Subject: [PATCH v7 2/2] mfd: atmel-flexcom: add a driver for Atmel Flexible Serial Communication Unit

From: [email-masked] (Lee Jones)
Date: Fri, 24 Jul 2015 09:43:55 +0100

On Thu, 23 Jul 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, using the "reg" property of the first
> (should be unique) available DT child node.
> 
> 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.
> 
> 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 <[email-masked]>
> ---
>  drivers/mfd/Kconfig         |  11 +++++
>  drivers/mfd/Makefile        |   1 +
>  drivers/mfd/atmel-flexcom.c | 113 ++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 125 insertions(+)
>  create mode 100644 drivers/mfd/atmel-flexcom.c
> 
> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> index 653815950aa2..2c75472c679c 100644
> --- a/drivers/mfd/Kconfig
> +++ b/drivers/mfd/Kconfig
> @@ -60,6 +60,17 @@ 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.

Please grep for QCOM_GSBI in drivers/soc/qcom/*

Similar right?

Perhaps this should live in drivers/soc/atmel/* instead?

>  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 ea40e076cb61..0705eb2d873d 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 000000000000..0d06b70696b0
> --- /dev/null
> +++ b/drivers/mfd/atmel-flexcom.c
> @@ -0,0 +1,113 @@
> +/*
> + * Driver for Atmel Flexcom
> + *
> + * Copyright (C) 2015 Atmel Corporation
> + *
> + * Author: Cyrille Pitchen <[email-masked]>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + * You should have received a copy of the GNU General Public License along with
> + * this program.  If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#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>
> +
> +/* I/O register offsets */
> +#define FLEX_MR		0x0	/* Mode Register */
> +#define FLEX_VERSION	0xfc	/* Version Register */
> +
> +/* Mode Register bit fields */
> +#define FLEX_MR_OPMODE_MASK	0x3
> +#define FLEX_MR_OPMODE_NO_COM	0x0
> +#define FLEX_MR_OPMODE_USART	0x1
> +#define FLEX_MR_OPMODE_SPI	0x2
> +#define FLEX_MR_OPMODE_TWI	0x3
> +
> +
> +static int atmel_flexcom_probe(struct platform_device *pdev)
> +{
> +	struct device_node *child, *np = pdev->dev.of_node;
> +	struct clk *clk;
> +	struct resource *res;
> +	void __iomem *base;
> +	u32 opmode;
> +	int err;
> +
> +	child = of_get_next_available_child(np, NULL);
> +	if (!child)
> +		return -ENODEV;
> +
> +	/*
> +	 * The Operating Mode is stored into the first u32 of the reg property
> +	 * of the child.
> +	 */
> +	err = of_property_read_u32_index(child, "reg", 0, &opmode);
> +	of_node_put(child);

Don't think you need to of_node_put() after a u32 read.

> +	if (err)
> +		return -EINVAL;

Why are you making up your own return value.

Just return err.

> +	if ((opmode == FLEX_MR_OPMODE_NO_COM) ||
> +	    (opmode & ~FLEX_MR_OPMODE_MASK))
> +		return -EINVAL;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	base = devm_ioremap_resource(&pdev->dev, res);
> +	if (IS_ERR(base))
> +		return PTR_ERR(base);
> +
> +	clk = devm_clk_get(&pdev->dev, NULL);
> +	if (IS_ERR(clk))
> +		return PTR_ERR(clk);
> +
> +	err = clk_prepare_enable(clk);
> +	if (err)
> +		return err;
> +
> +	/*
> +	 * Set the Operating Mode in the Mode Register: only the selected device
> +	 * is clocked. Hence, registers of the other serial devices remain
> +	 * inaccessible and are read as zero. Also the external I/O lines of the
> +	 * Flexcom are muxed to reach the selected device.
> +	 */
> +	writel(opmode, base + FLEX_MR);
> +
> +	clk_disable_unprepare(clk);
> +
> +	return of_platform_populate(np, 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 = {
> +	.probe	= atmel_flexcom_probe,
> +	.driver	= {
> +		.name		= "atmel_flexcom",
> +		.of_match_table	= atmel_flexcom_of_match,
> +	},
> +};
> +
> +module_platform_driver(atmel_flexcom_driver);
> +
> +MODULE_AUTHOR("Cyrille Pitchen <[email-masked]>");
> +MODULE_DESCRIPTION("Atmel Flexcom MFD driver");
> +MODULE_LICENSE("GPL v2");

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