[RFC PATCH 00/15] Unify SPI delays into an `struct spi_delay`

[Alexandru Ardelean <alexandru.ardelean@xxxxxxxxxx>]

Initially, I started this patchset thinking: "we need a new delay for
something-something" (in case someone is curios, we need a CS-hold-time for
the first transfer, because the CS wakes a chip from sleep-mode).

Then I added the delay, and felt a bit dirty-inside about adding a new one
(just like that), and decided to look at maybe cleaning things up a bit,
and a few days later, I got here.

Full disclaimer: this patchset is not complete. It's an RFC.
It's based on top of Jonathan's `iio/togreg` branch which also includes the
ADIS driver library changes and also includes `cs_change_delay`.

I'll send a V2 patchset, which just the first 4 patches, since I feel that
those are a bit more complete.

I thought about just sending the first 4 patches on-their-own, but I
figured that the whole series (even if not complete) serves as a better
explanation about the whole "why?".

Hopefully, this can sort-of-explain things.
I'll reference this RFC on the next series.

Thanks

Alexandru Ardelean (15):
  spi: move `cs_change_delay` backwards compat logic outside switch
  spi: introduce spi_delay struct as "value + unit" &  spi_delay_exec()
  spi: make `cs_change_delay` the first user of the `spi_delay` logic
  iio: imu: adis: convert cs_change_delay to spi_delay struct
  spi: sprd: convert transfer word delay to spi_delay struct
  spi: orion: use new `word_delay` field for SPI transfers
  spi: spidev: use new `word_delay` field for spi transfers
  spi: core,atmel: convert `word_delay_usecs` -> `word_delay` for
    spi_device
  spi: introduce `delay` field for `spi_transfer` + spi_transfer_exec()
  spi: use new `spi_transfer_delay` helper where straightforward
  spi: tegra114: use `spi_transfer_delay` helper
  spi: spi-loopback-test: use new `delay` field
  spi: spidev: use new `delay` field for spi transfers
  spi: tegra114: change format for `spi_set_cs_timing()` function
  spi: implement SW control for CS times

 drivers/iio/imu/adis.c           |  24 ++---
 drivers/spi/spi-atmel.c          |  29 +++++-
 drivers/spi/spi-bcm63xx-hsspi.c  |   3 +-
 drivers/spi/spi-cavium.c         |   3 +-
 drivers/spi/spi-fsl-dspi.c       |   3 +-
 drivers/spi/spi-fsl-espi.c       |   3 +-
 drivers/spi/spi-fsl-spi.c        |   3 +-
 drivers/spi/spi-loopback-test.c  |  12 ++-
 drivers/spi/spi-mpc512x-psc.c    |   3 +-
 drivers/spi/spi-mpc52xx-psc.c    |   3 +-
 drivers/spi/spi-omap-100k.c      |   3 +-
 drivers/spi/spi-orion.c          |   6 +-
 drivers/spi/spi-pl022.c          |  25 +++--
 drivers/spi/spi-sc18is602.c      |   3 +-
 drivers/spi/spi-sh-hspi.c        |   3 +-
 drivers/spi/spi-sprd.c           |  11 ++-
 drivers/spi/spi-tegra114.c       |  39 +++++---
 drivers/spi/spi-tegra20-sflash.c |   2 +-
 drivers/spi/spi-topcliff-pch.c   |   7 +-
 drivers/spi/spi-txx9.c           |   3 +-
 drivers/spi/spi-xcomm.c          |   3 +-
 drivers/spi/spi.c                | 162 +++++++++++++++++++++++++------
 drivers/spi/spidev.c             |   6 +-
 include/linux/spi/spi.h          |  65 ++++++++++---
 24 files changed, 293 insertions(+), 131 deletions(-)

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2.20.1