[RFC PATCH 0/2] spi: Add support for stacked/parallel memories

[Amit Kumar Mahapatra <amit.kumar-mahapatra@xxxxxxxxxx>]

This RFC is the continuation to the discussion which happened on
'commit f89504300e94 ("spi: Stacked/parallel memories bindings")' for
adding dtbinding support  for stacked/parallel memories.

The purpose of this patch series is to demonstrate the changes in spi-nor,
spi core and ZynqMP GQSPI driver w.r.t to stacked/parallel memories
support.Please go through the series and share you comments.

To support stacked/parallel configuration following changes are done to spi
core and spi-nor.

- The chip select member (chip_select) of the spi_device structure is changed
to an array (chip_select[2]). This array is used to store the CS values coming
form the "reg" DT property.

- Added a new member (cs_index_mask) in the spi_device structure to hold the
index information of above chip_select array. SPI-NOR is not aware of the
chip_select values, For any incoming request SPI-NOR will decide the flash
index with the help of individual flash size and the configuration type
(single/stacked/parallel). SPI-NOR will pass on the flash index information
to the SPI core by setting the appropriate bit(s) of "cs_index_mask".
For example if nth bit of "cs_index_mask" is set then the driver would
assert chip_slect[n].

- The flash parameter member(*params) of the spi_nor structure is changed
to an array (*params[2]). The array is used to store the parameters of each
flash connected in stacked/parallel configuration.

This patch series targets flashes of same make connected in stacked
configuration and for parallel configuration both the flashes should be
identical.
---
BRANCH: mtd/next
---
Amit Kumar Mahapatra (2):
  spi: Add multiple CS support for a single SPI device
  mtd: spi-nor: Add support for stacked/parallel memories

 drivers/mtd/spi-nor/core.c     | 104 +++++++++++++++++++++++++++++----
 drivers/mtd/spi-nor/core.h     |   5 ++
 drivers/spi/spi-zynqmp-gqspi.c |  30 ++++++++--
 drivers/spi/spi.c              |  10 +++-
 include/linux/mtd/spi-nor.h    |   8 ++-
 include/linux/spi/spi.h        |  10 +++-
 6 files changed, 146 insertions(+), 21 deletions(-)

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2.17.1