From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753553Ab3CUVdy (ORCPT ); Thu, 21 Mar 2013 17:33:54 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:34319 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753353Ab3CUVdx (ORCPT ); Thu, 21 Mar 2013 17:33:53 -0400 Date: Thu, 21 Mar 2013 14:33:51 -0700 From: Andrew Morton To: dgilbert@interlog.com Cc: Nicolas Ferre , Jean-Christophe PLAGNIOL-VILLARD , Ludovic Desroches , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] rtc: rtc-at91rm9200: use a variable for storing IMR Message-Id: <20130321143351.3a9c20248e283649334d4251@linux-foundation.org> In-Reply-To: <514A5F2B.8030707@interlog.com> References: <1363369032-12639-1-git-send-email-nicolas.ferre@atmel.com> <20130320145006.f1431c1528325ff93a298790@linux-foundation.org> <514A5F2B.8030707@interlog.com> X-Mailer: Sylpheed 3.2.0beta5 (GTK+ 2.24.10; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 20 Mar 2013 21:15:23 -0400 Douglas Gilbert wrote: > On 13-03-20 05:50 PM, Andrew Morton wrote: > > On Fri, 15 Mar 2013 18:37:12 +0100 Nicolas Ferre wrote: > > > >> On some revisions of AT91 SoCs, the RTC IMR register is not working. > >> Instead of elaborating a workaround for that specific SoC or IP version, > >> we simply use a software variable to store the Interrupt Mask Register and > >> modify it for each enabling/disabling of an interrupt. The overhead of this > >> is negligible anyway. > > > > This description doesn't really allow me or others to work out whether > > the fix should be included in 3.9 or backported into earlier kernels. > > > > So please, when fixing a bug do include a full description of the > > user-visible effects of that bug. And your opinion regarding the > > -mainline and -stable decision is always useful. > > The interrupt mask register (IMR) for the RTC is broken > on the AT91SAM9x5 sub-family of SoCs (good overview of the > members here: http://www.eewiki.net/display/linuxonarm/AT91SAM9x5 ). > The "user visible effect" is the RTC doesn't work. > > That sub-family is less than two years old and only has devicetree > (DT) support and came online circa lk 3.7 . The dust is yet to > settle on the DT stuff at least for AT91 SoCs (translation: > lots of stuff is still broken, so much that it is hard to know > where to start). > > The fix in the patch is pretty simple: just shadow the silicon > IMR register with a variable in the driver. Some older SoCs (pre-DT) > use the the rtc-at91rm9200 driver (e.g. obviously the AT91RM9200) > and they should not be impacted by the change. There shouldn't > be a large volume of interrupts associated with a RTC. Thanks. > Compared to a relatively stable kernel subsystem like SCSI, what > is happening in the ARM architecture with DT is huge and ongoing. > So I think you either need new rules or suspend some of the stricter > rules applied to more stable subsystems. Just my two cents worth. I don't know what this means. Shrug. I tagged the patch for -stable backporting on the basis that "the RTC doesn't work" is undesirable ;)