[v2] spi: mt7621: allow GPIO chip select lines

Extract a magic number, from mt7621_spi_probe(), used to
declare the number of chip select lines (which co-incides
with the native chip select count of 2) to a macro.

Use the newly defined MT7621_NATIVE_CS_COUNT macro to
instead populate both the spi_controller's max_native_cs
and num_chipselect members.

Declare that the spi_controller should use_gpio_descriptors
if present in the device properties (such as those declared
in the cs-gpio property of a "ralink,mt7621-spi" compatible
device-tree node) so that the SPI core will recalculcate
num_chipselect to account for the GPIO descriptors that
it should have populated in the cs_gpiod array member.

Remove the assignment of mt7621_spi_transfer_one_message()
to the spi_controller's transfer_one_message hook.

Refactor the mt7621_spi_transfer_one_message() logic into
mt7621_spi_prepare_message() and mt7621_spi_transfer_one()
and assign both to the spi_controller's prepare_message
and transfer_one hooks respectively.

Migrate the call mt7621_spi_transfer_one_message() made to
mt7621_spi_flush() just before chip select deactivation,
to the end of mt7621_spi_write_half_duplex() to ensure
that any pending data is shifted out of MOSI before the SPI
core deactivates the chip select line.

As chip select activation is now taken care of by the SPI
core, due to the use of the transfer_one hook instead of
transfer_one_message, the calls to mt7621_spi_set_cs()
from mt7621_spi_transfer_one_message() have fallen away.

And although the SPI core will handle activation for GPIO
chip select lines behind the scenes, it requires a callback
to allow the driver to perform controller-specific
operations to control its native chip select lines.

Rename mt7621_spi_set_cs() to mt7621_spi_set_native_cs()
and make sure that it takes into account the activation
polarity of the chip select line it's acting upon, as the
passed enable parameter represents the desired line level
and not the desired activation state, and then assign
mt7621_set_cs() to the spi_controller's set_cs hook.

Signed-off-by: Justin Swartz <justin.swartz@risingedge.co.za>
---

Changes from v1 to v2:

  Mark Brown recommended using the transfer_one hook
  approach, so I did.


 drivers/spi/spi-mt7621.c | 95 +++++++++++++++++++---------------------
 1 file changed, 45 insertions(+), 50 deletions(-)

--

On 2024-03-18 12:16, AngeloGioacchino Del Regno wrote:
> Il 16/03/24 02:03, Justin Swartz ha scritto:
>> Extract a magic number, from mt7621_spi_probe(), used to
>> declare the number of chip select lines (which co-incides
>> with the native chip select count of 2) to a macro.
>> 
>> Use the newly defined MT7621_NATIVE_CS_COUNT macro to
>> instead populate both the spi_controller's max_native_cs
>> and num_chipselect members.
>> 
>> Declare that the spi_controller should use_gpio_descriptors
>> if present in the device properties (such as those declared
>> in the cs-gpio property of a "ralink,mt7621-spi" compatible
>> device-tree node) so that the SPI core will recalculcate
>> num_chipselect to account for the GPIO descriptors that
>> it should have populated in the cs_gpiod array member.
>> 
>> Remove the assignment of mt7621_spi_transfer_one_message()
>> to the spi_controller's transfer_one_message hook.
>> 
>> Refactor the mt7621_spi_transfer_one_message() logic into
>> mt7621_spi_prepare_message() and mt7621_spi_transfer_one()
>> and assign both to the spi_controller's prepare_message
>> and transfer_one hooks respectively.
>> 
>> Migrate the call mt7621_spi_transfer_one_message() made to
>> mt7621_spi_flush() just before chip select deactivation,
>> to the end of mt7621_spi_write_half_duplex() to ensure
>> that any pending data is shifted out of MOSI before the SPI
>> core deactivates the chip select line.
>> 
>> As chip select activation is now taken care of by the SPI
>> core, due to the use of the transfer_one hook instead of
>> transfer_one_message, the calls to mt7621_spi_set_cs()
>> from mt7621_spi_transfer_one_message() have fallen away.
>> 
>> And although the SPI core will handle activation for GPIO
>> chip select lines behind the scenes, it requires a callback
>> to allow the driver to perform controller-specific
>> operations to control its native chip select lines.
>> 
>> Rename mt7621_spi_set_cs() to mt7621_spi_set_native_cs()
>> and make sure that it takes into account the activation
>> polarity of the chip select line it's acting upon, as the
>> passed enable parameter represents the desired line level
>> and not the desired activation state, and then assign
>> mt7621_set_cs() to the spi_controller's set_cs hook.
>> 
>> Signed-off-by: Justin Swartz <justin.swartz@risingedge.co.za>
> 
> Reviewed-by: AngeloGioacchino Del Regno
> <angelogioacchino.delregno@collabora.com>

Thank you very much for the review.

On Sat, 16 Mar 2024 03:03:01 +0200, Justin Swartz wrote:
> Extract a magic number, from mt7621_spi_probe(), used to
> declare the number of chip select lines (which co-incides
> with the native chip select count of 2) to a macro.
> 
> Use the newly defined MT7621_NATIVE_CS_COUNT macro to
> instead populate both the spi_controller's max_native_cs
> and num_chipselect members.
> 
> [...]

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git for-next

Thanks!

[1/1] spi: mt7621: allow GPIO chip select lines
      commit: 2a741cd6ec5899cec054ae27120f490ad57bc6bb

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark