new file mode 100644
@@ -0,0 +1,12 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+====================
+Compute Express Link
+====================
+
+.. toctree::
+ :maxdepth: 1
+
+ memory-devices
+
+.. only:: subproject and html
new file mode 100644
@@ -0,0 +1,29 @@
+.. 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:
@@ -35,6 +35,7 @@ available subsections can be seen below.
usb/index
firewire
pci/index
+ cxl/index
spi
i2c
ipmb
@@ -6,6 +6,7 @@ menu "Device Drivers"
source "drivers/amba/Kconfig"
source "drivers/eisa/Kconfig"
source "drivers/pci/Kconfig"
+source "drivers/cxl/Kconfig"
source "drivers/pcmcia/Kconfig"
source "drivers/rapidio/Kconfig"
@@ -73,6 +73,7 @@ obj-$(CONFIG_NVM) += lightnvm/
obj-y += base/ block/ misc/ mfd/ nfc/
obj-$(CONFIG_LIBNVDIMM) += nvdimm/
obj-$(CONFIG_DAX) += dax/
+obj-$(CONFIG_CXL_BUS) += cxl/
obj-$(CONFIG_DMA_SHARED_BUFFER) += dma-buf/
obj-$(CONFIG_NUBUS) += nubus/
obj-y += macintosh/
new file mode 100644
@@ -0,0 +1,35 @@
+# SPDX-License-Identifier: GPL-2.0-only
+menuconfig CXL_BUS
+ tristate "CXL (Compute Express Link) Devices Support"
+ depends on PCI
+ help
+ CXL is a bus that is electrically compatible with PCI Express, but
+ layers three protocols on that signalling (CXL.io, CXL.cache, and
+ CXL.mem). The CXL.cache protocol allows devices to hold cachelines
+ locally, the CXL.mem protocol allows devices to be fully coherent
+ memory targets, the CXL.io protocol is equivalent to PCI Express.
+ Say 'y' to enable support for the configuration and management of
+ devices supporting these protocols.
+
+if CXL_BUS
+
+config CXL_MEM
+ tristate "CXL.mem: Memory Devices"
+ help
+ The CXL.mem protocol allows a device to act as a provider of
+ "System RAM" and/or "Persistent Memory" that is fully coherent
+ as if the memory was attached to the typical CPU memory
+ controller.
+
+ Say 'y/m' to enable a driver (named "cxl_mem.ko" when built as
+ a module) that will attach to CXL.mem devices for
+ configuration, provisioning, and health monitoring. This
+ driver is required for dynamic provisioning of CXL.mem
+ attached memory which is a prerequisite for persistent memory
+ support. Typically volatile memory is mapped by platform
+ firmware and included in the platform memory map, but in some
+ cases the OS is responsible for mapping that memory. See
+ Chapter 2.3 Type 3 CXL Device in the CXL 2.0 specification.
+
+ If unsure say 'm'.
+endif
new file mode 100644
@@ -0,0 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0
+obj-$(CONFIG_CXL_MEM) += cxl_mem.o
+
+cxl_mem-y := mem.o
new file mode 100644
@@ -0,0 +1,62 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* Copyright(c) 2020 Intel Corporation. All rights reserved. */
+#include <linux/module.h>
+#include <linux/pci.h>
+#include <linux/io.h>
+#include "pci.h"
+
+static int cxl_mem_dvsec(struct pci_dev *pdev, int dvsec)
+{
+ int pos;
+
+ pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_DVSEC);
+ if (!pos)
+ return 0;
+
+ while (pos) {
+ u16 vendor, id;
+
+ pci_read_config_word(pdev, pos + PCI_DVSEC_HEADER1, &vendor);
+ pci_read_config_word(pdev, pos + PCI_DVSEC_HEADER2, &id);
+ if (vendor == PCI_DVSEC_VENDOR_ID_CXL && dvsec == id)
+ return pos;
+
+ pos = pci_find_next_ext_capability(pdev, pos,
+ PCI_EXT_CAP_ID_DVSEC);
+ }
+
+ return 0;
+}
+
+static int cxl_mem_probe(struct pci_dev *pdev, const struct pci_device_id *id)
+{
+ struct device *dev = &pdev->dev;
+ int regloc;
+
+ regloc = cxl_mem_dvsec(pdev, PCI_DVSEC_ID_CXL_REGLOC_OFFSET);
+ if (!regloc) {
+ dev_err(dev, "register location dvsec not found\n");
+ return -ENXIO;
+ }
+
+ return 0;
+}
+
+static const struct pci_device_id cxl_mem_pci_tbl[] = {
+ /* PCI class code for CXL.mem Type-3 Devices */
+ { PCI_DEVICE_CLASS((PCI_CLASS_MEMORY_CXL << 8 | CXL_MEMORY_PROGIF), ~0)},
+ { /* terminate list */ },
+};
+MODULE_DEVICE_TABLE(pci, cxl_mem_pci_tbl);
+
+static struct pci_driver cxl_mem_driver = {
+ .name = KBUILD_MODNAME,
+ .id_table = cxl_mem_pci_tbl,
+ .probe = cxl_mem_probe,
+ .driver = {
+ .probe_type = PROBE_PREFER_ASYNCHRONOUS,
+ },
+};
+
+MODULE_LICENSE("GPL v2");
+module_pci_driver(cxl_mem_driver);
new file mode 100644
@@ -0,0 +1,17 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/* Copyright(c) 2020 Intel Corporation. All rights reserved. */
+#ifndef __CXL_PCI_H__
+#define __CXL_PCI_H__
+
+#define CXL_MEMORY_PROGIF 0x10
+
+/*
+ * See section 8.1 Configuration Space Registers in the CXL 2.0
+ * Specification
+ */
+#define PCI_DVSEC_VENDOR_ID_CXL 0x1E98
+#define PCI_DVSEC_ID_CXL 0x0
+
+#define PCI_DVSEC_ID_CXL_REGLOC_OFFSET 0x8
+
+#endif /* __CXL_PCI_H__ */
@@ -51,6 +51,7 @@
#define PCI_BASE_CLASS_MEMORY 0x05
#define PCI_CLASS_MEMORY_RAM 0x0500
#define PCI_CLASS_MEMORY_FLASH 0x0501
+#define PCI_CLASS_MEMORY_CXL 0x0502
#define PCI_CLASS_MEMORY_OTHER 0x0580
#define PCI_BASE_CLASS_BRIDGE 0x06