linux-kernel - [PATCH 2/6] rtc: pcf8563 Fix write of invalid bits to ST2 reg

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Message-Id: <1414419421-11098-3-git-send-email-jan.kardell@telliq.com>
Date:	Mon, 27 Oct 2014 15:16:57 +0100
From:	Jan Kardell <jan.kardell@...liq.com>
To:	Alessandro Zummo <a.zummo@...ertech.it>,
	rtc-linux@...glegroups.com, linux-kernel@...r.kernel.org
Cc:	Vincent Donnefort <vdonnefort@...il.com>,
	Dan Carpenter <dan.carpenter@...cle.com>
Subject: [PATCH 2/6] rtc: pcf8563 Fix write of invalid bits to ST2 reg

>From the NXP datasheet:
"Bits labeled as N should always be written with logic 0."

At least one of those bits is sometime read as a 1, therfore violating
this rule. To fix this we mask away those bits.

Signed-off-by: Jan Kardell <jan.kardell@...liq.com>
---
 drivers/rtc/rtc-pcf8563.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/rtc/rtc-pcf8563.c b/drivers/rtc/rtc-pcf8563.c
index 1a865c9..8c23606 100644
--- a/drivers/rtc/rtc-pcf8563.c
+++ b/drivers/rtc/rtc-pcf8563.c
@@ -28,6 +28,7 @@
 #define PCF8563_REG_ST2		0x01
 #define PCF8563_BIT_AIE		(1 << 1)
 #define PCF8563_BIT_AF		(1 << 3)
+#define PCF8563_BITS_ST2_N	(7 << 5)
 
 #define PCF8563_REG_SC		0x02 /* datetime */
 #define PCF8563_REG_MN		0x03
@@ -130,7 +131,7 @@ static int pcf8563_set_alarm_mode(struct i2c_client *client, bool on)
 	else
 		buf &= ~PCF8563_BIT_AIE;
 
-	buf &= ~PCF8563_BIT_AF;
+	buf &= ~(PCF8563_BIT_AF | PCF8563_BITS_ST2_N);
 
 	err = pcf8563_write_block_data(client, PCF8563_REG_ST2, 1, &buf);
 	if (err < 0) {
-- 
1.8.4.5

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