Re: [PATCH v3 3/5] rtc: pcf2127: bugfix: read rtc disables watchdog

From: Alexandre Belloni <alexandre.belloni@bootlin.com>
To: Bruno Thomsen <bruno.thomsen@gmail.com>
Cc: linux-rtc@vger.kernel.org, linux-watchdog@vger.kernel.org,
	a.zummo@towertech.it, wim@linux-watchdog.org, linux@roeck-us.net,
	u.kleine-koenig@pengutronix.de, bth@kamstrup.com
Subject: Re: [PATCH v3 3/5] rtc: pcf2127: bugfix: read rtc disables watchdog
Date: Thu, 22 Aug 2019 23:28:25 +0200	[thread overview]
Message-ID: <20190822212825.GI27031@piout.net> (raw)
In-Reply-To: <20190822131936.18772-3-bruno.thomsen@gmail.com>

On 22/08/2019 15:19:34+0200, Bruno Thomsen wrote:
> The previous fix listed bulk read of registers as root cause of
> accendential disabling of watchdog, since the watchdog counter
> register (WD_VAL) was zeroed.
> 
> Fixes: 3769a375ab83 rtc: pcf2127: bulk read only date and time registers.
> 
> Tested with the same PCF2127 chip as Sean reveled root cause
> of WD_VAL register value zeroing was caused by reading CTRL2
> register which is one of the watchdog feature control registers.
> 
> So the solution is to not read the first two control registers
> (CTRL1 and CTRL2) in pcf2127_rtc_read_time as they are not
> needed anyway. Size of local buf variable is kept to allow
> easy usage of register defines to improve readability of code.
> 
> Debug trace line was updated after CTRL1 and CTRL2 are no longer
> read from the chip. Also replaced magic numbers in buf access
> with register defines.
> 
> Signed-off-by: Bruno Thomsen <bruno.thomsen@gmail.com>
> ---
> v3: no change.
> v2: new bugfix, not in v1.
> 
>  drivers/rtc/rtc-pcf2127.c | 32 ++++++++++++--------------------
>  1 file changed, 12 insertions(+), 20 deletions(-)
> 
Applied, thanks.

-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com