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authorDave Jiang <dave.jiang@intel.com>2023-12-21 15:04:04 -0700
committerDan Williams <dan.j.williams@intel.com>2023-12-22 15:31:52 -0800
commit7a4f148dd8d518bc1e012aa738b0ed6244959293 (patch)
tree770b44877ad42135313454cd90bccd1b7e037a72 /drivers/cxl
parent14a6960b3e928ccea22d687fb0626237885a20bd (diff)
downloadlwn-7a4f148dd8d518bc1e012aa738b0ed6244959293.tar.gz
lwn-7a4f148dd8d518bc1e012aa738b0ed6244959293.zip
cxl: Compute the entire CXL path latency and bandwidth data
CXL Memory Device SW Guide [1] rev1.0 2.11.2 provides instruction on how to calculate latency and bandwidth for CXL memory device. Calculate minimum bandwidth and total latency for the path from the CXL device to the root port. The QTG id is retrieved by providing the performance data as input and calling the root port callback ->get_qos_class(). The retrieved id is stored with the cxl_port of the CXL device. For example for a device that is directly attached to a host bus: Total Latency = Device Latency (from CDAT) + Dev to Host Bus (HB) Link Latency + Generic Port Latency Min Bandwidth = Min bandwidth for link bandwidth between HB and CXL device, device CDAT bandwidth, and Generic Port Bandwidth For a device that has a switch in between host bus and CXL device: Total Latency = Device (CDAT) Latency + Dev to Switch Link Latency + Switch (CDAT) Latency + Switch to HB Link Latency + Generic Port Latency Min Bandwidth = Min bandwidth for link bandwidth between CXL device to CXL switch, CXL device CDAT bandwidth, CXL switch CDAT bandwidth, CXL switch to HB bandwidth, and Generic Port Bandwidth. [1]: https://cdrdv2-public.intel.com/643805/643805_CXL%20Memory%20Device%20SW%20Guide_Rev1p0.pdf Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> Signed-off-by: Dave Jiang <dave.jiang@intel.com> Link: https://lore.kernel.org/r/170319624458.2212653.13252496567443656371.stgit@djiang5-mobl3 Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Diffstat (limited to 'drivers/cxl')
-rw-r--r--drivers/cxl/core/cdat.c59
1 files changed, 58 insertions, 1 deletions
diff --git a/drivers/cxl/core/cdat.c b/drivers/cxl/core/cdat.c
index b3ab47d250e1..43dfef80fb84 100644
--- a/drivers/cxl/core/cdat.c
+++ b/drivers/cxl/core/cdat.c
@@ -12,6 +12,9 @@ struct dsmas_entry {
struct range dpa_range;
u8 handle;
struct access_coordinate coord;
+
+ int entries;
+ int qos_class;
};
static int cdat_dsmas_handler(union acpi_subtable_headers *header, void *arg,
@@ -154,6 +157,55 @@ static int cxl_cdat_endpoint_process(struct cxl_port *port,
return cdat_table_parse_output(rc);
}
+static int cxl_port_perf_data_calculate(struct cxl_port *port,
+ struct xarray *dsmas_xa)
+{
+ struct access_coordinate c;
+ struct cxl_port *root_port;
+ struct cxl_root *cxl_root;
+ struct dsmas_entry *dent;
+ int valid_entries = 0;
+ unsigned long index;
+ int rc;
+
+ rc = cxl_endpoint_get_perf_coordinates(port, &c);
+ if (rc) {
+ dev_dbg(&port->dev, "Failed to retrieve perf coordinates.\n");
+ return rc;
+ }
+
+ root_port = find_cxl_root(port);
+ cxl_root = to_cxl_root(root_port);
+ if (!cxl_root->ops || !cxl_root->ops->qos_class)
+ return -EOPNOTSUPP;
+
+ xa_for_each(dsmas_xa, index, dent) {
+ int qos_class;
+
+ dent->coord.read_latency = dent->coord.read_latency +
+ c.read_latency;
+ dent->coord.write_latency = dent->coord.write_latency +
+ c.write_latency;
+ dent->coord.read_bandwidth = min_t(int, c.read_bandwidth,
+ dent->coord.read_bandwidth);
+ dent->coord.write_bandwidth = min_t(int, c.write_bandwidth,
+ dent->coord.write_bandwidth);
+
+ dent->entries = 1;
+ rc = cxl_root->ops->qos_class(root_port, &dent->coord, 1, &qos_class);
+ if (rc != 1)
+ continue;
+
+ valid_entries++;
+ dent->qos_class = qos_class;
+ }
+
+ if (!valid_entries)
+ return -ENOENT;
+
+ return 0;
+}
+
static void discard_dsmas(struct xarray *xa)
{
unsigned long index;
@@ -183,7 +235,12 @@ void cxl_endpoint_parse_cdat(struct cxl_port *port)
return;
}
- /* Performance data processing */
+ rc = cxl_port_perf_data_calculate(port, dsmas_xa);
+ if (rc) {
+ dev_dbg(&port->dev, "Failed to do perf coord calculations.\n");
+ return;
+ }
+
}
EXPORT_SYMBOL_NS_GPL(cxl_endpoint_parse_cdat, CXL);