cxl/core: Generalize dport enumeration in the core

The core houses infrastructure for decoder resources. A CXL port's
dports are more closely related to decoder infrastructure than topology
enumeration. Implement generic PCI based dport enumeration in the core,
i.e. arrange for existing root port enumeration from cxl_acpi to share
code with switch port enumeration which just amounts to a small
difference in a pci_walk_bus() invocation once the appropriate 'struct
pci_bus' has been retrieved.

Set the convention that decoder objects are registered after all dports
are enumerated. This enables userspace to know when the CXL core is
finished establishing 'dportX' links underneath the 'portX' object.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/164368114191.354031.5270501846455462665.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

3 files changed, 154 insertions, 39 deletions

diff --git a/drivers/cxl/core/Makefile b/drivers/cxl/core/Makefile
index a90202ac88d2..91057f0ec763 100644
--- a/drivers/cxl/core/Makefile
+++ b/drivers/cxl/core/Makefile
@@ -7,3 +7,4 @@ cxl_core-y += pmem.o
 cxl_core-y += regs.o
 cxl_core-y += memdev.o
 cxl_core-y += mbox.o
+cxl_core-y += pci.o
diff --git a/drivers/cxl/core/pci.c b/drivers/cxl/core/pci.c
new file mode 100644
index 000000000000..c5a9e03ed477
--- /dev/null
+++ b/drivers/cxl/core/pci.c
@@ -0,0 +1,101 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright(c) 2021 Intel Corporation. All rights reserved. */
+#include <linux/device.h>
+#include <linux/pci.h>
+#include <cxlpci.h>
+#include <cxl.h>
+#include "core.h"
+
+/**
+ * DOC: cxl core pci
+ *
+ * Compute Express Link protocols are layered on top of PCIe. CXL core provides
+ * a set of helpers for CXL interactions which occur via PCIe.
+ */
+
+struct cxl_walk_context {
+	struct pci_bus *bus;
+	struct device *host;
+	struct cxl_port *port;
+	int type;
+	int error;
+	int count;
+};
+
+static int match_add_dports(struct pci_dev *pdev, void *data)
+{
+	struct cxl_walk_context *ctx = data;
+	struct cxl_port *port = ctx->port;
+	int type = pci_pcie_type(pdev);
+	struct cxl_register_map map;
+	struct cxl_dport *dport;
+	u32 lnkcap, port_num;
+	int rc;
+
+	if (pdev->bus != ctx->bus)
+		return 0;
+	if (!pci_is_pcie(pdev))
+		return 0;
+	if (type != ctx->type)
+		return 0;
+	if (pci_read_config_dword(pdev, pci_pcie_cap(pdev) + PCI_EXP_LNKCAP,
+				  &lnkcap))
+		return 0;
+
+	rc = cxl_find_regblock(pdev, CXL_REGLOC_RBI_COMPONENT, &map);
+	if (rc)
+		dev_dbg(&port->dev, "failed to find component registers\n");
+
+	port_num = FIELD_GET(PCI_EXP_LNKCAP_PN, lnkcap);
+	cxl_device_lock(&port->dev);
+	dport = devm_cxl_add_dport(ctx->host, port, &pdev->dev, port_num,
+				   cxl_regmap_to_base(pdev, &map));
+	cxl_device_unlock(&port->dev);
+	if (IS_ERR(dport)) {
+		ctx->error = PTR_ERR(dport);
+		return PTR_ERR(dport);
+	}
+	ctx->count++;
+
+	dev_dbg(&port->dev, "add dport%d: %s\n", port_num, dev_name(&pdev->dev));
+
+	return 0;
+}
+
+/**
+ * devm_cxl_port_enumerate_dports - enumerate downstream ports of the upstream port
+ * @host: devm context
+ * @port: cxl_port whose ->uport is the upstream of dports to be enumerated
+ *
+ * Returns a positive number of dports enumerated or a negative error
+ * code.
+ */
+int devm_cxl_port_enumerate_dports(struct device *host, struct cxl_port *port)
+{
+	struct pci_bus *bus = cxl_port_to_pci_bus(port);
+	struct cxl_walk_context ctx;
+	int type;
+
+	if (!bus)
+		return -ENXIO;
+
+	if (pci_is_root_bus(bus))
+		type = PCI_EXP_TYPE_ROOT_PORT;
+	else
+		type = PCI_EXP_TYPE_DOWNSTREAM;
+
+	ctx = (struct cxl_walk_context) {
+		.host = host,
+		.port = port,
+		.bus = bus,
+		.type = type,
+	};
+	pci_walk_bus(bus, match_add_dports, &ctx);
+
+	if (ctx.count == 0)
+		return -ENODEV;
+	if (ctx.error)
+		return ctx.error;
+	return ctx.count;
+}
+EXPORT_SYMBOL_NS_GPL(devm_cxl_port_enumerate_dports, CXL);
diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
index 369cc52e0837..fee9c7affef4 100644
--- a/drivers/cxl/core/port.c
+++ b/drivers/cxl/core/port.c
@@ -243,22 +243,10 @@ struct cxl_decoder *to_cxl_decoder(struct device *dev)
 }
 EXPORT_SYMBOL_NS_GPL(to_cxl_decoder, CXL);
 
