linux-kernel - Re: [PATCH v3 0/5] rtc-at91rm9200: add shadow interrupt mask

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Date:	Thu, 30 May 2013 19:17:52 -0400
From:	Douglas Gilbert <dgilbert@...erlog.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Nicolas Ferre <nicolas.ferre@...el.com>,
	Robert Nelson <robertcnelson@...il.com>,
	Johan Hovold <jhovold@...il.com>,
	Robert Nelson <Robert.Nelson@...ikey.com>,
	linux-kernel@...r.kernel.org,
	Ludovic Desroches <ludovic.desroches@...el.com>,
	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 0/5] rtc-at91rm9200: add shadow interrupt mask

On 13-05-30 03:36 PM, Andrew Morton wrote:
> On Thu, 30 May 2013 09:50:27 +0200 Nicolas Ferre <nicolas.ferre@...el.com> wrote:
>
>> The review of this patch series was in my TODO list for some time...
>>
>> Today, I magically took time to review it ;-)
>> The patch series is good and I (even if it is too late) here is my:
>>
>> Acked-by: Nicolas Ferre <nicolas.ferre@...el.com>
>>
>> I do not know if the series can be stacked for inclusion in 3.10-rc but
>> the resolution of this bug can help a lot (as Douglas is saying in
>> subsequent email...).
>
> We can do that, but looking through the discussion and changelogs I
> can't seem to find a usable description of what impact the bug (and its
> fix) have upon end-users.
>
> A nicely packaged description of that impact would help grease the
> wheels, please.

How about this:

The members of Atmel's at91sam9x5 family (9x5) have
a broken RTC interrupt mask register (AT91_RTC_IMR).
It does not reflect enabled interrupts but instead
always returns zero.

The kernel's rtc-at91rm9200 driver handles the RTC
for the 9x5 family. Currently when the date/time is
set, an interrupt is generated and this driver neglects
to handle the interrupt. The kernel complains about the
un-handled interrupt and disables it henceforth. This
not only breaks the RTC function, but since that
interrupt is shared (Atmel's SYS interrupt) then other
things break as well (e.g. the debug port no longer
accepts characters).

Tested on the at91sam9g25. Bug confirmed by Atmel.

Edit as you please.

Doug Gilbert

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