[PATCH v4 2/2] mfd: flexcom: add a driver for Atmel Flexible Serial Communication Unit

[Lee Jones]

On Mon, 22 Jun 2015, Cyrille Pitchen wrote:

> This driver supports the new Atmel Flexcom. The Flexcom is a wrapper which
> integrates one SPI controller, one I2C controller and one USART. Only one
> function can be enabled at a time. This driver selects the function once
> for all, when the Flexcom is probed, according to the value of the new
> "atmel,flexcom-mode" device tree property.
> 
> This driver has chosen to present the Flexcom to the system as a MFD so
> the implementation is seamless for the existing Atmel SPI, I2C and USART
> drivers.

No need for this driver.

Just create your 3 platform drivers and get them to read the mode at
probe time.  If the mode isn't the one pertaining to itself return
-ENODEV and the Device Driver API will attempt the probe the next
device.  Ensure all of the devices have the same compatible string
i.e. atmel,sama5d2-flexcom.

> Also the Flexcom embeds FIFOs: the latest patches of the SPI, I2C and
> USART drivers take advantage of this new feature.
> 
> Signed-off-by: Cyrille Pitchen <cyrille.pitchen at atmel.com>
> Acked-by: Boris Brezillon <boris.brezillon at free-electrons.com>
> Acked-by: Alexandre Belloni <alexandre.belloni at free-electrons.com>
> ---
>  drivers/mfd/Kconfig         | 11 +++++
>  drivers/mfd/Makefile        |  1 +
>  drivers/mfd/atmel-flexcom.c | 98 +++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 110 insertions(+)
>  create mode 100644 drivers/mfd/atmel-flexcom.c
> 
> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> index d5ad04d..9b33ad0 100644
> --- a/drivers/mfd/Kconfig
> +++ b/drivers/mfd/Kconfig
> @@ -59,6 +59,17 @@ config MFD_AAT2870_CORE
>  	  additional drivers must be enabled in order to use the
>  	  functionality of the device.
>  
> +config MFD_ATMEL_FLEXCOM
> +	tristate "Atmel Flexcom (Flexible Serial Communication Unit)"
> +	select MFD_CORE
> +	depends on OF
> +	help
> +	  Select this to get support for Atmel Flexcom. This is a wrapper
> +	  which embeds a SPI controller, a I2C controller and a USART. Only
> +	  one function can be used at a time. The choice is done at boot time
> +	  by the probe function of this MFD driver according to a device tree
> +	  property.
> +
>  config MFD_ATMEL_HLCDC
>  	tristate "Atmel HLCDC (High-end LCD Controller)"
>  	select MFD_CORE
> diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
> index 0e5cfeb..c666bf5 100644
> --- a/drivers/mfd/Makefile
> +++ b/drivers/mfd/Makefile
> @@ -160,6 +160,7 @@ obj-$(CONFIG_MFD_SPMI_PMIC)	+= qcom-spmi-pmic.o
>  obj-$(CONFIG_TPS65911_COMPARATOR)	+= tps65911-comparator.o
>  obj-$(CONFIG_MFD_TPS65090)	+= tps65090.o
>  obj-$(CONFIG_MFD_AAT2870_CORE)	+= aat2870-core.o
> +obj-$(CONFIG_MFD_ATMEL_FLEXCOM)	+= atmel-flexcom.o
>  obj-$(CONFIG_MFD_ATMEL_HLCDC)	+= atmel-hlcdc.o
>  obj-$(CONFIG_MFD_INTEL_MSIC)	+= intel_msic.o
>  obj-$(CONFIG_MFD_PALMAS)	+= palmas.o
> diff --git a/drivers/mfd/atmel-flexcom.c b/drivers/mfd/atmel-flexcom.c
> new file mode 100644
> index 0000000..7e7d4b8
> --- /dev/null
> +++ b/drivers/mfd/atmel-flexcom.c
> @@ -0,0 +1,98 @@
> +/*
> + * Driver for Atmel Flexcom
> + *
> + * Copyright (C) 2015 Atmel Corporation
> + *
> + * Author: Cyrille Pitchen <cyrille.pitchen at atmel.com>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + */
> +
> +#include <linux/module.h>
> +#include <linux/types.h>
> +#include <linux/kernel.h>
> +#include <linux/platform_device.h>
> +#include <linux/of.h>
> +#include <linux/of_platform.h>
> +#include <linux/err.h>
> +#include <linux/io.h>
> +#include <linux/clk.h>
> +
> +#define FX_MR		0x0
> +#define FX_RHR		0x10
> +#define FX_THR		0x20
> +#define FX_VERSION	0xfc
> +
> +#define FX_MR_NO_COM	0
> +#define FX_MR_USART	1
> +#define FX_MR_SPI	2
> +#define FX_MR_TWI	3
> +
> +
> +static int atmel_flexcom_probe(struct platform_device *pdev)
> +{
> +	struct clk *clk;
> +	struct resource *res;
> +	unsigned char __iomem *map;
> +	unsigned int version, mr;
> +	const char *mode;
> +	int err;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	map = devm_ioremap_resource(&pdev->dev, res);
> +	if (IS_ERR(map))
> +		return PTR_ERR(map);
> +
> +	clk = devm_clk_get(&pdev->dev, NULL);
> +	if (IS_ERR(clk))
> +		return PTR_ERR(clk);
> +
> +	err = of_property_read_string(pdev->dev.of_node,
> +				      "atmel,flexcom-mode", &mode);
> +	if (err)
> +		return err;
> +
> +	if (!strcmp(mode, "usart"))
> +		mr = FX_MR_USART;
> +	else if (!strcmp(mode, "spi"))
> +		mr = FX_MR_SPI;
> +	else if (!strcmp(mode, "twi") || !strcmp(mode, "i2c"))
> +		mr = FX_MR_TWI;
> +	else
> +		return -EINVAL;
> +
> +	err = clk_prepare_enable(clk);
> +	if (err)
> +		return err;
> +	version = readl(map + FX_VERSION);
> +	writel(mr, map + FX_MR);
> +	clk_disable_unprepare(clk);
> +
> +	dev_info(&pdev->dev, "version: %#x, mode: %s\n", version, mode);
> +
> +	return of_platform_populate(pdev->dev.of_node, NULL, NULL, &pdev->dev);
> +}
> +
> +static const struct of_device_id atmel_flexcom_of_match[] = {
> +	{ .compatible = "atmel,sama5d2-flexcom" },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, atmel_flexcom_of_match);
> +
> +static struct platform_driver atmel_flexcom_driver = {
> +	.driver		= {
> +		.name	= "atmel_flexcom",
> +		.of_match_table = atmel_flexcom_of_match,
> +	},
> +	.probe		= atmel_flexcom_probe,
> +};
> +
> +module_platform_driver(atmel_flexcom_driver);
> +
> +MODULE_AUTHOR("Cyrille Pitchen <cyrille.pitchen at atmel.com>");
> +MODULE_DESCRIPTION("Atmel Flexcom MFD driver");
> +MODULE_LICENSE("GPL");

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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