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Date: Thu, 21 Mar 2013 14:33:51 -0700 From: Andrew Morton <akpm@...ux-foundation.org> To: dgilbert@...erlog.com Cc: Nicolas Ferre <nicolas.ferre@...el.com>, Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>, Ludovic Desroches <ludovic.desroches@...el.com>, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] rtc: rtc-at91rm9200: use a variable for storing IMR On Wed, 20 Mar 2013 21:15:23 -0400 Douglas Gilbert <dgilbert@...erlog.com> wrote: > On 13-03-20 05:50 PM, Andrew Morton wrote: > > On Fri, 15 Mar 2013 18:37:12 +0100 Nicolas Ferre <nicolas.ferre@...el.com> 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 ;) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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