Merge branch '2023-04-27-introduce-nvm-xip-block-storage-emulation'

To quote the author:
Adding block storage emulation for NVM XIP flash devices.

Some paltforms such as Corstone-1000 need to see NVM XIP raw flash
as a block storage device with read only capability.

Here NVM flash devices are devices with addressable
memory (e.g: QSPI NOR flash).

The NVM XIP block storage emulation provides the following features:

- Emulate NVM XIP raw flash as a block storage device with read only capability
- Being generic by design and can be used by any platform
- Device tree node
- Platforms can use multiple NVM XIP devices at the same time by defining a
  DT node for each one of them
- A generic NVMXIP block driver allowing to read from the XIP flash
- A generic NVMXIP Uclass driver for binding the block device
- A generic NVMXIP QSPI driver
- Implemented on top of memory-mapped IO (using readq macro)
- Enabling NVMXIP in sandbox64
- A sandbox test case
- Enabling NVMXIP in Corstone1000 platform as a use case

For more details please refer to doc/develop/driver-model/nvmxip.rst

2 files changed, 92 insertions, 0 deletions

diff --git a/doc/develop/driver-model/index.rst b/doc/develop/driver-model/index.rst
index 7366ef818c5..8e12bbd9366 100644
--- a/doc/develop/driver-model/index.rst
+++ b/doc/develop/driver-model/index.rst
@@ -20,6 +20,7 @@ subsystems
    livetree
    migration
    nvme
+   nvmxip
    of-plat
    pci-info
    pmic-framework
diff --git a/doc/develop/driver-model/nvmxip.rst b/doc/develop/driver-model/nvmxip.rst
new file mode 100644
index 00000000000..e85dc220b9c
--- /dev/null
+++ b/doc/develop/driver-model/nvmxip.rst
@@ -0,0 +1,91 @@
+.. SPDX-License-Identifier: GPL-2.0+
+
+NVM XIP Block Storage Emulation Driver
+=======================================
+
+Summary
+-------
+
+Non-Volatile Memory devices with addressable memory (e.g: QSPI NOR flash) could
+be used for block storage needs (e.g: parsing a GPT layout in a raw QSPI NOR flash).
+
+The NVMXIP Uclass provides this functionality and can be used for any 64-bit platform.
+
+The NVMXIP Uclass provides the following drivers:
+
+      nvmxip-blk block driver:
+
+        A generic block driver allowing to read from the XIP flash.
+	The driver belongs to UCLASS_BLK.
+	The driver implemented by drivers/mtd/nvmxip/nvmxip.c
+
+      nvmxip Uclass driver:
+
+        When a device is described in the DT and associated with UCLASS_NVMXIP,
+        the Uclass creates a block device and binds it with the nvmxip-blk.
+	The Uclass driver implemented by drivers/mtd/nvmxip/nvmxip-uclass.c
+
+      nvmxip_qspi driver :
+
+        The driver probed with the DT and is the parent of the blk#<id> device.
+        nvmxip_qspi can be reused by other platforms. If the platform
+        has custom settings to apply before using the flash, then the platform
+        can provide its own parent driver belonging to UCLASS_NVMXIP and reuse
+        nvmxip-blk. The custom driver can be implemented like nvmxip_qspi in
+        addition to the platform custom settings.
+	The nvmxip_qspi driver belongs to UCLASS_NVMXIP.
+	The driver implemented by drivers/mtd/nvmxip/nvmxip_qspi.c
+
+	For example, if we have two NVMXIP devices described in the DT
+	The devices hierarchy is as follows:
+
+::
+
+   => dm tree
+
+        Class     Index  Probed  Driver                Name
+    -----------------------------------------------------------
+    ...
+     nvmxip        0  [ + ]   nvmxip_qspi           |-- nvmxip-qspi1@08000000
+     blk           3  [ + ]   nvmxip-blk                    |   `-- [email protected]#1
+     nvmxip        1  [ + ]   nvmxip_qspi           |-- nvmxip-qspi2@08200000
+     blk           4  [ + ]   nvmxip-blk                    |   `-- [email protected]#2
+
+The implementation is generic and can be used by different platforms.
+
+Supported hardware
+--------------------------------
+
+Any plaform supporting readq().
+
+Configuration
+----------------------
+
+config NVMXIP
+	  This option allows the emulation of a block storage device
+	  on top of a direct access non volatile memory XIP flash devices.
+	  This support provides the read operation.
+	  This option provides the block storage driver nvmxip-blk which
+	  handles the read operation. This driver is HW agnostic and can support
+	  multiple flash devices at the same time.
+
+config NVMXIP_QSPI
+	  This option allows the emulation of a block storage device on top of a QSPI XIP flash.
+	  Any platform that needs to emulate one or multiple QSPI XIP flash devices can turn this
+	  option on to enable the functionality. NVMXIP config is selected automatically.
+	  Platforms that need to add custom treatments before accessing to the flash, can
+	  write their own driver (same as nvmxip_qspi in addition to the custom settings).
+
+Device Tree nodes
+--------------------
+
+Multiple QSPI XIP flash devices can be used at the same time by describing them through DT
+nodes.
+
+Please refer to the documentation of the DT binding at:
+
+doc/device-tree-bindings/nvmxip/nvmxip_qspi.txt
+
+Contributors
+------------
+   * Abdellatif El Khlifi <[email protected]>