drivers/rtc/rtc-ds1216.c

Source file repositories/reference/linux-study-clean/drivers/rtc/rtc-ds1216.c

File Facts

System
Linux kernel
Corpus path
drivers/rtc/rtc-ds1216.c
Extension
.c
Size
3859 bytes
Lines
175
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

struct ds1216_regs {
	u8 tsec;
	u8 sec;
	u8 min;
	u8 hour;
	u8 wday;
	u8 mday;
	u8 month;
	u8 year;
};

#define DS1216_HOUR_1224	(1 << 7)
#define DS1216_HOUR_AMPM	(1 << 5)

struct ds1216_priv {
	struct rtc_device *rtc;
	void __iomem *ioaddr;
};

static const u8 magic[] = {
	0xc5, 0x3a, 0xa3, 0x5c, 0xc5, 0x3a, 0xa3, 0x5c
};

/*
 * Read the 64 bit we'd like to have - It a series
 * of 64 bits showing up in the LSB of the base register.
 *
 */
static void ds1216_read(u8 __iomem *ioaddr, u8 *buf)
{
	unsigned char c;
	int i, j;

	for (i = 0; i < 8; i++) {
		c = 0;
		for (j = 0; j < 8; j++)
			c |= (readb(ioaddr) & 0x1) << j;
		buf[i] = c;
	}
}

static void ds1216_write(u8 __iomem *ioaddr, const u8 *buf)
{
	unsigned char c;
	int i, j;

	for (i = 0; i < 8; i++) {
		c = buf[i];
		for (j = 0; j < 8; j++) {
			writeb(c, ioaddr);
			c = c >> 1;
		}
	}
}

static void ds1216_switch_ds_to_clock(u8 __iomem *ioaddr)
{
	/* Reset magic pointer */
	readb(ioaddr);
	/* Write 64 bit magic to DS1216 */
	ds1216_write(ioaddr, magic);
}

static int ds1216_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
	struct ds1216_priv *priv = dev_get_drvdata(dev);
	struct ds1216_regs regs;

	ds1216_switch_ds_to_clock(priv->ioaddr);
	ds1216_read(priv->ioaddr, (u8 *)&regs);

	tm->tm_sec = bcd2bin(regs.sec);
	tm->tm_min = bcd2bin(regs.min);
	if (regs.hour & DS1216_HOUR_1224) {
		/* AM/PM mode */
		tm->tm_hour = bcd2bin(regs.hour & 0x1f);
		if (regs.hour & DS1216_HOUR_AMPM)
			tm->tm_hour += 12;
	} else
		tm->tm_hour = bcd2bin(regs.hour & 0x3f);
	tm->tm_wday = (regs.wday & 7) - 1;
	tm->tm_mday = bcd2bin(regs.mday & 0x3f);
	tm->tm_mon = bcd2bin(regs.month & 0x1f);
	tm->tm_year = bcd2bin(regs.year);
	if (tm->tm_year < 70)
		tm->tm_year += 100;

	return 0;
}

Annotation

Implementation Notes