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