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Groups > linux.kernel > #1254358 > unrolled thread

[PATCH] rtc: ds1307: Fix alarm programming for mcp794xx

Started byTero Kristo <t-kristo@ti.com>
First post2015-10-23 08:40 +0200
Last post2015-10-28 00:00 +0100
Articles 3 — 3 participants

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  [PATCH] rtc: ds1307: Fix alarm programming for mcp794xx Tero Kristo <t-kristo@ti.com> - 2015-10-23 08:40 +0200
    Re: [PATCH] rtc: ds1307: Fix alarm programming for mcp794xx Nishanth Menon <nm@ti.com> - 2015-10-24 16:50 +0200
    Re: [PATCH] rtc: ds1307: Fix alarm programming for mcp794xx Alexandre Belloni <alexandre.belloni@free-electrons.com> - 2015-10-28 00:00 +0100

#1254358 — [PATCH] rtc: ds1307: Fix alarm programming for mcp794xx

FromTero Kristo <t-kristo@ti.com>
Date2015-10-23 08:40 +0200
Subject[PATCH] rtc: ds1307: Fix alarm programming for mcp794xx
Message-ID<qmEb8-1Kb-5@gated-at.bofh.it>
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@ti.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 a705e64..188006c 100644
--- a/drivers/rtc/rtc-ds1307.c
+++ b/drivers/rtc/rtc-ds1307.c
@@ -718,9 +718,9 @@ 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;
-- 
1.7.9.5

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#1255192

FromNishanth Menon <nm@ti.com>
Date2015-10-24 16:50 +0200
Message-ID<qn8iR-3eL-7@gated-at.bofh.it>
In reply to#1254358
On 10/23/2015 01:29 AM, Tero Kristo wrote:
> 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@ti.com>

Nice catch.
Acked-by: Nishanth Menon <nm@ti.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 a705e64..188006c 100644
> --- a/drivers/rtc/rtc-ds1307.c
> +++ b/drivers/rtc/rtc-ds1307.c
> @@ -718,9 +718,9 @@ 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;
> 


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Regards,
Nishanth Menon
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#1257453

FromAlexandre Belloni <alexandre.belloni@free-electrons.com>
Date2015-10-28 00:00 +0100
Message-ID<qolnI-2I6-15@gated-at.bofh.it>
In reply to#1254358
On 23/10/2015 at 09:29:57 +0300, Tero Kristo wrote :
> 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@ti.com>
> ---
>  drivers/rtc/rtc-ds1307.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
Applied, thanks.

-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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