linux-kernel - [PATCH v2 03/15] cxl/region: Factor out code for interleaving calculations

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Message-ID: <20250218132356.1809075-4-rrichter@amd.com>
Date: Tue, 18 Feb 2025 14:23:44 +0100
From: Robert Richter <rrichter@....com>
To: Alison Schofield <alison.schofield@...el.com>, Vishal Verma
	<vishal.l.verma@...el.com>, Ira Weiny <ira.weiny@...el.com>, Dan Williams
	<dan.j.williams@...el.com>, Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	Dave Jiang <dave.jiang@...el.com>, Davidlohr Bueso <dave@...olabs.net>
CC: <linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>, Gregory Price
	<gourry@...rry.net>, "Fabio M. De Francesco"
	<fabio.m.de.francesco@...ux.intel.com>, Terry Bowman <terry.bowman@....com>,
	Robert Richter <rrichter@....com>
Subject: [PATCH v2 03/15] cxl/region: Factor out code for interleaving calculations

Function cxl_calc_interleave_pos() contains code to calculate the
interleaving parameters of a port. Factor out that code for later
reuse. Add function cxl_port_calc_interleave() for this and introduce
struct cxl_interleave_context to collect all interleaving data.

Signed-off-by: Robert Richter <rrichter@....com>
---
 drivers/cxl/core/region.c | 63 ++++++++++++++++++++++++++-------------
 1 file changed, 43 insertions(+), 20 deletions(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index c118bda93e86..ad4a6ce37216 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -1800,27 +1800,34 @@ static int find_pos_and_ways(struct cxl_port *port, struct range *range,
 	return rc;
 }
 
+struct cxl_interleave_context {
+	struct range *hpa_range;
+	int pos;
+};
+
 /**
- * cxl_calc_interleave_pos() - calculate an endpoint position in a region
- * @cxled: endpoint decoder member of given region
+ * cxl_port_calc_interleave() - calculate interleave config of an endpoint for @port
+ * @port: Port the new position is calculated for.
+ * @ctx: Interleave context
  *
- * The endpoint position is calculated by traversing the topology from
- * the endpoint to the root decoder and iteratively applying this
- * calculation:
+ * The endpoint position for the next port is calculated by applying
+ * this calculation:
  *
  *    position = position * parent_ways + parent_pos;
  *
  * ...where @position is inferred from switch and root decoder target lists.
  *
+ * The endpoint's position in a region can be calculated by traversing
+ * the topology from the endpoint to the root decoder and iteratively
+ * applying the function for each port.
+ *
  * Return: position >= 0 on success
  *	   -ENXIO on failure
  */
-static int cxl_calc_interleave_pos(struct cxl_endpoint_decoder *cxled)
+static int cxl_port_calc_interleave(struct cxl_port *port,
+				    struct cxl_interleave_context *ctx)
 {
-	struct cxl_port *iter, *port = cxled_to_port(cxled);
-	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
-	struct range *range = &cxled->cxld.hpa_range;
-	int parent_ways = 0, parent_pos = 0, pos = 0;
+	int parent_ways = 0, parent_pos = 0;
 	int rc;
 
 	/*
@@ -1852,22 +1859,38 @@ static int cxl_calc_interleave_pos(struct cxl_endpoint_decoder *cxled)
 	 * complex topologies, including those with switches.
 	 */
 
-	/* Iterate from endpoint to root_port refining the position */
-	for (iter = port; iter; iter = parent_port_of(iter)) {
-		if (is_cxl_root(iter))
-			break;
+	if (is_cxl_root(port))
+		return 0;
 
-		rc = find_pos_and_ways(iter, range, &parent_pos, &parent_ways);
-		if (rc)
-			return rc;
+	rc = find_pos_and_ways(port, ctx->hpa_range, &parent_pos, &parent_ways);
+	if (rc)
+		return rc;
 
-		pos = pos * parent_ways + parent_pos;
-	}
+	ctx->pos = ctx->pos * parent_ways + parent_pos;
+
+	return ctx->pos;
+}
+
+static int cxl_calc_interleave_pos(struct cxl_endpoint_decoder *cxled)
+{
+	struct cxl_port *iter, *port = cxled_to_port(cxled);
+	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
+	struct cxl_interleave_context ctx;
+	int pos = 0;
+
+	ctx = (struct cxl_interleave_context) {
+		.hpa_range = &cxled->cxld.hpa_range,
+	};
+
+	for (iter = cxled_to_port(cxled); pos >= 0 && iter;
+	     iter = parent_port_of(iter))
+		pos = cxl_port_calc_interleave(iter, &ctx);
 
 	dev_dbg(&cxlmd->dev,
 		"decoder:%s parent:%s port:%s range:%#llx-%#llx pos:%d\n",
 		dev_name(&cxled->cxld.dev), dev_name(cxlmd->dev.parent),
-		dev_name(&port->dev), range->start, range->end, pos);
+		dev_name(&port->dev), ctx.hpa_range->start, ctx.hpa_range->end,
+		ctx.pos);
 
 	return pos;
 }
-- 
2.39.5