linux-kernel - [PATCH 3.19.y-ckt 158/164] rtc: ds1307: Fix alarm programming for mcp794xx

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Message-Id: <1449075615-20754-159-git-send-email-kamal@canonical.com>
Date:	Wed,  2 Dec 2015 09:00:09 -0800
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Tero Kristo <t-kristo@...com>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.19.y-ckt 158/164] rtc: ds1307: Fix alarm programming for mcp794xx

3.19.8-ckt11 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Tero Kristo <t-kristo@...com>

commit 62c8c20af92ea312ecb22cec4e83082e5843076b upstream.

mcp794xx alarm registers must be written in BCD format. However, the
alarm programming logic neglected this by adding one to the value
after bin2bcd conversion has been already done, writing bad values
to month register in case the alarm being set is in October. In this
case, the alarm month value becomes 0x0a instead of the expected 0x10.

Fix by moving the +1 addition within the bin2bcd call also.

Fixes: 1d1945d261a2 ("drivers/rtc/rtc-ds1307.c: add alarm support for mcp7941x chips")

Signed-off-by: Tero Kristo <t-kristo@...com>
Acked-by: Nishanth Menon <nm@...com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@...e-electrons.com>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 drivers/rtc/rtc-ds1307.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/rtc/rtc-ds1307.c b/drivers/rtc/rtc-ds1307.c
index 4ffabb3..2e10b39 100644
--- a/drivers/rtc/rtc-ds1307.c
+++ b/drivers/rtc/rtc-ds1307.c
@@ -734,9 +734,9 @@ static int mcp794xx_set_alarm(struct device *dev, struct rtc_wkalrm *t)
 	regs[3] = bin2bcd(t->time.tm_sec);
 	regs[4] = bin2bcd(t->time.tm_min);
 	regs[5] = bin2bcd(t->time.tm_hour);
-	regs[6] = bin2bcd(t->time.tm_wday) + 1;
+	regs[6] = bin2bcd(t->time.tm_wday + 1);
 	regs[7] = bin2bcd(t->time.tm_mday);
-	regs[8] = bin2bcd(t->time.tm_mon) + 1;
+	regs[8] = bin2bcd(t->time.tm_mon + 1);
 
 	/* Clear the alarm 0 interrupt flag. */
 	regs[6] &= ~MCP794XX_BIT_ALMX_IF;
-- 
1.9.1

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