[PATCH v2 15/21] cxl: Add helper function to retrieve generic port QoS

[Dave Jiang <dave.jiang@xxxxxxxxx>]

Add CXL helper function that retrieves the bandwidth and latency data of a
generic port by calling acpi_get_genport_attrs() function. A device handle
is passed in constructed from the ACPI HID and UID of the CXL host bridge
(ACPI0016) device.

Signed-off-by: Dave Jiang <dave.jiang@xxxxxxxxx>
---
 drivers/cxl/core/acpi.c |   30 ++++++++++++++++++++++++++++++
 drivers/cxl/cxl.h       |    1 +
 2 files changed, 31 insertions(+)

diff --git a/drivers/cxl/core/acpi.c b/drivers/cxl/core/acpi.c
index 191644d0ca6d..41eeaa8c272e 100644
--- a/drivers/cxl/core/acpi.c
+++ b/drivers/cxl/core/acpi.c
@@ -148,3 +148,33 @@ struct qtg_dsm_output *cxl_acpi_evaluate_qtg_dsm(acpi_handle handle,
 	return ERR_PTR(rc);
 }
 EXPORT_SYMBOL_NS_GPL(cxl_acpi_evaluate_qtg_dsm, CXL);
+
+/**
+ * cxl_acpi_get_hb_qos - retrieve QoS data for generic port
+ * @host: 'struct device' of the CXL host bridge
+ * @latency: genport latency data
+ * @bandwidth: genport bandwidth data
+ *
+ * Return: Errno on failure, 0 on success.
+ */
+int cxl_acpi_get_hb_qos(struct device *host, u64 *latency, u64 *bandwidth)
+{
+	u8 handle[ACPI_SRAT_DEVICE_HANDLE_SIZE] = { 0 };
+	struct acpi_device *adev = ACPI_COMPANION(host);
+	int rc;
+
+	/* ACPI spec 6.5 Table 5.65 */
+	memcpy(handle, acpi_device_hid(adev), 8);
+	memcpy(&handle[8], acpi_device_uid(adev), 4);
+
+	rc = acpi_get_genport_attrs(handle, latency, ACPI_HMAT_ACCESS_LATENCY);
+	if (rc)
+		return rc;
+
+	rc = acpi_get_genport_attrs(handle, bandwidth, ACPI_HMAT_ACCESS_BANDWIDTH);
+	if (rc)
+		return rc;
+
+	return 0;
+}
+EXPORT_SYMBOL_NS_GPL(cxl_acpi_get_hb_qos, CXL);
diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
index 67e844645ef6..56bcf144eede 100644
--- a/drivers/cxl/cxl.h
+++ b/drivers/cxl/cxl.h
@@ -811,6 +811,7 @@ int cxl_port_get_switch_qos(struct cxl_port *port, u64 *rd_bw, u64 *rd_lat,
 			    u64 *wr_bw, u64 *wr_lat);
 int cxl_port_get_downstream_qos(struct cxl_port *port, u64 *bandwidth,
 				u64 *latency);
+int cxl_acpi_get_hb_qos(struct device *host, u64 *latency, u64 *bandwidth);
 
 /*
  * Unit test builds overrides this to __weak, find the 'strong' version