Re: [PATCH v10 1/7] interconnect: Add generic on-chip interconnect API

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Hi Joe,

On 11/27/18 20:35, Joe Perches wrote:
On Tue, 2018-11-27 at 20:03 +0200, Georgi Djakov wrote:
This patch introduces a new API to get requirements and configure the
interconnect buses across the entire chipset to fit with the current
demand.

trivial notes:

diff --git a/drivers/interconnect/core.c b/drivers/interconnect/core.c
[]
+static int apply_constraints(struct icc_path *path)
+{
+	struct icc_node *next, *prev = NULL;
+	int ret = -EINVAL;
+	int i;
+
+	for (i = 0; i < path->num_nodes; i++, prev = next) {
+		struct icc_provider *p;
+
+		next = path->reqs[i].node;
+		/*
+		 * Both endpoints should be valid master-slave pairs of the
+		 * same interconnect provider that will be configured.
+		 */
+		if (!prev || next->provider != prev->provider)
+			continue;
+
+		p = next->provider;
+
+		/* set the constraints */
+		ret = p->set(prev, next);
+		if (ret)
+			goto out;
+	}
+out:
+	return ret;
+}

The use of ", prev = next" appears somewhat tricky code.
Perhaps move the assignment of prev to the bottom of the loop.
Perhaps the temporary p assignment isn't useful either.

+int icc_set(struct icc_path *path, u32 avg_bw, u32 peak_bw)
+{
[]
+	ret = apply_constraints(path);
+	if (ret)
+		pr_debug("interconnect: error applying constraints (%d)", ret);

Ideally all pr_<foo> formats should end in '\n'

+static struct icc_node *icc_node_create_nolock(int id)
+{
+	struct icc_node *node;
+
+	/* check if node already exists */
+	node = node_find(id);
+	if (node)
+		goto out;
+
+	node = kzalloc(sizeof(*node), GFP_KERNEL);
+	if (!node) {
+		node = ERR_PTR(-ENOMEM);
+		goto out;

Generally, this code appears to overly rely on goto when
direct returns could be more readable.

+	}
+
+	id = idr_alloc(&icc_idr, node, id, id + 1, GFP_KERNEL);
+	if (WARN(id < 0, "couldn't get idr")) {

This seems to unnecessarily hide the id < 0 test in a WARN

Why is this a WARN and not a simpler
	if (id < 0) {
		[ pr_err(...); or WARN(1, ...); ]

+		kfree(node);
+		node = ERR_PTR(id);
+		goto out;
+	}
+
+	node->id = id;
+
+out:
+	return node;
+}

Thank you for helping to improve the code. The above suggestions make it cleaner indeed.

[]
diff --git a/include/linux/interconnect.h b/include/linux/interconnect.h
[]
+/* macros for converting to icc units */
+#define bps_to_icc(x)	(1)
+#define kBps_to_icc(x)	(x)
[]
+#define MBps_to_icc(x)	(x * 1000)
+#define GBps_to_icc(x)	(x * 1000 * 1000)
+#define kbps_to_icc(x)	(x / 8 + ((x) % 8 ? 1 : 0))
+#define Mbps_to_icc(x)	(x * 1000 / 8 )
+#define Gbps_to_icc(x)	(x * 1000 * 1000 / 8)

The last 5 macros should parenthesize x

Oops.. obviously i forgot to run checkpatch --strict. Will fix!

BR,
Georgi



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