[RFC PATCH v2 0/5] MTD: Add Initial Hyperbus support

[Vignesh Raghavendra <vigneshr@ti.com>]

Cypress HyperBus is Low Signal Count, High Performance Double Data Rate Bus
interface between a host system master and one or more slave interfaces.
HyperBus is used to connect microprocessor, microcontroller, or ASIC
devices with random access NOR flash memory(called HyperFlash) or
self refresh DRAM(called HyperRAM).

Its a 8-bit data bus (DQ[7:0]) with  Read-Write Data Strobe (RWDS)
signal and either Single-ended clock(3.0V parts) or Differential clock
(1.8V parts). It uses ChipSelect lines to select b/w multiple slaves.
At bus level, it follows a separate protocol described in HyperBus
specification[1].

HyperFlash follows CFI AMD/Fujitsu Extended Command Set (0x0002) similar
to that of existing parallel NORs. Since Hyperbus is x8 DDR bus,
its equivalent to x16 parallel NOR flash wrt bits per clk. But Hyperbus
operates at >166MHz frequencies.
HyperRAM provides direct random read/write access to flash memory
array.
Framework is modelled along the lines of spi-nor framework. HyperBus
memory controller(HBMC) drivers call hyperbus_register_device() to register a
single HyperFlash device. HyperFlash core parses MMIO access
information from DT, sets up the map_info struct, probes CFI flash and
registers it with MTD framework.

This is an early RFC, to know if its okay to use maps framework and existing
CFI compliant flash support code to support Hyperflash
Also would like input on different types of HBMC master IPs out there
and their programming sequences.
Would appreciate any testing/review.

Tested on modified TI AM654 EVM with Cypress Hyperflash S26KS512 by
creating a UBIFS partition and writing and reading files to it.
Stress tested by writing/reading 16MB flash repeatedly at different
offsets using dd commmand.

HyperBus specification can be found at[1]
HyperFlash datasheet can be found at[2]
TI's HBMC controller details at[3]

[1] https://www.cypress.com/file/213356/download
[2] https://www.cypress.com/file/213346/download
[3] http://www.ti.com/lit/ug/spruid7b/spruid7b.pdf
    Table 12-5741. HyperFlash Access Sequence
Enumeration log:
https://pastebin.ubuntu.com/p/GhqxJ8XTTx/

Change log:
Since RFC v1:
* Re-work Hyperbus core to provide separate struct representation for
  controller and slave devices
* Rename all files and func names to have hyperbus_ prefix
* Provide default calibration routine for use by controller drivers
* Fix up errors with patch spliting
* Address comments by Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>


Vignesh Raghavendra (5):
  mtd: cfi_cmdset_0002: Add support for polling status register
  dt-bindings: mtd: Add binding documentation for Hyperbus memory
    devices
  mtd: Add support for Hyperbus memory devices
  dt-bindings: mtd: Add bindings for TI's AM654 Hyperbus memory
    controller
  mtd: hyperbus: Add driver for TI's Hyperbus memory controller

 .../bindings/mtd/cypress,hyperbus.txt         |   6 +
 .../devicetree/bindings/mtd/ti,am654-hbmc.txt |  27 +++
 MAINTAINERS                                   |   8 +
 drivers/mtd/Kconfig                           |   2 +
 drivers/mtd/Makefile                          |   1 +
 drivers/mtd/chips/cfi_cmdset_0002.c           |  50 +++++
 drivers/mtd/hyperbus/Kconfig                  |  21 ++
 drivers/mtd/hyperbus/Makefile                 |   4 +
 drivers/mtd/hyperbus/hbmc_am654.c             | 108 +++++++++++
 drivers/mtd/hyperbus/hyperbus-core.c          | 183 ++++++++++++++++++
 include/linux/mtd/cfi.h                       |   5 +
 include/linux/mtd/hyperbus.h                  |  91 +++++++++
 12 files changed, 506 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/mtd/cypress,hyperbus.txt
 create mode 100644 Documentation/devicetree/bindings/mtd/ti,am654-hbmc.txt
 create mode 100644 drivers/mtd/hyperbus/Kconfig
 create mode 100644 drivers/mtd/hyperbus/Makefile
 create mode 100644 drivers/mtd/hyperbus/hbmc_am654.c
 create mode 100644 drivers/mtd/hyperbus/hyperbus-core.c
 create mode 100644 include/linux/mtd/hyperbus.h

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2.21.0