linux-kernel - [PATCH 1/3] RTC/PCF85063: fix time/date reading (part 1)

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Message-Id: <1449496174-7813-2-git-send-email-jbe@pengutronix.de>
Date:	Mon,  7 Dec 2015 14:49:32 +0100
From:	Juergen Borleis <jbe@...gutronix.de>
To:	rtc-linux@...glegroups.com
Cc:	Alessandro Zummo <a.zummo@...ertech.it>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	linux-kernel@...r.kernel.org, kernel@...gutronix.de
Subject: [PATCH 1/3] RTC/PCF85063: fix time/date reading (part 1)

When reading the seconds register, all time/date registers are frozen
until the year register is read. So, read all time/date registers in one
turn.

Signed-off-by: Juergen Borleis <jbe@...gutronix.de>
---
 drivers/rtc/rtc-pcf85063.c | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/drivers/rtc/rtc-pcf85063.c b/drivers/rtc/rtc-pcf85063.c
index 63334cb..75f2866 100644
--- a/drivers/rtc/rtc-pcf85063.c
+++ b/drivers/rtc/rtc-pcf85063.c
@@ -39,6 +39,38 @@ struct pcf85063 {
 	int voltage_low; /* indicates if a low_voltage was detected */
 };
 
+static int pcf85063_read_time(struct i2c_client *client, u8 *buf, u16 size)
+{
+	int rc;
+	u8 clk_ctrl = PCF85063_REG_SC;
+	struct i2c_msg msgs[] = {
+		{
+			.addr = client->addr,
+			.len = sizeof(clk_ctrl),
+			.buf = &clk_ctrl,
+		}, {
+			.addr = client->addr,
+			.flags = I2C_M_RD,
+			.len = size,
+			.buf = buf
+		},
+	};
+
+	/*
+	 * while reading the time/date registers are blocked and not updated
+	 * anymore until the access is finished. To not lose a second
+	 * event, the access must be finished within one second. So, read all
+	 * time/date registers in one turn.
+	 */
+	rc = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
+	if (rc != ARRAY_SIZE(msgs)) {
+		dev_err(&client->dev, "date/time register read error\n");
+		return -EIO;
+	}
+
+	return 0;
+}
+
 /*
  * In the routines that deal directly with the pcf85063 hardware, we use
  * rtc_time -- month 0-11, hour 0-23, yr = calendar year-epoch.
-- 
2.6.2

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