1*4cdadfd5SDan Williams# SPDX-License-Identifier: GPL-2.0-only 2*4cdadfd5SDan Williamsmenuconfig CXL_BUS 3*4cdadfd5SDan Williams tristate "CXL (Compute Express Link) Devices Support" 4*4cdadfd5SDan Williams depends on PCI 5*4cdadfd5SDan Williams help 6*4cdadfd5SDan Williams CXL is a bus that is electrically compatible with PCI Express, but 7*4cdadfd5SDan Williams layers three protocols on that signalling (CXL.io, CXL.cache, and 8*4cdadfd5SDan Williams CXL.mem). The CXL.cache protocol allows devices to hold cachelines 9*4cdadfd5SDan Williams locally, the CXL.mem protocol allows devices to be fully coherent 10*4cdadfd5SDan Williams memory targets, the CXL.io protocol is equivalent to PCI Express. 11*4cdadfd5SDan Williams Say 'y' to enable support for the configuration and management of 12*4cdadfd5SDan Williams devices supporting these protocols. 13*4cdadfd5SDan Williams 14*4cdadfd5SDan Williamsif CXL_BUS 15*4cdadfd5SDan Williams 16*4cdadfd5SDan Williamsconfig CXL_MEM 17*4cdadfd5SDan Williams tristate "CXL.mem: Memory Devices" 18*4cdadfd5SDan Williams help 19*4cdadfd5SDan Williams The CXL.mem protocol allows a device to act as a provider of 20*4cdadfd5SDan Williams "System RAM" and/or "Persistent Memory" that is fully coherent 21*4cdadfd5SDan Williams as if the memory was attached to the typical CPU memory 22*4cdadfd5SDan Williams controller. 23*4cdadfd5SDan Williams 24*4cdadfd5SDan Williams Say 'y/m' to enable a driver (named "cxl_mem.ko" when built as 25*4cdadfd5SDan Williams a module) that will attach to CXL.mem devices for 26*4cdadfd5SDan Williams configuration, provisioning, and health monitoring. This 27*4cdadfd5SDan Williams driver is required for dynamic provisioning of CXL.mem 28*4cdadfd5SDan Williams attached memory which is a prerequisite for persistent memory 29*4cdadfd5SDan Williams support. Typically volatile memory is mapped by platform 30*4cdadfd5SDan Williams firmware and included in the platform memory map, but in some 31*4cdadfd5SDan Williams cases the OS is responsible for mapping that memory. See 32*4cdadfd5SDan Williams Chapter 2.3 Type 3 CXL Device in the CXL 2.0 specification. 33*4cdadfd5SDan Williams 34*4cdadfd5SDan Williams If unsure say 'm'. 35*4cdadfd5SDan Williamsendif 36