Re: [PATCH v6 1/7] spi: Enable controllers to extend the SPI protocol with MOSI idle configuration

[David Lechner <dlechner@baylibre.com>]

On 6/29/24 2:04 PM, Marcelo Schmitt wrote:
> The behavior of an SPI controller data output line (SDO or MOSI or COPI
> (Controller Output Peripheral Input) for disambiguation) is usually not
> specified when the controller is not clocking out data on SCLK edges.
> However, there do exist SPI peripherals that require specific MOSI line
> state when data is not being clocked out of the controller.
> 
> Conventional SPI controllers may set the MOSI line on SCLK edges then bring
> it low when no data is going out or leave the line the state of the last
> transfer bit. More elaborated controllers are capable to set the MOSI idle
> state according to different configurable levels and thus are more suitable
> for interfacing with demanding peripherals.
> 
> Add SPI mode bits to allow peripherals to request explicit MOSI idle state
> when needed.
> 
> When supporting a particular MOSI idle configuration, the data output line
> state is expected to remain at the configured level when the controller is
> not clocking out data. When a device that needs a specific MOSI idle state
> is identified, its driver should request the MOSI idle configuration by
> setting the proper SPI mode bit.
> 
> Acked-by: Nuno Sa <nuno.sa@analog.com>
> Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
> ---

Tested both valid and invalid combinations of flags and saw expected
behavior/error messages in all cases.

Reviewed-by: David Lechner <dlechner@baylibre.com>
Tested-by: David Lechner <dlechner@baylibre.com>