cxl/region: Add a dev_err() on missing target list entries

Broken target lists are hard to discover as the driver fails at a
later initialization stage. Add an error message for this.

Example log messages:

  cxl_mem mem1: failed to find endpoint6:0000:e0:01.3 in target list of decoder1.1
  cxl_port endpoint6: failed to register decoder6.0: -6
  cxl_port endpoint6: probe: 0

Signed-off-by: Robert Richter <[email protected]>
Reviewed-by: Gregory Price <[email protected]>
Reviewed-by: Jonathan Cameron <[email protected]>
Reviewed-by: Dave Jiang <[email protected]>
Reviewed-by: Dan Williams <[email protected]>
Reviewed-by: Alison Schofield <[email protected]>
Reviewed-by: "Fabio M. De Francesco" <[email protected]>
Tested-by: Gregory Price <[email protected]>
Acked-by: Dan Williams <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Dave Jiang <[email protected]>

Author: Robert Richter

drivers/cxl/core/region.c

@@ -1809,6 +1809,13 @@ static int find_pos_and_ways(struct cxl_port *port, struct range *range,
 	}
 	put_device(dev);
 
+	if (rc)
+		dev_err(port->uport_dev,
+			"failed to find %s:%s in target list of %s\n",
+			dev_name(&port->dev),
+			dev_name(port->parent_dport->dport_dev),
+			dev_name(&cxlsd->cxld.dev));
+
 	return rc;
 }