#
  # Copyright (C) 2017 NXP Semiconductors
  # Copyright (C) 2017 Bin Meng <bmeng.cn@gmail.com>
  #
  # SPDX-License-Identifier:	GPL-2.0+
  #
  
  What is NVMe
  ============
  
  NVM Express (NVMe) is a register level interface that allows host software to
  communicate with a non-volatile memory subsystem. This interface is optimized
  for enterprise and client solid state drives, typically attached to the PCI
  express interface. It is a scalable host controller interface designed to
  address the needs of enterprise and client systems that utilize PCI express
  based solid state drives (SSD). The interface provides optimized command
  submission and completion paths. It includes support for parallel operation by
  supporting up to 64K I/O queues with up to 64K commands per I/O queue.
  
  The device is comprised of some number of controllers, where each controller
  is comprised of some number of namespaces, where each namespace is comprised
  of some number of logical blocks. A namespace is a quantity of non-volatile
  memory that is formatted into logical blocks. An NVMe namespace is equivalent
  to a SCSI LUN. Each namespace is operated as an independent "device".
  
  How it works
  ------------
  There is an NVMe uclass driver (driver name "nvme"), an NVMe host controller
  driver (driver name "nvme") and an NVMe namespace block driver (driver name
  "nvme-blk"). The host controller driver is supposed to probe the hardware and
  do necessary initialization to put the controller into a ready state at which
  it is able to scan all available namespaces attached to it. Scanning namespace
  is triggered by the NVMe uclass driver and the actual work is done in the NVMe
  namespace block driver.
  
  Status
  ------
  It only support basic block read/write functions in the NVMe driver.
  
  Config options
  --------------
  CONFIG_NVME	Enable NVMe device support
  CONFIG_CMD_NVME	Enable basic NVMe commands
  
  Usage in U-Boot
  ---------------
  To use an NVMe hard disk from U-Boot shell, a 'nvme scan' command needs to
  be executed for all NVMe hard disks attached to the NVMe controller to be
  identified.
  
  To list all of the NVMe hard disks, try:
  
    => nvme info
    Device 0: Vendor: 0x8086 Rev: 8DV10131 Prod: CVFT535600LS400BGN
  	    Type: Hard Disk
  	    Capacity: 381554.0 MB = 372.6 GB (781422768 x 512)
  
  and print out detailed information for controller and namespaces via:
  
    => nvme detail
  
  Raw block read/write to can be done via the 'nvme read/write' commands:
  
    => nvme read a0000000 0 11000
  
    => tftp 80000000 /tftpboot/kernel.itb
    => nvme write 80000000 0 11000
  
  Of course, file system command can be used on the NVMe hard disk as well:
  
    => fatls nvme 0:1
  	32376967   kernel.itb
  	22929408   100m
  
  	2 file(s), 0 dir(s)
  
    => fatload nvme 0:1 a0000000 /kernel.itb
    => bootm a0000000
  
  Testing NVMe with QEMU x86
  --------------------------
  QEMU supports NVMe emulation and we can test NVMe driver with QEMU x86 running
  U-Boot. Please see README.x86 for how to build u-boot.rom image for QEMU x86.
  
  Example command line to call QEMU x86 below with emulated NVMe device:
  $ ./qemu-system-i386 -drive file=nvme.img,if=none,id=drv0 -device nvme,drive=drv0,serial=QEMUNVME0001 -bios u-boot.rom