[PATCH v3 0/2] add support for Cadence's XSPI controller

[Parshuram Thombare]

This patch series adds support for Cadence's XSPI controller.
It supports 3 work modes.
1. ACMD (auto command) work mode
    ACMD name is because it uses auto command engine in the controller.
    It further has 2 modes PIO and CDMA (command DMA).
    The CDMA work mode is dedicated for high-performance application
    where very low software overhead is required. In this mode the
    Command Engine is programmed by the series of linked descriptors
    stored in system memory. These descriptors provide commands to execute
    and store status information for finished commands.
    The PIO mode work mode is dedicated for single operation where
    constructing a linked list of descriptors would require too
    much effort.
2. STIG (Software Triggered Instruction Generator) work mode
    In STIG mode, controller sends low-level instructions to memory.
    Each instruction is 128-bit width. There is special instruction
    DataSequence which carries information about data phase.
    Driver uses Slave DMA interface to transfer data as only this
    interface can be used in STIG work mode.
3. Direct work mode
    This work mode allows sending data without invoking any command through
    the slave interface.
Currently ACMD PIO mode is used for NOR flash read, program, erase
operations, all other operations are handled in STIG work mode.

Changes since v2:
1. Removed extra lock around exec_op.
2. Removed PHY parameters setting from the driver, those will be
   handled by bootstrap pins available in the controller.

Changes since v1:
1. Use ACMD PIO work mode for NOR read, program and erase operations,
   for everything else use STIG(Software Triggered Instruction
   Generator) work mode.
2. Changes suggested by Lukas.

Parshuram Thombare (2):
  spi: cadence: add dt-bindings documentation for Cadence XSPI
    controller
  spi: cadence: add support for Cadence XSPI controller

 .../devicetree/bindings/spi/cdns,xspi.yaml         |  66 ++
 drivers/spi/Kconfig                                |  11 +
 drivers/spi/Makefile                               |   1 +
 drivers/spi/spi-cadence-xspi.c                     | 837 +++++++++++++++++++++
 4 files changed, 915 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/spi/cdns,xspi.yaml
 create mode 100644 drivers/spi/spi-cadence-xspi.c

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2.7.4