linux-imx

/*

 * SPI Driver for Microchip MCP795 RTC

 *

 * Copyright (C) Josef Gajdusek <atx@atx.name>

 *

 * based on other Linux RTC drivers

 *

 * Device datasheet:

 * http://ww1.microchip.com/downloads/en/DeviceDoc/22280A.pdf

 *

 * 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.

 *

 */

​

#include <linux/module.h>

#include <linux/kernel.h>

#include <linux/device.h>

#include <linux/printk.h>

#include <linux/spi/spi.h>

#include <linux/rtc.h>

#include <linux/of.h>

#include <linux/bcd.h>

#include <linux/delay.h>

​

/* MCP795 Instructions, see datasheet table 3-1 */

#define MCP795_EEREAD   0x03

#define MCP795_EEWRITE  0x02

#define MCP795_EEWRDI   0x04

#define MCP795_EEWREN   0x06

#define MCP795_SRREAD   0x05

#define MCP795_SRWRITE  0x01

#define MCP795_READ 0x13

#define MCP795_WRITE    0x12

#define MCP795_UNLOCK   0x14

#define MCP795_IDWRITE  0x32

#define MCP795_IDREAD   0x33

#define MCP795_CLRWDT   0x44

#define MCP795_CLRRAM   0x54

​

/* MCP795 RTCC registers, see datasheet table 4-1 */

#define MCP795_REG_SECONDS  0x01

#define MCP795_REG_DAY      0x04

#define MCP795_REG_MONTH    0x06

#define MCP795_REG_CONTROL  0x08

#define MCP795_REG_ALM0_SECONDS 0x0C

#define MCP795_REG_ALM0_DAY 0x0F

​

#define MCP795_ST_BIT       BIT(7)

#define MCP795_24_BIT       BIT(6)

#define MCP795_LP_BIT       BIT(5)

#define MCP795_EXTOSC_BIT   BIT(3)

#define MCP795_OSCON_BIT    BIT(5)

#define MCP795_ALM0_BIT     BIT(4)

#define MCP795_ALM1_BIT     BIT(5)

#define MCP795_ALM0IF_BIT   BIT(3)

#define MCP795_ALM0C0_BIT   BIT(4)

#define MCP795_ALM0C1_BIT   BIT(5)

#define MCP795_ALM0C2_BIT   BIT(6)

​

#define SEC_PER_DAY     (24 * 60 * 60)

​

static int mcp795_rtcc_read(struct device *dev, u8 addr, u8 *buf, u8 count)

{

    struct spi_device *spi = to_spi_device(dev);

    int ret;

    u8 tx[2];

​

    tx[0] = MCP795_READ;

    tx[1] = addr;

    ret = spi_write_then_read(spi, tx, sizeof(tx), buf, count);

​

    if (ret)

        dev_err(dev, "Failed reading %d bytes from address %x.\n",

                    count, addr);

​

    return ret;

}

​

static int mcp795_rtcc_write(struct device *dev, u8 addr, u8 *data, u8 count)

{

    struct spi_device *spi = to_spi_device(dev);

    int ret;

    u8 tx[257];

​

    tx[0] = MCP795_WRITE;

    tx[1] = addr;

    memcpy(&tx[2], data, count);

​

    ret = spi_write(spi, tx, 2 + count);

​