-static void cxl_dport_release(struct cxl_dport *dport)
-{
-	list_del(&dport->list);
-	put_device(dport->dport);
-	kfree(dport);
-}
-
 static void cxl_port_release(struct device *dev)
 {
 	struct cxl_port *port = to_cxl_port(dev);
-	struct cxl_dport *dport, *_d;
 
-	cxl_device_lock(dev);
-	list_for_each_entry_safe(dport, _d, &port->dports, list)
-		cxl_dport_release(dport);
-	cxl_device_unlock(dev);
 	ida_free(&cxl_port_ida, port->id);
 	kfree(port);
 }
@@ -292,18 +280,7 @@ EXPORT_SYMBOL_NS_GPL(to_cxl_port, CXL);
 static void unregister_port(void *_port)
 {
 	struct cxl_port *port = _port;
-	struct cxl_dport *dport;
 
-	cxl_device_lock(&port->dev);
-	list_for_each_entry(dport, &port->dports, list) {
-		char link_name[CXL_TARGET_STRLEN];
-
-		if (snprintf(link_name, CXL_TARGET_STRLEN, "dport%d",
-			     dport->port_id) >= CXL_TARGET_STRLEN)
-			continue;
-		sysfs_remove_link(&port->dev.kobj, link_name);
-	}
-	cxl_device_unlock(&port->dev);
 	device_unregister(&port->dev);
 }
 
@@ -532,51 +509,87 @@ static int add_dport(struct cxl_port *port, struct cxl_dport *new)
 	return dup ? -EEXIST : 0;
 }
 
+static void cxl_dport_remove(void *data)
+{
+	struct cxl_dport *dport = data;
+	struct cxl_port *port = dport->port;
+
+	put_device(dport->dport);
+	cxl_device_lock(&port->dev);
+	list_del(&dport->list);
+	cxl_device_unlock(&port->dev);
+}
+
+static void cxl_dport_unlink(void *data)
+{
+	struct cxl_dport *dport = data;
+	struct cxl_port *port = dport->port;
+	char link_name[CXL_TARGET_STRLEN];
+
+	sprintf(link_name, "dport%d", dport->port_id);
+	sysfs_remove_link(&port->dev.kobj, link_name);
+}
+
 /**
- * cxl_add_dport - append downstream port data to a cxl_port
+ * devm_cxl_add_dport - append downstream port data to a cxl_port
+ * @host: devm context for allocations
  * @port: the cxl_port that references this dport
  * @dport_dev: firmware or PCI device representing the dport
  * @port_id: identifier for this dport in a decoder's target list
  * @component_reg_phys: optional location of CXL component registers
  *
- * Note that all allocations and links are undone by cxl_port deletion
- * and release.
+ * Note that dports are appended to the devm release action's of the
+ * either the port's host (for root ports), or the port itself (for
+ * switch ports)
  */
-int cxl_add_dport(struct cxl_port *port, struct device *dport_dev, int port_id,
-		  resource_size_t component_reg_phys)
+struct cxl_dport *devm_cxl_add_dport(struct device *host, struct cxl_port *port,
+				     struct device *dport_dev, int port_id,
+				     resource_size_t component_reg_phys)
 {
 	char link_name[CXL_TARGET_STRLEN];
 	struct cxl_dport *dport;
 	int rc;
 
+	if (!host->driver) {
+		dev_WARN_ONCE(&port->dev, 1, "dport:%s bad devm context\n",
+			      dev_name(dport_dev));
+		return ERR_PTR(-ENXIO);
+	}
+
 	if (snprintf(link_name, CXL_TARGET_STRLEN, "dport%d", port_id) >=
 	    CXL_TARGET_STRLEN)
-		return -EINVAL;
+		return ERR_PTR(-EINVAL);
 
-	dport = kzalloc(sizeof(*dport), GFP_KERNEL);
+	dport = devm_kzalloc(host, sizeof(*dport), GFP_KERNEL);
 	if (!dport)
-		return -ENOMEM;
+		return ERR_PTR(-ENOMEM);
 
 	INIT_LIST_HEAD(&dport->list);
-	dport->dport = get_device(dport_dev);
+	dport->dport = dport_dev;
 	dport->port_id = port_id;
 	dport->component_reg_phys = component_reg_phys;
 	dport->port = port;
 
 	rc = add_dport(port, dport);
 	if (rc)
-		goto err;
+		return ERR_PTR(rc);
+
+	get_device(dport_dev);
+	rc = devm_add_action_or_reset(host, cxl_dport_remove, dport);
+	if (rc)
+		return ERR_PTR(rc);
 
 	rc = sysfs_create_link(&port->dev.kobj, &dport_dev->kobj, link_name);
 	if (rc)
-		goto err;
+		return ERR_PTR(rc);
 
-	return 0;
-err:
-	cxl_dport_release(dport);
-	return rc;
+	rc = devm_add_action_or_reset(host, cxl_dport_unlink, dport);
+	if (rc)
+		return ERR_PTR(rc);
+
+	return dport;
 }
-EXPORT_SYMBOL_NS_GPL(cxl_add_dport, CXL);
+EXPORT_SYMBOL_NS_GPL(devm_cxl_add_dport, CXL);
 
 static int decoder_populate_targets(struct cxl_decoder *cxld,
 				    struct cxl_port *port, int *target_map)