cxl/core: Define a 'struct cxl_switch_decoder'

Currently 'struct cxl_decoder' contains the superset of attributes
needed for all decoder types. Before more type-specific attributes are
added to the common definition, reorganize 'struct cxl_decoder' into type
specific objects.

This patch, the first of three, factors out a cxl_switch_decoder type.
See the new kdoc for what a 'struct cxl_switch_decoder' represents in a
CXL topology.
Co-developed-by: Ben Widawsky <bwidawsk@kernel.org>
Signed-off-by: Ben Widawsky <bwidawsk@kernel.org>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/r/165784325340.1758207.5064717153608954960.stgit@dwillia2-xfh.jf.intel.comSigned-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/cxl/acpi.c

@@ -81,6 +81,7 @@ static int cxl_parse_cfmws(union acpi_subtable_headers *header, void *arg,
 	int target_map[CXL_DECODER_MAX_INTERLEAVE];
 	struct cxl_cfmws_context *ctx = arg;
 	struct cxl_port *root_port = ctx->root_port;
+	struct cxl_switch_decoder *cxlsd;
 	struct device *dev = ctx->dev;
 	struct acpi_cedt_cfmws *cfmws;
 	struct cxl_decoder *cxld;
@@ -106,10 +107,11 @@ static int cxl_parse_cfmws(union acpi_subtable_headers *header, void *arg,
 	for (i = 0; i < ways; i++)
 		target_map[i] = cfmws->interleave_targets[i];
 
-	cxld = cxl_root_decoder_alloc(root_port, ways);
+	cxlsd = cxl_root_decoder_alloc(root_port, ways);
 	if (IS_ERR(cxld))
 		return 0;
 
+	cxld = &cxlsd->cxld;
 	cxld->flags = cfmws_to_decoder_flags(cfmws->restrictions);
 	cxld->target_type = CXL_DECODER_EXPANDER;
 	cxld->hpa_range = (struct range) {

drivers/cxl/core/hdm.c

@@ -49,20 +49,20 @@ static int add_hdm_decoder(struct cxl_port *port, struct cxl_decoder *cxld,
  */
 int devm_cxl_add_passthrough_decoder(struct cxl_port *port)
 {
-	struct cxl_decoder *cxld;
+	struct cxl_switch_decoder *cxlsd;
 	struct cxl_dport *dport;
 	int single_port_map[1];
 
-	cxld = cxl_switch_decoder_alloc(port, 1);
-	if (IS_ERR(cxld))
-		return PTR_ERR(cxld);
+	cxlsd = cxl_switch_decoder_alloc(port, 1);
+	if (IS_ERR(cxlsd))
+		return PTR_ERR(cxlsd);
 
 	device_lock_assert(&port->dev);
 
 	dport = list_first_entry(&port->dports, typeof(*dport), list);
 	single_port_map[0] = dport->port_id;
 
-	return add_hdm_decoder(port, cxld, single_port_map);
+	return add_hdm_decoder(port, &cxlsd->cxld, single_port_map);
 }
 EXPORT_SYMBOL_NS_GPL(devm_cxl_add_passthrough_decoder, CXL);
 
@@ -255,14 +255,23 @@ int devm_cxl_enumerate_decoders(struct cxl_hdm *cxlhdm)
 		int rc, target_count = cxlhdm->target_count;
 		struct cxl_decoder *cxld;
 
-		if (is_cxl_endpoint(port))
+		if (is_cxl_endpoint(port)) {
 			cxld = cxl_endpoint_decoder_alloc(port);
-		else
-			cxld = cxl_switch_decoder_alloc(port, target_count);
-		if (IS_ERR(cxld)) {
-			dev_warn(&port->dev,
-				 "Failed to allocate the decoder\n");
-			return PTR_ERR(cxld);
+			if (IS_ERR(cxld)) {
+				dev_warn(&port->dev,
+					 "Failed to allocate the decoder\n");
+				return PTR_ERR(cxld);
+			}
+		} else {
+			struct cxl_switch_decoder *cxlsd;
+
+			cxlsd = cxl_switch_decoder_alloc(port, target_count);
+			if (IS_ERR(cxlsd)) {
+				dev_warn(&port->dev,
+					 "Failed to allocate the decoder\n");
+				return PTR_ERR(cxlsd);
+			}
+			cxld = &cxlsd->cxld;
 		}
 
 		rc = init_hdm_decoder(port, cxld, target_map, hdm, i);

drivers/cxl/cxl.h

@@ -220,7 +220,7 @@ enum cxl_decoder_type {
 #define CXL_DECODER_MAX_INTERLEAVE 16
 
