cxl/core: Split decoder setup into alloc + add

The kbuild robot reports:

    drivers/cxl/core/bus.c:516:1: warning: stack frame size (1032) exceeds
    limit (1024) in function 'devm_cxl_add_decoder'

It is also the case the devm_cxl_add_decoder() is unwieldy to use for
all the different decoder types. Fix the stack usage by splitting the
creation into alloc and add steps. This also allows for context
specific construction before adding.

With the split the caller is responsible for registering a devm callback
to trigger device_unregister() for the decoder rather than it being
implicit in the decoder registration. I.e. the routine that calls alloc
is responsible for calling put_device() if the "add" operation fails.

Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Nathan Chancellor <nathan@kernel.org>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Ben Widawsky <ben.widawsky@intel.com>
Link: https://lore.kernel.org/r/163225205828.3038145.6831131648369404859.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 60 insertions, 24 deletions

diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
index d39cc797a64e..af1c6c1875ac 100644
--- a/drivers/cxl/acpi.c
+++ b/drivers/cxl/acpi.c
@@ -82,7 +82,6 @@ static void cxl_add_cfmws_decoders(struct device *dev,
 	struct cxl_decoder *cxld;
 	acpi_size len, cur = 0;
 	void *cedt_subtable;
-	unsigned long flags;
 	int rc;
 
 	len = acpi_cedt->length - sizeof(*acpi_cedt);
@@ -119,24 +118,36 @@ static void cxl_add_cfmws_decoders(struct device *dev,
 		for (i = 0; i < CFMWS_INTERLEAVE_WAYS(cfmws); i++)
 			target_map[i] = cfmws->interleave_targets[i];
 
-		flags = cfmws_to_decoder_flags(cfmws->restrictions);
-		cxld = devm_cxl_add_decoder(dev, root_port,
-					    CFMWS_INTERLEAVE_WAYS(cfmws),
-					    cfmws->base_hpa, cfmws->window_size,
-					    CFMWS_INTERLEAVE_WAYS(cfmws),
-					    CFMWS_INTERLEAVE_GRANULARITY(cfmws),
-					    CXL_DECODER_EXPANDER,
-					    flags, target_map);
-
-		if (IS_ERR(cxld)) {
+		cxld = cxl_decoder_alloc(root_port,
+					 CFMWS_INTERLEAVE_WAYS(cfmws));
+		if (IS_ERR(cxld))
+			goto next;
+
+		cxld->flags = cfmws_to_decoder_flags(cfmws->restrictions);
+		cxld->target_type = CXL_DECODER_EXPANDER;
+		cxld->range = (struct range) {
+			.start = cfmws->base_hpa,
+			.end = cfmws->base_hpa + cfmws->window_size - 1,
+		};
+		cxld->interleave_ways = CFMWS_INTERLEAVE_WAYS(cfmws);
+		cxld->interleave_granularity =
+			CFMWS_INTERLEAVE_GRANULARITY(cfmws);
+
+		rc = cxl_decoder_add(cxld, target_map);
+		if (rc)
+			put_device(&cxld->dev);
+		else
+			rc = cxl_decoder_autoremove(dev, cxld);
+		if (rc) {
 			dev_err(dev, "Failed to add decoder for %#llx-%#llx\n",
 				cfmws->base_hpa, cfmws->base_hpa +
 				cfmws->window_size - 1);
-		} else {
-			dev_dbg(dev, "add: %s range %#llx-%#llx\n",
-				dev_name(&cxld->dev), cfmws->base_hpa,
-				 cfmws->base_hpa + cfmws->window_size - 1);
+			goto next;
 		}
+		dev_dbg(dev, "add: %s range %#llx-%#llx\n",
+			dev_name(&cxld->dev), cfmws->base_hpa,
+			cfmws->base_hpa + cfmws->window_size - 1);
+next:
 		cur += c->length;
 	}
 }
@@ -266,6 +277,7 @@ static int add_host_bridge_uport(struct device *match, void *arg)
 	struct acpi_device *bridge = to_cxl_host_bridge(host, match);
 	struct acpi_pci_root *pci_root;
 	struct cxl_walk_context ctx;
+	int single_port_map[1], rc;
 	struct cxl_decoder *cxld;
 	struct cxl_dport *dport;
 	struct cxl_port *port;
@@ -301,22 +313,46 @@ static int add_host_bridge_uport(struct device *match, void *arg)
 		return -ENODEV;
 	if (ctx.error)
 		return ctx.error;
+	if (ctx.count > 1)
+		return 0;
 
 	/* TODO: Scan CHBCR for HDM Decoder resources */
 
 	/*
-	 * In the single-port host-bridge case there are no HDM decoders
-	 * in the CHBCR and a 1:1 passthrough decode is implied.
+	 * Per the CXL specification (8.2.5.12 CXL HDM Decoder Capability
+	 * Structure) single ported host-bridges need not publish a decoder
+	 * capability when a passthrough decode can be assumed, i.e. all
+	 * transactions that the uport sees are claimed and passed to the single
+	 * dport. Disable the range until the first CXL region is enumerated /
+	 * activated.
 	 */
-	if (ctx.count == 1) {
-		cxld = devm_cxl_add_passthrough_decoder(host, port);
-		if (IS_ERR(cxld))
-			return PTR_ERR(cxld);
+	cxld = cxl_decoder_alloc(port, 1);
+	if (IS_ERR(cxld))
+		return PTR_ERR(cxld);
+
+	cxld->interleave_ways = 1;
+	cxld->interleave_granularity = PAGE_SIZE;
+	cxld->target_type = CXL_DECODER_EXPANDER;
+	cxld->range = (struct range) {
+		.start = 0,
+		.end = -1,
+	};
 
-		dev_dbg(host, "add: %s\n", dev_name(&cxld->dev));
-	}
+	device_lock(&port->dev);
+	dport = list_first_entry(&port->dports, typeof(*dport), list);
+	device_unlock(&port->dev);
 
-	return 0;
+	single_port_map[0] = dport->port_id;
+
+	rc = cxl_decoder_add(cxld, single_port_map);
+	if (rc)
+		put_device(&cxld->dev);
+	else
+		rc = cxl_decoder_autoremove(host, cxld);
+
+	if (rc == 0)
+		dev_dbg(host, "add: %s\n", dev_name(&cxld->dev));
+	return rc;
 }
 
 static int add_host_bridge_dport(struct device *match, void *arg)