1. 根目录:
2. drivers
3. mfd
4. atmel-flexcom.c

/*
 * Driver for Atmel Flexcom
 *
 * Copyright (C) 2015 Atmel Corporation
 *
 * Author: Cyrille Pitchen <cyrille.pitchen@atmel.com>
 *
 * 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>
#include <dt-bindings/mfd/atmel-flexcom.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_OFFSET	(0)  /* Operating Mode */
#define FLEX_MR_OPMODE_MASK	(0x3 << FLEX_MR_OPMODE_OFFSET)
#define FLEX_MR_OPMODE(opmode)	(((opmode) << FLEX_MR_OPMODE_OFFSET) &	\
				 FLEX_MR_OPMODE_MASK)


static int atmel_flexcom_probe(struct platform_device *pdev)
{
	struct device_node *np = pdev->dev.of_node;
	struct clk *clk;
	struct resource *res;
	void __iomem *base;
	u32 opmode;
	int err;

	err = of_property_read_u32(np, "atmel,flexcom-mode", &opmode);
	if (err)
		return err;

	if (opmode < ATMEL_FLEXCOM_MODE_USART ||
	    opmode > ATMEL_FLEXCOM_MODE_TWI)
		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(FLEX_MR_OPMODE(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 <cyrille.pitchen@atmel.com>");
MODULE_DESCRIPTION("Atmel Flexcom MFD driver");
MODULE_LICENSE("GPL v2");