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91 lines
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.. SPDX-License-Identifier: GPL-2.0+
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NVM XIP Block Storage Emulation Driver
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======================================
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Summary
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-------
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Non-Volatile Memory devices with addressable memory (e.g: QSPI NOR flash) could
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be used for block storage needs (e.g: parsing a GPT layout in a raw QSPI NOR flash).
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The NVMXIP Uclass provides this functionality and can be used for any 64-bit platform.
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The NVMXIP Uclass provides the following drivers:
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nvmxip-blk block driver:
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A generic block driver allowing to read from the XIP flash.
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The driver belongs to UCLASS_BLK.
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The driver implemented by drivers/mtd/nvmxip/nvmxip.c
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nvmxip Uclass driver:
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When a device is described in the DT and associated with UCLASS_NVMXIP,
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the Uclass creates a block device and binds it with the nvmxip-blk.
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The Uclass driver implemented by drivers/mtd/nvmxip/nvmxip-uclass.c
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nvmxip_qspi driver :
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The driver probed with the DT and is the parent of the blk#<id> device.
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nvmxip_qspi can be reused by other platforms. If the platform
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has custom settings to apply before using the flash, then the platform
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can provide its own parent driver belonging to UCLASS_NVMXIP and reuse
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nvmxip-blk. The custom driver can be implemented like nvmxip_qspi in
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addition to the platform custom settings.
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The nvmxip_qspi driver belongs to UCLASS_NVMXIP.
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The driver implemented by drivers/mtd/nvmxip/nvmxip_qspi.c
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For example, if we have two NVMXIP devices described in the DT
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The devices hierarchy is as follows:
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::
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=> dm tree
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Class Index Probed Driver Name
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-----------------------------------------------------------
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...
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nvmxip 0 [ + ] nvmxip_qspi |-- nvmxip-qspi1@08000000
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blk 3 [ + ] nvmxip-blk | `-- nvmxip-qspi1@08000000.blk#1
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nvmxip 1 [ + ] nvmxip_qspi |-- nvmxip-qspi2@08200000
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blk 4 [ + ] nvmxip-blk | `-- nvmxip-qspi2@08200000.blk#2
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The implementation is generic and can be used by different platforms.
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Supported hardware
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------------------
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Any plaform supporting readq().
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Configuration
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-------------
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config NVMXIP
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This option allows the emulation of a block storage device
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on top of a direct access non volatile memory XIP flash devices.
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This support provides the read operation.
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This option provides the block storage driver nvmxip-blk which
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handles the read operation. This driver is HW agnostic and can support
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multiple flash devices at the same time.
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config NVMXIP_QSPI
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This option allows the emulation of a block storage device on top of a QSPI XIP flash.
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Any platform that needs to emulate one or multiple QSPI XIP flash devices can turn this
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option on to enable the functionality. NVMXIP config is selected automatically.
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Platforms that need to add custom treatments before accessing to the flash, can
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write their own driver (same as nvmxip_qspi in addition to the custom settings).
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Device Tree nodes
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-----------------
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Multiple QSPI XIP flash devices can be used at the same time by describing them through DT
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nodes.
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Please refer to the documentation of the DT binding at:
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doc/device-tree-bindings/nvmxip/nvmxip_qspi.txt
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Contributors
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------------
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* Abdellatif El Khlifi <abdellatif.elkhlifi@arm.com>
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