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Date:   Mon, 18 Mar 2019 07:43:47 +0000
From:   Rasmus Villemoes <Rasmus.Villemoes@...vas.se>
To:     Mark Brown <broonie@...nel.org>, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>
CC:     Esben Haabendal <esben@...nix.com>,
        Fabio Estevam <festevam@...il.com>,
        Per Christensen <pnc@...f.com>,
        "linux-spi@...r.kernel.org" <linux-spi@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] spi: spi-fsl-spi: support use of the SPISEL_BOOT signal
 on MPC8309

ping

On 06/03/2019 11.32, Rasmus Villemoes wrote:
> The MPC8309 has a dedicated signal, SPISEL_BOOT, usually used as chip
> select for the flash device from which the bootloader is loaded. It is
> not an ordinary gpio, but is simply controlled via the SPI_CS register
> in the system configuration.
> 
> To allow accessing such a spi slave, we need to teach
> fsl_spi_cs_control() how to control the SPISEL_BOOT signal. To
> distinguish the gpio-controlled slaves, continue to have those use
> chip_select values of 0..ngpios-1, and use chip_select == ngpios for
> the boot flash.
> 
> I'm not too happy with all the ifdeffery, but it seems to be necessary
> for guarding the sysdev/fsl_soc.h and use of
> get_immrbase() (spi-fsl-lib.c already contains similar ifdeffery).
> 
> Googling suggests that the MPC8306 is similar, with the SPI_CS
> register at the same offset.
> 
> Signed-off-by: Rasmus Villemoes <rasmus.villemoes@...vas.dk>
> ---
>  .../devicetree/bindings/spi/fsl-spi.txt       |  4 ++
>  drivers/spi/spi-fsl-lib.h                     |  2 +
>  drivers/spi/spi-fsl-spi.c                     | 40 ++++++++++++++++---
>  3 files changed, 41 insertions(+), 5 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/spi/fsl-spi.txt b/Documentation/devicetree/bindings/spi/fsl-spi.txt
> index 8854004a1d3a..411375eac54d 100644
> --- a/Documentation/devicetree/bindings/spi/fsl-spi.txt
> +++ b/Documentation/devicetree/bindings/spi/fsl-spi.txt
> @@ -18,6 +18,10 @@ Optional properties:
>  - gpios : specifies the gpio pins to be used for chipselects.
>    The gpios will be referred to as reg = <index> in the SPI child nodes.
>    If unspecified, a single SPI device without a chip select can be used.
> +- fsl,spisel_boot : for the MPC8306 and MPC8309, specifies that the
> +  SPISEL_BOOT signal is used as chip select for a slave device. Use
> +  reg = <number of gpios> in the corresponding child node, i.e. 0 if
> +  the gpios property is not present.
>  
>  Example:
>  	spi@4c0 {
> diff --git a/drivers/spi/spi-fsl-lib.h b/drivers/spi/spi-fsl-lib.h
> index f303f306b38e..483734bc1b1e 100644
> --- a/drivers/spi/spi-fsl-lib.h
> +++ b/drivers/spi/spi-fsl-lib.h
> @@ -95,8 +95,10 @@ static inline u32 mpc8xxx_spi_read_reg(__be32 __iomem *reg)
>  
>  struct mpc8xxx_spi_probe_info {
>  	struct fsl_spi_platform_data pdata;
> +	int ngpios;
>  	int *gpios;
>  	bool *alow_flags;
> +	__be32 __iomem *immr_spi_cs;
>  };
>  
>  extern u32 mpc8xxx_spi_tx_buf_u8(struct mpc8xxx_spi *mpc8xxx_spi);
> diff --git a/drivers/spi/spi-fsl-spi.c b/drivers/spi/spi-fsl-spi.c
> index 8f2e97857e8b..3d7b50c65f36 100644
> --- a/drivers/spi/spi-fsl-spi.c
> +++ b/drivers/spi/spi-fsl-spi.c
> @@ -39,6 +39,14 @@
>  #include <linux/spi/spi_bitbang.h>
>  #include <linux/types.h>
>  
> +#ifdef CONFIG_FSL_SOC
> +#include <sysdev/fsl_soc.h>
> +#endif
> +
> +/* Specific to the MPC8306/MPC8309 */
> +#define IMMR_SPI_CS_OFFSET 0x14c
> +#define SPI_BOOT_SEL_BIT   0x80000000
> +
>  #include "spi-fsl-lib.h"
>  #include "spi-fsl-cpm.h"
>  #include "spi-fsl-spi.h"
> @@ -701,10 +709,17 @@ static void fsl_spi_cs_control(struct spi_device *spi, bool on)
>  	struct fsl_spi_platform_data *pdata = dev_get_platdata(dev);
>  	struct mpc8xxx_spi_probe_info *pinfo = to_of_pinfo(pdata);
>  	u16 cs = spi->chip_select;
> -	int gpio = pinfo->gpios[cs];
> -	bool alow = pinfo->alow_flags[cs];
>  
> -	gpio_set_value(gpio, on ^ alow);
> +	if (cs < pinfo->ngpios) {
> +		int gpio = pinfo->gpios[cs];
> +		bool alow = pinfo->alow_flags[cs];
> +
> +		gpio_set_value(gpio, on ^ alow);
> +	} else {
> +		if (WARN_ON_ONCE(cs > pinfo->ngpios || !pinfo->immr_spi_cs))
> +			return;
> +		iowrite32be(on ? SPI_BOOT_SEL_BIT : 0, pinfo->immr_spi_cs);
> +	}
>  }
>  
>  static int of_fsl_spi_get_chipselects(struct device *dev)
> @@ -712,12 +727,15 @@ static int of_fsl_spi_get_chipselects(struct device *dev)
>  	struct device_node *np = dev->of_node;
>  	struct fsl_spi_platform_data *pdata = dev_get_platdata(dev);
>  	struct mpc8xxx_spi_probe_info *pinfo = to_of_pinfo(pdata);
> +	bool spisel_boot = IS_ENABLED(CONFIG_FSL_SOC) &&
> +		of_property_read_bool(np, "fsl,spisel_boot");
>  	int ngpios;
>  	int i = 0;
>  	int ret;
>  
>  	ngpios = of_gpio_count(np);
> -	if (ngpios <= 0) {
> +	ngpios = max(ngpios, 0);
> +	if (ngpios == 0 && !spisel_boot) {
>  		/*
>  		 * SPI w/o chip-select line. One SPI device is still permitted
>  		 * though.
> @@ -726,6 +744,7 @@ static int of_fsl_spi_get_chipselects(struct device *dev)
>  		return 0;
>  	}
>  
> +	pinfo->ngpios = ngpios;
>  	pinfo->gpios = kmalloc_array(ngpios, sizeof(*pinfo->gpios),
>  				     GFP_KERNEL);
>  	if (!pinfo->gpios)
> @@ -769,7 +788,18 @@ static int of_fsl_spi_get_chipselects(struct device *dev)
>  		}
>  	}
>  
> -	pdata->max_chipselect = ngpios;
> +#if IS_ENABLED(CONFIG_FSL_SOC)
> +	if (spisel_boot) {
> +		pinfo->immr_spi_cs = ioremap(get_immrbase() + IMMR_SPI_CS_OFFSET, 4);
> +		if (!pinfo->immr_spi_cs) {
> +			ret = -ENOMEM;
> +			i = ngpios - 1;
> +			goto err_loop;
> +		}
> +	}
> +#endif
> +
> +	pdata->max_chipselect = ngpios + spisel_boot;
>  	pdata->cs_control = fsl_spi_cs_control;
>  
>  	return 0;
> 

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