linux-kernel - Re: [PATCH v3 4/6] spi: spi-axi-spi-engine: Add support for MOSI idle configuration

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Date: Wed, 5 Jun 2024 12:03:38 -0500
From: David Lechner <dlechner@...libre.com>
To: Marcelo Schmitt <marcelo.schmitt@...log.com>, broonie@...nel.org,
 lars@...afoo.de, Michael.Hennerich@...log.com, jic23@...nel.org,
 robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
 nuno.sa@...log.com, marcelo.schmitt1@...il.com
Cc: linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
 linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 4/6] spi: spi-axi-spi-engine: Add support for MOSI idle
 configuration

On 6/4/24 5:43 PM, Marcelo Schmitt wrote:
> Implement MOSI idle low and MOSI idle high to better support peripherals
> that request specific MOSI behavior.
> 
> Signed-off-by: Marcelo Schmitt <marcelo.schmitt@...log.com>
> ---
>  drivers/spi/spi-axi-spi-engine.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/spi/spi-axi-spi-engine.c b/drivers/spi/spi-axi-spi-engine.c
> index 0aa31d745734..549f03069d0e 100644
> --- a/drivers/spi/spi-axi-spi-engine.c
> +++ b/drivers/spi/spi-axi-spi-engine.c
> @@ -41,6 +41,7 @@
>  #define SPI_ENGINE_CONFIG_CPHA			BIT(0)
>  #define SPI_ENGINE_CONFIG_CPOL			BIT(1)
>  #define SPI_ENGINE_CONFIG_3WIRE			BIT(2)
> +#define SPI_ENGINE_CONFIG_SDO_IDLE		BIT(3)
>  
>  #define SPI_ENGINE_INST_TRANSFER		0x0
>  #define SPI_ENGINE_INST_ASSERT			0x1
> @@ -132,6 +133,10 @@ static unsigned int spi_engine_get_config(struct spi_device *spi)
>  		config |= SPI_ENGINE_CONFIG_CPHA;
>  	if (spi->mode & SPI_3WIRE)
>  		config |= SPI_ENGINE_CONFIG_3WIRE;
> +	if (spi->mode & SPI_MOSI_IDLE_HIGH)
> +		config |= SPI_ENGINE_CONFIG_SDO_IDLE;
> +	if (spi->mode & SPI_MOSI_IDLE_LOW)
> +		config &= ~SPI_ENGINE_CONFIG_SDO_IDLE;
>  
>  	return config;
>  }
> @@ -645,7 +650,8 @@ static int spi_engine_probe(struct platform_device *pdev)
>  		return ret;
>  
>  	host->dev.of_node = pdev->dev.of_node;
> -	host->mode_bits = SPI_CPOL | SPI_CPHA | SPI_3WIRE;
> +	host->mode_bits = SPI_CPOL | SPI_CPHA | SPI_3WIRE | SPI_MOSI_IDLE_LOW
> +			  | SPI_MOSI_IDLE_HIGH;
>  	host->bits_per_word_mask = SPI_BPW_RANGE_MASK(1, 32);
>  	host->max_speed_hz = clk_get_rate(spi_engine->ref_clk) / 2;
>  	host->transfer_one_message = spi_engine_transfer_one_message;

I think we need a version check instead of setting the flags unconditionally
here since older versions of the AXI SPI Engine won't support this feature.