The main goal of the short series is to provide a procedure implementing
the auto-detection of the number of native Chip-Select signals supported
by the controller. The suggested algorithm is straightforward. It relies
on the fact that the SER register writable flags reflects the actual
number of available native chip-select signals. So the DW APB/AHB SSI
driver now tests the SER register for having the writable bits,
calculates the number of CS signals based on the number of set flags and
then initializes the num_cs private data field based on that, which then
will be passed to the SPI-core subsystem indicating the number of
supported hardware chip-selects. The implemented procedure will be useful
for the DW SSI device nodes not having the explicitly set "num-cs"
property. In case if the property is specified it will be utilized instead
of the auto-detection procedure.

Besides of that a small cleanup patch is introduced in the head of the
series. It converts the driver to using the BITS_TO_BYTES() macro instead
of the hard-coded DIV_ROUND_UP()-based calculation of the number of
bytes-per-transfer-word.

Link: https://lore.kernel.org/linux-spi/20240215180102.13887-1-fancer.lancer@gmail.com
Changelog v2:
- Add a new patch:
  [PATCH v2 3/4] spi: dw: Convert dw_spi::num_cs to u32
- Fix some spelling notes (@Andy).

Link: https://lore.kernel.org/linux-spi/20240222172853.25082-1-fancer.lancer@gmail.com
Changelog v3:
- Add Andy' Rb tag.
- Rebase onto the kernel v6.9 and resubmit.

Link: https://lore.kernel.org/linux-spi/20240416155257.22429-1-fancer.lancer@gmail.com
Changelog v4:
- Just resend.

Signed-off-by: Serge Semin <fancer.lancer@gmail.com>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Andy Shevchenko <andy@kernel.org>
Cc: linux-spi@vger.kernel.org
Cc: linux-kernel@vger.kernel.org

Serge Semin (4):
  spi: dw: Convert to using BITS_TO_BYTES() macro
  spi: dw: Add a number of native CS auto-detection
  spi: dw: Convert dw_spi::num_cs to u32
  spi: dw: Drop default number of CS setting

 drivers/spi/spi-dw-core.c | 20 ++++++++++++++++----
 drivers/spi/spi-dw-mmio.c |  8 ++------
 drivers/spi/spi-dw.h      |  2 +-
 3 files changed, 19 insertions(+), 11 deletions(-)

-- 
2.43.0