[PATCH v5 1/3] CXL, PCIE: Add cxl_rcrb_addr file to dport_dev

[Ben Cheatham <Benjamin.Cheatham@amd.com>]

Add cxl_rcrb_addr to the dport_dev (normally represented by a pcie
device) for CXL RCH root ports. The file will print the RCRB base
MMIO address of the root port when read and will be used by
users looking to inject CXL EINJ error types for RCH hosts.

Signed-off-by: Ben Cheatham <Benjamin.Cheatham@amd.com>
---
 Documentation/ABI/testing/sysfs-bus-cxl |  9 ++++
 drivers/cxl/acpi.c                      |  2 +
 drivers/cxl/core/port.c                 | 58 +++++++++++++++++++++++++
 drivers/cxl/cxl.h                       |  2 +
 4 files changed, 71 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-bus-cxl b/Documentation/ABI/testing/sysfs-bus-cxl
index 087f762ebfd5..85621da69296 100644
--- a/Documentation/ABI/testing/sysfs-bus-cxl
+++ b/Documentation/ABI/testing/sysfs-bus-cxl
@@ -177,6 +177,15 @@ Description:
 		integer reflects the hardware port unique-id used in the
 		hardware decoder target list.
 
+What:		/sys/bus/cxl/devices/portX/dportY/cxl_rcrb_addr
+What:		/sys/devices/pciX/cxl_rcrb_addr
+Date:		August, 2023
+KernelVersion:	v6.6
+Contact:	linux-cxl@vger.kernel.org
+Description:
+		(RO) The 'cxl_rcrb_addr' device file gives the MMIO base address
+		of the RCRB of the corresponding CXL 1.1 downstream port. Only
+		present for CXL 1.1 dports.
 
 What:		/sys/bus/cxl/devices/decoderX.Y
 Date:		June, 2021
diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c
index d1c559879dcc..3e2ca946bf47 100644
--- a/drivers/cxl/acpi.c
+++ b/drivers/cxl/acpi.c
@@ -676,6 +676,8 @@ static int cxl_acpi_probe(struct platform_device *pdev)
 	if (IS_ERR(root_port))
 		return PTR_ERR(root_port);
 
+	set_cxl_root(root_port);
+
 	rc = bus_for_each_dev(adev->dev.bus, NULL, root_port,
 			      add_host_bridge_dport);
 	if (rc < 0)
diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
index 724be8448eb4..c3914e73f67e 100644
--- a/drivers/cxl/core/port.c
+++ b/drivers/cxl/core/port.c
@@ -875,6 +875,14 @@ struct cxl_port *find_cxl_root(struct cxl_port *port)
 }
 EXPORT_SYMBOL_NS_GPL(find_cxl_root, CXL);
 
+static struct cxl_port *cxl_root;
+
+void set_cxl_root(struct cxl_port *root_port)
+{
+	cxl_root = root_port;
+}
+EXPORT_SYMBOL_NS_GPL(set_cxl_root, CXL);
+
 static struct cxl_dport *find_dport(struct cxl_port *port, int id)
 {
 	struct cxl_dport *dport;
@@ -930,11 +938,56 @@ static void cond_cxl_root_unlock(struct cxl_port *port)
 		device_unlock(&port->dev);
 }
 
+static ssize_t cxl_rcrb_addr_show(struct device *dev,
+				  struct device_attribute *attr, char *buf)
+{
+	struct cxl_dport *dport;
+
+	if (!cxl_root)
+		return -ENODEV;
+
+	dport = cxl_find_dport_by_dev(cxl_root, dev);
+	if (!dport)
+		return -ENODEV;
+
+	return sysfs_emit(buf, "0x%llx\n", (u64) dport->rcrb.base);
+}
+DEVICE_ATTR_RO(cxl_rcrb_addr);
+
+static umode_t cxl_rcrb_addr_is_visible(struct kobject *kobj,
+					struct attribute *a, int n)
+{
+	struct device *dev = kobj_to_dev(kobj);
+	struct cxl_dport *dport;
+
+	if (!IS_ENABLED(CONFIG_ACPI_APEI_EINJ) || !cxl_root)
+		return 0;
+
+	dport = cxl_find_dport_by_dev(cxl_root, dev);
+	if (!dport || !dport->rch || dport->rcrb.base == CXL_RESOURCE_NONE)
+		return 0;
+
+	return a->mode;
+}
+
+static struct attribute *cxl_rcrb_addr_attrs[] = {
+	&dev_attr_cxl_rcrb_addr.attr,
+	NULL,
+};
+
+static const struct attribute_group cxl_rcrb_addr_group = {
+	.attrs = cxl_rcrb_addr_attrs,
+	.is_visible = cxl_rcrb_addr_is_visible,
+};
+
 static void cxl_dport_remove(void *data)
 {
 	struct cxl_dport *dport = data;
 	struct cxl_port *port = dport->port;
 
+	if (dport->rch)
+		sysfs_remove_group(&dport->dport_dev->kobj, &cxl_rcrb_addr_group);
+
 	xa_erase(&port->dports, (unsigned long) dport->dport_dev);
 	put_device(dport->dport_dev);
 }
@@ -1021,6 +1074,11 @@ __devm_cxl_add_dport(struct cxl_port *port, struct device *dport_dev,
 	if (rc)
 		return ERR_PTR(rc);
 
+	rc = sysfs_create_group(&dport_dev->kobj, &cxl_rcrb_addr_group);
+	if (rc)
+		dev_dbg(dport_dev, "Couldn't create cxl_rcrb_addr group: %d\n",
+			rc);
+
 	return dport;
 }
 
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 76d92561af29..4d5bce4bae7e 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -690,6 +690,8 @@ struct cxl_port *devm_cxl_add_port(struct device *host,
 				   resource_size_t component_reg_phys,
 				   struct cxl_dport *parent_dport);
 struct cxl_port *find_cxl_root(struct cxl_port *port);
+void set_cxl_root(struct cxl_port *root_port);
+
 int devm_cxl_enumerate_ports(struct cxl_memdev *cxlmd);
 void cxl_bus_rescan(void);
 void cxl_bus_drain(void);
-- 
2.34.1