linux-kernel - Re: [rtc-linux] [PATCH] RTC: RK808: Work around hardware bug on November 31st

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Date:	Thu, 3 Dec 2015 15:42:03 +0100
From:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To:	Julius Werner <jwerner@...omium.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	Doug Anderson <dianders@...omium.org>,
	Sonny Rao <sonnyrao@...omium.org>,
	Chris Zhong <zyw@...k-chips.com>,
	Heiko Stuebner <heiko@...ech.de>, linux-kernel@...r.kernel.org,
	rtc-linux@...glegroups.com
Subject: Re: [rtc-linux] [PATCH] RTC: RK808: Work around hardware bug on
 November 31st

Hi,

I would have liked to be in copy of that mail. Maybe you used
get_maintainers on an old tree?

On 02/12/2015 at 17:53:04 -0800, Julius Werner wrote :
> In Fuzhou, China, the month of November seems to be having 31 days.
> That's nice and all (I'm sure you can get a lot more done in a year that
> way), but back here in other parts of the world we are not so lucky.
> Therefore, if we read that date from the RTC we should correct it to
> December 1st.
> 

Wow, nice one...

I hope reading the time properly fails thanks to the rtc_valid_tm(tm) in
__rtc_read_time().

> This is not a full workaround. Since the RTC actually ticks all the way
> through that imaginary day, there's no easy way to detect and correct
> this issue if the device was offline the whole time and allowed it to
> tick through to December 1st on the Rockchip calendar (which would be
> December 2nd on the Gregorian one). Those edge cases can only really be
> solved by regularly syncing to an external time source (e.g. NTP).
> 

It will also happen if nobody reads the RTC time for that day (highly
improbable in a default configuration). Do you need that patch for 4.4
or can it wait 4.5?


> Signed-off-by: Julius Werner <jwerner@...omium.org>
> Reviewed-by: Chris Zhong <zyw@...k-chips.com>
> ---
>  drivers/rtc/rtc-rk808.c | 93 ++++++++++++++++++++++++++-----------------------
>  1 file changed, 50 insertions(+), 43 deletions(-)
> 

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