rtc: pcf2123: implement read_offset and set_offset (bae2f647) · Commits · 戴 / test

drivers/rtc/rtc-pcf2123.c

+57 −0

Original line number	Diff line number	Diff line
		@@ -100,6 +100,7 @@
		/* PCF2123_REG_OFFSET BITS */
		#define OFFSET_SIGN_BIT BIT(6) /* 2's complement sign bit */
		#define OFFSET_COARSE BIT(7) /* Coarse mode offset */
		#define OFFSET_STEP (2170) /* Offset step in parts per billion */

		/* READ/WRITE ADDRESS BITS */
		#define PCF2123_WRITE BIT(4)
		@@ -206,6 +207,59 @@ static ssize_t pcf2123_store(struct device dev, struct device_attribute attr,
		return count;
		}

		static int pcf2123_read_offset(struct device dev, long offset)
		{
		int ret;
		s8 reg;

		ret = pcf2123_read(dev, PCF2123_REG_OFFSET, &reg, 1);
		if (ret < 0)
		return ret;

		if (reg & OFFSET_COARSE)
		reg <<= 1; /* multiply by 2 and sign extend */
		else
		reg \|= (reg & OFFSET_SIGN_BIT) << 1; /* sign extend only */

		offset = ((long)reg) OFFSET_STEP;

		return 0;
		}

		/*
		* The offset register is a 7 bit signed value with a coarse bit in bit 7.
		* The main difference between the two is normal offset adjusts the first
		* second of n minutes every other hour, with 61, 62 and 63 being shoved
		* into the 60th minute.
		* The coarse adjustment does the same, but every hour.
		* the two overlap, with every even normal offset value corresponding
		* to a coarse offset. Based on this algorithm, it seems that despite the
		* name, coarse offset is a better fit for overlapping values.
		*/
		static int pcf2123_set_offset(struct device *dev, long offset)
		{
		s8 reg;

		if (offset > OFFSET_STEP * 127)
		reg = 127;
		else if (offset < OFFSET_STEP * -128)
		reg = -128;
		else
		reg = (s8)((offset + (OFFSET_STEP >> 1)) / OFFSET_STEP);

		/* choose fine offset only for odd values in the normal range */
		if (reg & 1 && reg <= 63 && reg >= -64) {
		/* Normal offset. Clear the coarse bit */
		reg &= ~OFFSET_COARSE;
		} else {
		/* Coarse offset. Divide by 2 and set the coarse bit */
		reg >>= 1;
		reg \|= OFFSET_COARSE;
		}

		return pcf2123_write_reg(dev, PCF2123_REG_OFFSET, reg);
		}

		static int pcf2123_rtc_read_time(struct device dev, struct rtc_time tm)
		{
		u8 rxbuf[7];
		@@ -314,6 +368,9 @@ static int pcf2123_reset(struct device *dev)
		static const struct rtc_class_ops pcf2123_rtc_ops = {
		.read_time = pcf2123_rtc_read_time,
		.set_time = pcf2123_rtc_set_time,
		.read_offset = pcf2123_read_offset,
		.set_offset = pcf2123_set_offset,

		};

		static int pcf2123_probe(struct spi_device *spi)

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