[PATCH v4 08/14] cxl/region: Factor out code to find the root decoder

[Robert Richter <rrichter@amd.com>]

In function cxl_add_to_region() there is code to determine the root
decoder associated to an endpoint decoder. Factor out that code for
later reuse. This has the benefit of reducing cxl_add_to_region()'s
function complexity.

The reference of cxlrd_dev can be freed earlier. Since the root
decoder exists as long as the root port exists and the endpoint
already holds a reference to the root port, this additional reference
is not needed. Though it looks obvious to use __free() for the
reference of cxlrd_dev here too, this is done in a later rework. So
just move the code.

Signed-off-by: Robert Richter <rrichter@amd.com>
Reviewed-by: Gregory Price <gourry@gourry.net>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Tested-by: Gregory Price <gourry@gourry.net>
---
 drivers/cxl/core/region.c | 55 ++++++++++++++++++++++++++-------------
 1 file changed, 37 insertions(+), 18 deletions(-)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 8244a27d0fd6..7d9d9b8f9eea 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -3212,6 +3212,38 @@ static int match_root_decoder_by_range(struct device *dev,
 	return range_contains(r1, r2);
 }
 
+static struct cxl_root_decoder *
+cxl_find_root_decoder(struct cxl_endpoint_decoder *cxled)
+{
+	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
+	struct cxl_port *port = cxled_to_port(cxled);
+	struct cxl_root *cxl_root __free(put_cxl_root) = find_cxl_root(port);
+	struct cxl_decoder *cxld = &cxled->cxld;
+	struct range *hpa = &cxld->hpa_range;
+	struct device *cxlrd_dev;
+
+	cxlrd_dev = device_find_child(&cxl_root->port.dev, hpa,
+				      match_root_decoder_by_range);
+	if (!cxlrd_dev) {
+		dev_err(cxlmd->dev.parent,
+			"%s:%s no CXL window for range %#llx:%#llx\n",
+			dev_name(&cxlmd->dev), dev_name(&cxld->dev),
+			cxld->hpa_range.start, cxld->hpa_range.end);
+		return NULL;
+	}
+
+	/*
+	 * device_find_child() created a reference to the root
+	 * decoder. Since the root decoder exists as long as the root
+	 * port exists and the endpoint already holds a reference to
+	 * the root port, this additional reference is not needed.
+	 * Free it here.
+	 */
+	put_device(cxlrd_dev);
+
+	return to_cxl_root_decoder(cxlrd_dev);
+}
+
 static int match_region_by_range(struct device *dev, const void *data)
 {
 	struct cxl_region_params *p;
@@ -3386,29 +3418,17 @@ static struct cxl_region *construct_region(struct cxl_root_decoder *cxlrd,
 
 int cxl_add_to_region(struct cxl_endpoint_decoder *cxled)
 {
-	struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
-	struct cxl_port *port = cxled_to_port(cxled);
-	struct cxl_root *cxl_root __free(put_cxl_root) = find_cxl_root(port);
 	struct range *hpa = &cxled->cxld.hpa_range;
-	struct cxl_decoder *cxld = &cxled->cxld;
-	struct device *cxlrd_dev, *region_dev;
+	struct device *region_dev;
 	struct cxl_root_decoder *cxlrd;
 	struct cxl_region_params *p;
 	struct cxl_region *cxlr;
 	bool attach = false;
 	int rc;
 
-	cxlrd_dev = device_find_child(&cxl_root->port.dev, &cxld->hpa_range,
-				      match_root_decoder_by_range);
-	if (!cxlrd_dev) {
-		dev_err(cxlmd->dev.parent,
-			"%s:%s no CXL window for range %#llx:%#llx\n",
-			dev_name(&cxlmd->dev), dev_name(&cxld->dev),
-			cxld->hpa_range.start, cxld->hpa_range.end);
+	cxlrd = cxl_find_root_decoder(cxled);
+	if (!cxlrd)
 		return -ENXIO;
-	}
-
-	cxlrd = to_cxl_root_decoder(cxlrd_dev);
 
 	/*
 	 * Ensure that if multiple threads race to construct_region() for @hpa
@@ -3426,7 +3446,7 @@ int cxl_add_to_region(struct cxl_endpoint_decoder *cxled)
 
 	rc = PTR_ERR_OR_ZERO(cxlr);
 	if (rc)
-		goto out;
+		return rc;
 
 	attach_target(cxlr, cxled, -1, TASK_UNINTERRUPTIBLE);
 
@@ -3447,8 +3467,7 @@ int cxl_add_to_region(struct cxl_endpoint_decoder *cxled)
 	}
 
 	put_device(region_dev);
-out:
-	put_device(cxlrd_dev);
+
 	return rc;
 }
 EXPORT_SYMBOL_NS_GPL(cxl_add_to_region, "CXL");
-- 
2.39.5