Merge tag 'cxl-for-5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm

Pull initial support for CXL (Compute Express Link) from Dan Williams:
 "Introduce an initial driver for CXL 2.0 Type-3 Memory Devices.

  CXL is Compute Express Link which released the 2.0 specification in
  November. The Linux relevant changes in CXL 2.0 are support for an OS
  to dynamically assign address space to memory devices, support for
  switches, persistent memory, and hotplug.

  A Type-3 Memory Device is a PCI enumerated device presenting the CXL
  Memory Device Class Code and implementing the CXL.mem protocol.
  CXL.mem allows device to advertise CPU and I/O coherent memory to the
  system, i.e. typical "System RAM" and "Persistent Memory" in Linux
  /proc/iomem terms.

  In addition to the CXL.mem fast path there is an administrative
  command hardware mailbox interface for maintenance and provisioning.
  It is this command interface that is the focus of the initial driver.
  With this driver a CXL device that is mapped by the BIOS can be
  administered by Linux.

  Linux support for CXL PMEM and dynamic CXL address space management
  are to be implemented post v5.12"

Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
  4cdadfd5e0a7 ("cxl/mem: Introduce a driver for CXL-2.0-Type-3 endpoints")
  13237183c735 ("cxl/mem: Add a "RAW" send command")
  472b1ce6e9d6 ("cxl/mem: Enable commands via CEL")
  57ee605b976c ("cxl/mem: Add set of informational commands")

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
  8adaf747c9f0 ("cxl/mem: Find device capabilities")
  b39cb1052a5c ("cxl/mem: Register CXL memX devices")

* tag 'cxl-for-5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm:
  cxl/mem: Fix potential memory leak
  cxl/mem: Return -EFAULT if copy_to_user() fails
  MAINTAINERS: Add maintainers of the CXL driver
  cxl/mem: Add set of informational commands
  cxl/mem: Enable commands via CEL
  cxl/mem: Add a "RAW" send command
  cxl/mem: Add basic IOCTL interface
  cxl/mem: Register CXL memX devices
  cxl/mem: Find device capabilities
  cxl/mem: Introduce a driver for CXL-2.0-Type-3 endpoints

3 files changed, 59 insertions, 0 deletions

diff --git a/Documentation/driver-api/cxl/index.rst b/Documentation/driver-api/cxl/index.rst
new file mode 100644
index 000000000000..036e49553542
--- /dev/null
+++ b/Documentation/driver-api/cxl/index.rst
@@ -0,0 +1,12 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+====================
+Compute Express Link
+====================
+
+.. toctree::
+   :maxdepth: 1
+
+   memory-devices
+
+.. only::  subproject and html
diff --git a/Documentation/driver-api/cxl/memory-devices.rst b/Documentation/driver-api/cxl/memory-devices.rst
new file mode 100644
index 000000000000..1bad466f9167
--- /dev/null
+++ b/Documentation/driver-api/cxl/memory-devices.rst
@@ -0,0 +1,46 @@
+.. SPDX-License-Identifier: GPL-2.0
+.. include:: <isonum.txt>
+
+===================================
+Compute Express Link Memory Devices
+===================================
+
+A Compute Express Link Memory Device is a CXL component that implements the
+CXL.mem protocol. It contains some amount of volatile memory, persistent memory,
+or both. It is enumerated as a PCI device for configuration and passing
+messages over an MMIO mailbox. Its contribution to the System Physical
+Address space is handled via HDM (Host Managed Device Memory) decoders
+that optionally define a device's contribution to an interleaved address
+range across multiple devices underneath a host-bridge or interleaved
+across host-bridges.
+
+Driver Infrastructure
+=====================
+
+This section covers the driver infrastructure for a CXL memory device.
+
+CXL Memory Device
+-----------------
+
+.. kernel-doc:: drivers/cxl/mem.c
+   :doc: cxl mem
+
+.. kernel-doc:: drivers/cxl/mem.c
+   :internal:
+
+CXL Bus
+-------
+.. kernel-doc:: drivers/cxl/bus.c
+   :doc: cxl bus
+
+External Interfaces
+===================
+
+CXL IOCTL Interface
+-------------------
+
+.. kernel-doc:: include/uapi/linux/cxl_mem.h
+   :doc: UAPI
+
+.. kernel-doc:: include/uapi/linux/cxl_mem.h
+   :internal:
diff --git a/Documentation/driver-api/index.rst b/Documentation/driver-api/index.rst
index 9d9af54d68c5..9ba74e86751b 100644
--- a/Documentation/driver-api/index.rst
+++ b/Documentation/driver-api/index.rst
@@ -35,6 +35,7 @@ available subsections can be seen below.
    usb/index
    firewire
    pci/index
+   cxl/index
    spi
    i2c
    ipmb