[PATCH v4 23/23] cxl/mem: Add debugfs output for QTG related data

[Dave Jiang <dave.jiang@xxxxxxxxx>]

Add debugfs output to /sys/kernel/debug/cxl/memX/qtgmap
The debugfs attribute will dump out all the DSMAS ranges and the associated
QTG ID exported by the CXL device CDAT.

Suggested-by: Dan Williams <dan.j.williams@xxxxxxxxx>
Signed-off-by: Dave Jiang <dave.jiang@xxxxxxxxx>

---
v4:
- Use cxlds->qos_list instead of the stray cxlmd->qos_list
---
 Documentation/ABI/testing/debugfs-cxl |   11 +++++++++++
 drivers/cxl/mem.c                     |   17 +++++++++++++++++
 2 files changed, 28 insertions(+)
 create mode 100644 Documentation/ABI/testing/debugfs-cxl

diff --git a/Documentation/ABI/testing/debugfs-cxl b/Documentation/ABI/testing/debugfs-cxl
new file mode 100644
index 000000000000..0f36eeb7e59b
--- /dev/null
+++ b/Documentation/ABI/testing/debugfs-cxl
@@ -0,0 +1,11 @@
+What:		/sys/kernel/debug/cxl/memX/qtg_map
+Date:		Mar, 2023
+KernelVersion:	v6.4
+Contact:	linux-cxl@xxxxxxxxxxxxxxx
+Description:
+		(RO) Entries of all Device Physical Address (DPA) ranges
+		provided by the device Coherent Device Attributes Table (CDAT)
+		Device Scoped Memory Affinity Structure (DSMAS) entries with
+		the matching QoS Throttling Group (QTG) id calculated from the
+		latency and bandwidth of the CXL path from the memory device
+		to the CPU.
diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
index 39c4b54f0715..9a23875975eb 100644
--- a/drivers/cxl/mem.c
+++ b/drivers/cxl/mem.c
@@ -45,6 +45,22 @@ static int cxl_mem_dpa_show(struct seq_file *file, void *data)
 	return 0;
 }
 
+static int cxl_mem_qtg_show(struct seq_file *file, void *data)
+{
+	struct device *dev = file->private;
+	struct cxl_memdev *cxlmd = to_cxl_memdev(dev);
+	struct cxl_dev_state *cxlds = cxlmd->cxlds;
+	struct qos_prop_entry *qos;
+
+	list_for_each_entry(qos, &cxlds->qos_list, list) {
+		seq_printf(file, "%08llx-%08llx : QTG ID %u\n",
+			   qos->dpa_range.start, qos->dpa_range.end,
+			   qos->qtg_id);
+	}
+
+	return 0;
+}
+
 static int devm_cxl_add_endpoint(struct device *host, struct cxl_memdev *cxlmd,
 				 struct cxl_dport *parent_dport)
 {
@@ -117,6 +133,7 @@ static int cxl_mem_probe(struct device *dev)
 
 	dentry = cxl_debugfs_create_dir(dev_name(dev));
 	debugfs_create_devm_seqfile(dev, "dpamem", dentry, cxl_mem_dpa_show);
+	debugfs_create_devm_seqfile(dev, "qtgmap", dentry, cxl_mem_qtg_show);
 	rc = devm_add_action_or_reset(dev, remove_debugfs, dentry);
 	if (rc)
 		return rc;