[PATCH v3 30/40] cxl/pci: Emit device serial number

[Dan Williams <dan.j.williams@intel.com>]

Per the CXL specification (8.1.12.2 Memory Device PCIe Capabilities and
Extended Capabilities) the Device Serial Number capability is mandatory.
Emit it for user tooling to identify devices.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 Documentation/ABI/testing/sysfs-bus-cxl |    9 +++++++++
 drivers/cxl/core/memdev.c               |   11 +++++++++++
 drivers/cxl/cxlmem.h                    |    2 ++
 drivers/cxl/pci.c                       |    1 +
 tools/testing/cxl/test/mem.c            |    1 +
 5 files changed, 24 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-bus-cxl b/Documentation/ABI/testing/sysfs-bus-cxl
index 6d8cbf3355b5..87c0e5e65322 100644
--- a/Documentation/ABI/testing/sysfs-bus-cxl
+++ b/Documentation/ABI/testing/sysfs-bus-cxl
@@ -25,6 +25,15 @@ Description:
 		identically named field in the Identify Memory Device Output
 		Payload in the CXL-2.0 specification.
 
+What:		/sys/bus/cxl/devices/memX/serial
+Date:		January, 2022
+KernelVersion:	v5.18
+Contact:	linux-cxl@vger.kernel.org
+Description:
+		(RO) 64-bit serial number per the PCIe Device Serial Number
+		capability. Mandatory for CXL devices, see CXL 2.0 8.1.12.2
+		Memory Device PCIe Capabilities and Extended Capabilities.
+
 What:		/sys/bus/cxl/devices/*/devtype
 Date:		June, 2021
 KernelVersion:	v5.14
diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c
index 61029cb7ac62..1e574b052583 100644
--- a/drivers/cxl/core/memdev.c
+++ b/drivers/cxl/core/memdev.c
@@ -89,7 +89,18 @@ static ssize_t pmem_size_show(struct device *dev, struct device_attribute *attr,
 static struct device_attribute dev_attr_pmem_size =
 	__ATTR(size, 0444, pmem_size_show, NULL);
 
+static ssize_t serial_show(struct device *dev, struct device_attribute *attr,
+			   char *buf)
+{
+	struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
+	struct cxl_dev_state *cxlds = cxlmd->cxlds;
+
+	return sysfs_emit(buf, "%#llx\n", cxlds->serial);
+}
+static DEVICE_ATTR_RO(serial);
+
 static struct attribute *cxl_memdev_attributes[] = {
+	&dev_attr_serial.attr,
 	&dev_attr_firmware_version.attr,
 	&dev_attr_payload_max.attr,
 	&dev_attr_label_storage_size.attr,
diff --git a/drivers/cxl/cxlmem.h b/drivers/cxl/cxlmem.h
index e70838e5dc17..0ba0cf8dcdbc 100644
--- a/drivers/cxl/cxlmem.h
+++ b/drivers/cxl/cxlmem.h
@@ -131,6 +131,7 @@ struct cxl_endpoint_dvsec_info {
  * @next_persistent_bytes: persistent capacity change pending device reset
  * @component_reg_phys: register base of component registers
  * @info: Cached DVSEC information about the device.
+ * @serial: PCIe Device Serial Number
  * @mbox_send: @dev specific transport for transmitting mailbox commands
  * @wait_media_ready: @dev specific method to await media ready
  *
@@ -164,6 +165,7 @@ struct cxl_dev_state {
 
 	resource_size_t component_reg_phys;
 	struct cxl_endpoint_dvsec_info info;
+	u64 serial;
 
 	int (*mbox_send)(struct cxl_dev_state *cxlds, struct cxl_mbox_cmd *cmd);
 	int (*wait_media_ready)(struct cxl_dev_state *cxlds);
diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
index 513cb0e2a70a..9252e1f4b18c 100644
--- a/drivers/cxl/pci.c
+++ b/drivers/cxl/pci.c
@@ -557,6 +557,7 @@ static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 	if (IS_ERR(cxlds))
 		return PTR_ERR(cxlds);
 
+	cxlds->serial = pci_get_dsn(pdev);
 	cxlds->cxl_dvsec = pci_find_dvsec_capability(
 		pdev, PCI_DVSEC_VENDOR_ID_CXL, CXL_DVSEC);
 	if (!cxlds->cxl_dvsec) {
diff --git a/tools/testing/cxl/test/mem.c b/tools/testing/cxl/test/mem.c
index 3af3f94de0c3..36ef337c775c 100644
--- a/tools/testing/cxl/test/mem.c
+++ b/tools/testing/cxl/test/mem.c
@@ -268,6 +268,7 @@ static int cxl_mock_mem_probe(struct platform_device *pdev)
 	if (IS_ERR(cxlds))
 		return PTR_ERR(cxlds);
 
+	cxlds->serial = pdev->id;
 	cxlds->mbox_send = cxl_mock_mbox_send;
 	cxlds->wait_media_ready = cxl_mock_wait_media_ready;
 	cxlds->payload_size = SZ_4K;