drivers/rtc/rtc-m41t94.c

Source file repositories/reference/linux-study-clean/drivers/rtc/rtc-m41t94.c

File Facts

System
Linux kernel
Corpus path
drivers/rtc/rtc-m41t94.c
Extension
.c
Size
3763 bytes
Lines
146
Domain
Driver Families
Bucket
drivers/rtc
Inferred role
Driver Families: implementation source
Status
source implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Driver for ST M41T94 SPI RTC
 *
 * Copyright (C) 2008 Kim B. Heino
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/platform_device.h>
#include <linux/rtc.h>
#include <linux/spi/spi.h>
#include <linux/bcd.h>

#define M41T94_REG_SECONDS	0x01
#define M41T94_REG_MINUTES	0x02
#define M41T94_REG_HOURS	0x03
#define M41T94_REG_WDAY		0x04
#define M41T94_REG_DAY		0x05
#define M41T94_REG_MONTH	0x06
#define M41T94_REG_YEAR		0x07
#define M41T94_REG_HT		0x0c

#define M41T94_BIT_HALT		0x40
#define M41T94_BIT_STOP		0x80
#define M41T94_BIT_CB		0x40
#define M41T94_BIT_CEB		0x80

static int m41t94_set_time(struct device *dev, struct rtc_time *tm)
{
	struct spi_device *spi = to_spi_device(dev);
	u8 buf[8]; /* write cmd + 7 registers */

	dev_dbg(dev, "%s secs=%d, mins=%d, "
		"hours=%d, mday=%d, mon=%d, year=%d, wday=%d\n",
		"write", tm->tm_sec, tm->tm_min,
		tm->tm_hour, tm->tm_mday,
		tm->tm_mon, tm->tm_year, tm->tm_wday);

	buf[0] = 0x80 | M41T94_REG_SECONDS; /* write time + date */
	buf[M41T94_REG_SECONDS] = bin2bcd(tm->tm_sec);
	buf[M41T94_REG_MINUTES] = bin2bcd(tm->tm_min);
	buf[M41T94_REG_HOURS]   = bin2bcd(tm->tm_hour);
	buf[M41T94_REG_WDAY]    = bin2bcd(tm->tm_wday + 1);
	buf[M41T94_REG_DAY]     = bin2bcd(tm->tm_mday);
	buf[M41T94_REG_MONTH]   = bin2bcd(tm->tm_mon + 1);

	buf[M41T94_REG_HOURS] |= M41T94_BIT_CEB;
	if (tm->tm_year >= 100)
		buf[M41T94_REG_HOURS] |= M41T94_BIT_CB;
	buf[M41T94_REG_YEAR] = bin2bcd(tm->tm_year % 100);

	return spi_write(spi, buf, 8);
}

static int m41t94_read_time(struct device *dev, struct rtc_time *tm)
{
	struct spi_device *spi = to_spi_device(dev);
	u8 buf[2];
	int ret, hour;

	/* clear halt update bit */
	ret = spi_w8r8(spi, M41T94_REG_HT);
	if (ret < 0)
		return ret;
	if (ret & M41T94_BIT_HALT) {
		buf[0] = 0x80 | M41T94_REG_HT;
		buf[1] = ret & ~M41T94_BIT_HALT;
		spi_write(spi, buf, 2);
	}

	/* clear stop bit */
	ret = spi_w8r8(spi, M41T94_REG_SECONDS);
	if (ret < 0)
		return ret;
	if (ret & M41T94_BIT_STOP) {
		buf[0] = 0x80 | M41T94_REG_SECONDS;
		buf[1] = ret & ~M41T94_BIT_STOP;
		spi_write(spi, buf, 2);
	}

	tm->tm_sec  = bcd2bin(spi_w8r8(spi, M41T94_REG_SECONDS));
	tm->tm_min  = bcd2bin(spi_w8r8(spi, M41T94_REG_MINUTES));
	hour = spi_w8r8(spi, M41T94_REG_HOURS);
	tm->tm_hour = bcd2bin(hour & 0x3f);
	tm->tm_wday = bcd2bin(spi_w8r8(spi, M41T94_REG_WDAY)) - 1;
	tm->tm_mday = bcd2bin(spi_w8r8(spi, M41T94_REG_DAY));
	tm->tm_mon  = bcd2bin(spi_w8r8(spi, M41T94_REG_MONTH)) - 1;
	tm->tm_year = bcd2bin(spi_w8r8(spi, M41T94_REG_YEAR));
	if ((hour & M41T94_BIT_CB) || !(hour & M41T94_BIT_CEB))

Annotation

Implementation Notes