 /**
- * struct cxl_decoder - CXL address range decode configuration
+ * struct cxl_decoder - Common CXL HDM Decoder Attributes
  * @dev: this decoder's device
  * @id: kernel device name id
  * @hpa_range: Host physical address range mapped by this decoder
@@ -228,9 +228,6 @@ enum cxl_decoder_type {
  * @interleave_granularity: data stride per dport
  * @target_type: accelerator vs expander (type2 vs type3) selector
  * @flags: memory type capabilities and locking
- * @target_lock: coordinate coherent reads of the target list
- * @nr_targets: number of elements in @target
- * @target: active ordered target list in current decoder configuration
  */
 struct cxl_decoder {
 	struct device dev;
@@ -240,6 +237,23 @@ struct cxl_decoder {
 	int interleave_granularity;
 	enum cxl_decoder_type target_type;
 	unsigned long flags;
+};
+
+/**
+ * struct cxl_switch_decoder - Switch specific CXL HDM Decoder
+ * @cxld: base cxl_decoder object
+ * @target_lock: coordinate coherent reads of the target list
+ * @nr_targets: number of elements in @target
+ * @target: active ordered target list in current decoder configuration
+ *
+ * The 'switch' decoder type represents the decoder instances of cxl_port's that
+ * route from the root of a CXL memory decode topology to the endpoints. They
+ * come in two flavors, root-level decoders, statically defined by platform
+ * firmware, and mid-level decoders, where interleave-granularity,
+ * interleave-width, and the target list are mutable.
+ */
+struct cxl_switch_decoder {
+	struct cxl_decoder cxld;
 	seqlock_t target_lock;
 	int nr_targets;
 	struct cxl_dport *target[];
@@ -371,10 +385,10 @@ struct cxl_dport *cxl_find_dport_by_dev(struct cxl_port *port,
 struct cxl_decoder *to_cxl_decoder(struct device *dev);
 bool is_root_decoder(struct device *dev);
 bool is_endpoint_decoder(struct device *dev);
-struct cxl_decoder *cxl_root_decoder_alloc(struct cxl_port *port,
-					   unsigned int nr_targets);
-struct cxl_decoder *cxl_switch_decoder_alloc(struct cxl_port *port,
-					     unsigned int nr_targets);
+struct cxl_switch_decoder *cxl_root_decoder_alloc(struct cxl_port *port,
+						  unsigned int nr_targets);
+struct cxl_switch_decoder *cxl_switch_decoder_alloc(struct cxl_port *port,
+						    unsigned int nr_targets);
 int cxl_decoder_add(struct cxl_decoder *cxld, int *target_map);
 struct cxl_decoder *cxl_endpoint_decoder_alloc(struct cxl_port *port);
 int cxl_decoder_add_locked(struct cxl_decoder *cxld, int *target_map);

tools/testing/cxl/test/cxl.c

@@ -451,14 +451,23 @@ static int mock_cxl_enumerate_decoders(struct cxl_hdm *cxlhdm)
 		struct cxl_decoder *cxld;
 		int rc;
 
-		if (target_count)
-			cxld = cxl_switch_decoder_alloc(port, target_count);
-		else
+		if (target_count) {
+			struct cxl_switch_decoder *cxlsd;
+
+			cxlsd = cxl_switch_decoder_alloc(port, target_count);
+			if (IS_ERR(cxlsd)) {
+				dev_warn(&port->dev,
+					 "Failed to allocate the decoder\n");
+				return PTR_ERR(cxlsd);
+			}
+			cxld = &cxlsd->cxld;
+		} else {
 			cxld = cxl_endpoint_decoder_alloc(port);
-		if (IS_ERR(cxld)) {
-			dev_warn(&port->dev,
-				 "Failed to allocate the decoder\n");
-			return PTR_ERR(cxld);
+			if (IS_ERR(cxld)) {
+				dev_warn(&port->dev,
+					 "Failed to allocate the decoder\n");
+				return PTR_ERR(cxld);
+			}
 		}
 
 		cxld->hpa_range = (struct range) {