[PATCH 3/3] rtc: rs5c348: report error when time is invalid

[Alexandre Belloni <alexandre.belloni@bootlin.com>]

Instead of resetting the RTC to an bogus valid time, let userspace know
that the time is invalid when XSTP is set. Reset XSTP when setting the time
again.

Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
---
 drivers/rtc/rtc-rs5c348.c | 43 +++++++++++++++++++--------------------
 1 file changed, 21 insertions(+), 22 deletions(-)

diff --git a/drivers/rtc/rtc-rs5c348.c b/drivers/rtc/rtc-rs5c348.c
index 7b9c7dc5b309..6582be707bd0 100644
--- a/drivers/rtc/rtc-rs5c348.c
+++ b/drivers/rtc/rtc-rs5c348.c
@@ -66,6 +66,17 @@ rs5c348_rtc_set_time(struct device *dev, struct rtc_time *tm)
 	u8 txbuf[5+7], *txp;
 	int ret;
 
+	ret = spi_w8r8(spi, RS5C348_CMD_R(RS5C348_REG_CTL2));
+	if (ret < 0)
+		return ret;
+	if (ret & RS5C348_BIT_XSTP) {
+		txbuf[0] = RS5C348_CMD_W(RS5C348_REG_CTL2);
+		txbuf[1] = 0;
+		ret = spi_write_then_read(spi, txbuf, 2, NULL, 0);
+		if (ret < 0)
+			return ret;
+	}
+
 	/* Transfer 5 bytes before writing SEC.  This gives 31us for carry. */
 	txp = txbuf;
 	txbuf[0] = RS5C348_CMD_R(RS5C348_REG_CTL2); /* cmd, ctl2 */
@@ -102,6 +113,16 @@ rs5c348_rtc_read_time(struct device *dev, struct rtc_time *tm)
 	u8 txbuf[5], rxbuf[7];
 	int ret;
 
+	ret = spi_w8r8(spi, RS5C348_CMD_R(RS5C348_REG_CTL2));
+	if (ret < 0)
+		return ret;
+	if (ret & RS5C348_BIT_VDET)
+		dev_warn(&spi->dev, "voltage-low detected.\n");
+	if (ret & RS5C348_BIT_XSTP) {
+		dev_warn(&spi->dev, "oscillator-stop detected.\n");
+		return -EINVAL;
+	}
+
 	/* Transfer 5 byte befores reading SEC.  This gives 31us for carry. */
 	txbuf[0] = RS5C348_CMD_R(RS5C348_REG_CTL2); /* cmd, ctl2 */
 	txbuf[1] = 0;	/* dummy */
@@ -165,28 +186,6 @@ static int rs5c348_probe(struct spi_device *spi)
 	dev_info(&spi->dev, "spiclk %u KHz.\n",
 		 (spi->max_speed_hz + 500) / 1000);
 
-	/* turn RTC on if it was not on */
-	ret = spi_w8r8(spi, RS5C348_CMD_R(RS5C348_REG_CTL2));
-	if (ret < 0)
-		return ret;
-	if (ret & (RS5C348_BIT_XSTP | RS5C348_BIT_VDET)) {
-		u8 buf[2];
-		struct rtc_time tm;
-		if (ret & RS5C348_BIT_VDET)
-			dev_warn(&spi->dev, "voltage-low detected.\n");
-		if (ret & RS5C348_BIT_XSTP)
-			dev_warn(&spi->dev, "oscillator-stop detected.\n");
-		rtc_time_to_tm(0, &tm);	/* 1970/1/1 */
-		ret = rs5c348_rtc_set_time(&spi->dev, &tm);
-		if (ret < 0)
-			return ret;
-		buf[0] = RS5C348_CMD_W(RS5C348_REG_CTL2);
-		buf[1] = 0;
-		ret = spi_write_then_read(spi, buf, sizeof(buf), NULL, 0);
-		if (ret < 0)
-			return ret;
-	}
-
 	ret = spi_w8r8(spi, RS5C348_CMD_R(RS5C348_REG_CTL1));
 	if (ret < 0)
 		return ret;
-- 
2.19.0