Subject: [PATCH v2 1/3] spi: atmel: add support for the internal chip-select of the spi controller

From: [email-masked] (Nicolas Ferre)
Date: Tue, 9 Jun 2015 10:07:00 +0200

Le 08/06/2015 18:07, Cyrille Pitchen a ?crit :
> This patch relies on the CSAAT (Chip Select Active After Transfer) feature
> introduced by the version 2 of the spi controller. This new mode allows to
> use properly the internal chip-select output pin of the spi controller
> instead of using external gpios. Consequently, the "cs-gpios" device-tree
> property becomes optional.
> 
> When the new CSAAT bit is set into the Chip Select Register, the internal
> chip-select output pin remains asserted till both the following conditions
> become true:
> - the LASTXFER bit is set into the Control Register (or the Transmit Data
>   Register)
> - the Transmit Data Register and its shift register are empty.
> 
> WARNING: if the LASTXFER bit is set into the Control Register then new
> data are written into the Transmit Data Register fast enough to keep its
> shifter not empty, the chip-select output pin remains asserted. Only when
> the shifter becomes empty, the chip-select output pin is unasserted.
> 
> When the CSAAT bit is clear in the Chip Select Register, the LASTXFER bit
> is ignored in both the Control Register and the Transmit Data Register.
> The internal chip-select output pin remains active as long as the Transmit
> Data Register or its shift register are not empty.
> 
> Signed-off-by: Cyrille Pitchen <[email-masked]>

It seems okay:
Acked-by: Nicolas Ferre <[email-masked]>

Thanks.

Some additional changes might be needed: see below...

> ---
>  drivers/spi/spi-atmel.c | 37 ++++++++++++++++++++++++++++---------
>  1 file changed, 28 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/spi/spi-atmel.c b/drivers/spi/spi-atmel.c
> index a2f40b1..aa7d202 100644
> --- a/drivers/spi/spi-atmel.c
> +++ b/drivers/spi/spi-atmel.c
> @@ -246,6 +246,7 @@ struct atmel_spi {
>  
>  	bool			use_dma;
>  	bool			use_pdc;
> +	bool			use_cs_gpios;
>  	/* dmaengine data */
>  	struct atmel_spi_dma	dma;
>  
> @@ -321,7 +322,8 @@ static void cs_activate(struct atmel_spi *as, struct spi_device *spi)
>  		}
>  
>  		mr = spi_readl(as, MR);
> -		gpio_set_value(asd->npcs_pin, active);
> +		if (as->use_cs_gpios)
> +			gpio_set_value(asd->npcs_pin, active);
>  	} else {
>  		u32 cpol = (spi->mode & SPI_CPOL) ? SPI_BIT(CPOL) : 0;
>  		int i;
> @@ -337,7 +339,7 @@ static void cs_activate(struct atmel_spi *as, struct spi_device *spi)
>  
>  		mr = spi_readl(as, MR);
>  		mr = SPI_BFINS(PCS, ~(1 << spi->chip_select), mr);
> -		if (spi->chip_select != 0)
> +		if (as->use_cs_gpios && spi->chip_select != 0)
>  			gpio_set_value(asd->npcs_pin, active);
>  		spi_writel(as, MR, mr);
>  	}

Maybe in a debug function in cs_activate()...

> @@ -366,7 +368,9 @@ static void cs_deactivate(struct atmel_spi *as, struct spi_device *spi)
>  			asd->npcs_pin, active ? " (low)" : "",
>  			mr);
>  
> -	if (atmel_spi_is_v2(as) || spi->chip_select != 0)
> +	if (!as->use_cs_gpios)
> +		spi_writel(as, CR, SPI_BIT(LASTXFER));
> +	else if (atmel_spi_is_v2(as) || spi->chip_select != 0)
>  		gpio_set_value(asd->npcs_pin, !active);
>  }
>  

... as well as in cs_deactivate(), you need to change the use of
asd->npcs_pin:

        dev_dbg(&spi->dev, "activate %u%s, mr %08x\n",
                        asd->npcs_pin, active ? " (high)" : "",
                        mr);

so that it is still relevant in the !as->use_cs_gpios case...

Bye,

> @@ -996,6 +1000,8 @@ static int atmel_spi_setup(struct spi_device *spi)
>  		csr |= SPI_BIT(CPOL);
>  	if (!(spi->mode & SPI_CPHA))
>  		csr |= SPI_BIT(NCPHA);
> +	if (!as->use_cs_gpios)
> +		csr |= SPI_BIT(CSAAT);
>  
>  	/* DLYBS is mostly irrelevant since we manage chipselect using GPIOs.
>  	 *
> @@ -1009,7 +1015,9 @@ static int atmel_spi_setup(struct spi_device *spi)
>  	/* chipselect must have been muxed as GPIO (e.g. in board setup) */
>  	npcs_pin = (unsigned long)spi->controller_data;
>  
> -	if (gpio_is_valid(spi->cs_gpio))
> +	if (!as->use_cs_gpios)
> +		npcs_pin = spi->chip_select;
> +	else if (gpio_is_valid(spi->cs_gpio))
>  		npcs_pin = spi->cs_gpio;
>  
>  	asd = spi->controller_state;
> @@ -1018,15 +1026,19 @@ static int atmel_spi_setup(struct spi_device *spi)
>  		if (!asd)
>  			return -ENOMEM;
>  
> -		ret = gpio_request(npcs_pin, dev_name(&spi->dev));
> -		if (ret) {
> -			kfree(asd);
> -			return ret;
> +		if (as->use_cs_gpios) {
> +			ret = gpio_request(npcs_pin, dev_name(&spi->dev));
> +			if (ret) {
> +				kfree(asd);
> +				return ret;
> +			}
> +
> +			gpio_direction_output(npcs_pin,
> +					      !(spi->mode & SPI_CS_HIGH));
>  		}
>  
>  		asd->npcs_pin = npcs_pin;
>  		spi->controller_state = asd;
> -		gpio_direction_output(npcs_pin, !(spi->mode & SPI_CS_HIGH));
>  	}
>  
>  	asd->csr = csr;
> @@ -1338,6 +1350,13 @@ static int atmel_spi_probe(struct platform_device *pdev)
>  
>  	atmel_get_caps(as);
>  
> +	as->use_cs_gpios = true;
> +	if (atmel_spi_is_v2(as) &&
> +	    !of_get_property(pdev->dev.of_node, "cs-gpios", NULL)) {
> +		as->use_cs_gpios = false;
> +		master->num_chipselect = 4;
> +	}
> +
>  	as->use_dma = false;
>  	as->use_pdc = false;
>  	if (as->caps.has_dma_support) {
> 

-- 
Nicolas Ferre