linux-kernel - Re: [PATCH v4 4/6] spi: spi-axi-spi-engine: Add support for MOSI idle configuration

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Date: Wed, 19 Jun 2024 14:27:20 -0300
From: Marcelo Schmitt <marcelo.schmitt1@...il.com>
To: David Lechner <dlechner@...libre.com>
Cc: 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, linux-iio@...r.kernel.org,
	devicetree@...r.kernel.org, linux-spi@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 4/6] spi: spi-axi-spi-engine: Add support for MOSI
 idle configuration

On 06/19, David Lechner wrote:
> On 6/18/24 6:11 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, 8 insertions(+)
> > 
> > diff --git a/drivers/spi/spi-axi-spi-engine.c b/drivers/spi/spi-axi-spi-engine.c
> > index 0aa31d745734..787e22ae80c0 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)
> 
> Calling this SPI_ENGINE_CONFIG_SDO_IDLE_HIGH would make it more
> clear what happens when the bit is enabled.

Yeah, agreed. Changing to SPI_ENGINE_CONFIG_SDO_IDLE_HIGH.

> 
> >  
> >  #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;
> >  }
> > @@ -646,6 +651,9 @@ static int spi_engine_probe(struct platform_device *pdev)
> >  
> >  	host->dev.of_node = pdev->dev.of_node;
> >  	host->mode_bits = SPI_CPOL | SPI_CPHA | SPI_3WIRE;
> > +	if (ADI_AXI_PCORE_VER_MAJOR(version) >= 1 &&
> 
> Currently, the major version is required to be 1, so this check is not
> strictly needed.
> 
This is expecting the MOSI idle feature to be available on all versions from 1.3 on.
Will SPI-Engine always be major version 1?

> > +	    ADI_AXI_PCORE_VER_MINOR(version) >= 3)
> > +		host->mode_bits |=  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;
>