_add_head(&path->reqs[i].req_node, &node->req_list);
 		path->reqs[i].node = node;
 		path->reqs[i].dev = dev;
+		path->reqs[i].enabled = true;
 		/* reference to previous node was saved during path traversal */
 		node = node->reverse;
 	}
@@ -249,9 +250,12 @@ static int aggregate_requests(struct icc_node *node)
 	if (p->pre_aggregate)
 		p->pre_aggregate(node);
 
-	hlist_for_each_entry(r, &node->req_list, req_node)
+	hlist_for_each_entry(r, &node->req_list, req_node) {
+		if (!r->enabled)
+			continue;
 		p->aggregate(node, r->tag, r->avg_bw, r->peak_bw,
 			     &node->avg_bw, &node->peak_bw);
+	}
 
 	return 0;
 }
@@ -571,6 +575,39 @@ int icc_set_bw(struct icc_path *path, u32 avg_bw, u32 peak_bw)
 }
 EXPORT_SYMBOL_GPL(icc_set_bw);
 
+static int __icc_enable(struct icc_path *path, bool enable)
+{
+	int i;
+
+	if (!path)
+		return 0;
+
+	if (WARN_ON(IS_ERR(path) || !path->num_nodes))
+		return -EINVAL;
+
+	mutex_lock(&icc_lock);
+
+	for (i = 0; i < path->num_nodes; i++)
+		path->reqs[i].enabled = enable;
+
+	mutex_unlock(&icc_lock);
+
+	return icc_set_bw(path, path->reqs[0].avg_bw,
+			  path->reqs[0].peak_bw);
+}
+
+int icc_disable(struct icc_path *path)
+{
+	return __icc_enable(path, false);
+}
+EXPORT_SYMBOL_GPL(icc_disable);
+
+int icc_enable(struct icc_path *path)
+{
+	return __icc_enable(path, true);
+}
+EXPORT_SYMBOL_GPL(icc_enable);
+
 /**
  * icc_get() - return a handle for path between two endpoints
  * @dev: the device requesting the path
diff --git a/drivers/interconnect/internal.h b/drivers/interconnect/internal.h
index bf18cb7239df..f5f82a5c939e 100644
--- a/drivers/interconnect/internal.h
+++ b/drivers/interconnect/internal.h
@@ -14,6 +14,7 @@
  * @req_node: entry in list of requests for the particular @node
  * @node: the interconnect node to which this constraint applies
  * @dev: reference to the device that sets the constraints
+ * @enabled: indicates whether the path with this request is enabled
  * @tag: path tag (optional)
  * @avg_bw: an integer describing the average bandwidth in kBps
  * @peak_bw: an integer describing the peak bandwidth in kBps
@@ -22,6 +23,7 @@ struct icc_req {
 	struct hlist_node req_node;
 	struct icc_node *node;
 	struct device *dev;
+	bool enabled;
 	u32 tag;
 	u32 avg_bw;
 	u32 peak_bw;
diff --git a/include/linux/interconnect.h b/include/linux/interconnect.h
index 770692421f4c..2b7b331c9354 100644
--- a/include/linux/interconnect.h
+++ b/include/linux/interconnect.h
@@ -30,6 +30,8 @@ struct icc_path *icc_get(struct device *dev, const int src_id,
 struct icc_path *of_icc_get(struct device *dev, const char *name);
 struct icc_path *devm_of_icc_get(struct device *dev, const char *name);
 void icc_put(struct icc_path *path);
+int icc_disable(struct icc_path *path);
+int icc_enable(struct icc_path *path);
 int icc_set_bw(struct icc_path *path, u32 avg_bw, u32 peak_bw);
 void icc_set_tag(struct icc_path *path, u32 tag);
 
@@ -57,6 +59,16 @@ static inline void icc_put(struct icc_path *path)
 {
 }
 
+static inline int icc_disable(struct icc_path *path)
+{
+	return 0;
+}
+
+static inline int icc_enable(struct icc_path *path)
+{
+	return 0;
+}
+
 static inline int icc_set_bw(struct icc_path *path, u32 avg_bw, u32 peak_bw)
 {
 	return 0;