From c97006046c791f82cb5ba3219ef4a511ec5f3932 Mon Sep 17 00:00:00 2001 From: Ira Weiny Date: Tue, 19 Jul 2022 13:52:49 -0700 Subject: cxl/port: Read CDAT table The per-device CDAT data provides performance data that is relevant for mapping which CXL devices can participate in which CXL ranges by QTG (QoS Throttling Group) (per ECN: CXL 2.0 CEDT CFMWS & QTG_DSM) [1]. The QTG association specified in the ECN is advisory. Until the cxl_acpi driver grows support for invoking the QTG _DSM method the CDAT data is only of interest to userspace that may need it for debug purposes. Search the DOE mailboxes available, query CDAT data, cache the data and make it available via a sysfs binary attribute per endpoint at: /sys/bus/cxl/devices/endpointX/CDAT ...similar to other ACPI-structured table data in /sys/firmware/ACPI/tables. The CDAT is relative to 'struct cxl_port' objects since switches in addition to endpoints can host a CDAT instance. Switch CDAT support is not implemented. This does not support table updates at runtime. It will always provide whatever was there when first cached. It is also the case that table updates are not expected outside of explicit DPA address map affecting commands like Set Partition with the immediate flag set. Given that the driver does not support Set Partition with the immediate flag set there is no current need for update support. Link: https://www.computeexpresslink.org/spec-landing [1] Signed-off-by: Jonathan Cameron Co-developed-by: Jonathan Cameron Signed-off-by: Ira Weiny [djbw: drop in-kernel parsing infra for now, and other minor fixups] Reviewed-by: Jonathan Cameron Link: https://lore.kernel.org/r/20220719205249.566684-7-ira.weiny@intel.com Signed-off-by: Dan Williams --- Documentation/ABI/testing/sysfs-bus-cxl | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'Documentation/ABI/testing') diff --git a/Documentation/ABI/testing/sysfs-bus-cxl b/Documentation/ABI/testing/sysfs-bus-cxl index 1fd5984b6158..e94c5aebc368 100644 --- a/Documentation/ABI/testing/sysfs-bus-cxl +++ b/Documentation/ABI/testing/sysfs-bus-cxl @@ -164,3 +164,13 @@ Description: expander memory (type-3). The 'target_type' attribute indicates the current setting which may dynamically change based on what memory regions are activated in this decode hierarchy. + +What: /sys/bus/cxl/devices/endpointX/CDAT +Date: July, 2022 +KernelVersion: v5.20 +Contact: linux-cxl@vger.kernel.org +Description: + (RO) If this sysfs entry is not present no DOE mailbox was + found to support CDAT data. If it is present and the length of + the data is 0 reading the CDAT data failed. Otherwise the CDAT + data is reported. -- cgit v1.2.3