Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754965AbaAWXFT (ORCPT ); Thu, 23 Jan 2014 18:05:19 -0500 Received: from mail-ee0-f47.google.com ([74.125.83.47]:45911 "EHLO mail-ee0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751184AbaAWXFQ (ORCPT ); Thu, 23 Jan 2014 18:05:16 -0500 Message-ID: <52E1A028.6020309@gmail.com> Date: Fri, 24 Jan 2014 00:05:12 +0100 From: Sebastian Hesselbarth User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 To: Jason Gunthorpe CC: Thomas Gleixner , Jason Cooper , Andrew Lunn , Gregory Clement , Ezequiel Garcia , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 3/3] irqchip: orion: clear stale interrupts in irq_enable References: <1390516686-2224-1-git-send-email-sebastian.hesselbarth@gmail.com> <1390516686-2224-4-git-send-email-sebastian.hesselbarth@gmail.com> <20140123225208.GA24778@obsidianresearch.com> In-Reply-To: <20140123225208.GA24778@obsidianresearch.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/23/2014 11:52 PM, Jason Gunthorpe wrote: > On Thu, Jan 23, 2014 at 11:38:06PM +0100, Sebastian Hesselbarth wrote: >> Bridge IRQ_CAUSE bits are asserted regardless of the corresponding bit in >> IRQ_MASK register. To avoid interrupt events on stale irqs, we have to clear >> them before unmask. This installs an .irq_enable callback to ensure stale >> irqs are cleared before initial unmask. > > I'm not sure if putting this in irq_enable is correct. I think this > should only happen at irq_startup. > > The question boils down to what is supposed to happen with this code > sequence: > > disable_irq(..); > write(.. something to cause an interrupt edge ..); > .. synchronize .. > enable_irq(..); > > Do we get the interrupt or not? Jason, I get the point and actually I'd chosen .irq_enable because using .irq_startup didn't work. I rechecked this and now it works.. maybe it is getting too late for me. I'll send a v2 of this patch shortly. Sebastian > I found this message from Linus long ago: > http://yarchive.net/comp/linux/edge_triggered_interrupts.html >> Btw, the "disable_irq()/enable_irq()" subsystem has been written so that >> when you disable an edge-triggered interrupt, and the edge happens while >> the interrupt is disabled, we will re-play the interrupt at enable time. >> Exactly so that drivers can have an easier time and don't have to >> normally worry about whether something is edge or level-triggered. > > And found this note in Documentation/DocBook/genericirq.tmpl: > >> This prevents losing edge interrupts on hardware which does >> not store an edge interrupt event while the interrupt is disabled at >> the hardware level. > > So I think it is very clear that the chip driver should not discard > edges that happened while the interrupt was disabled. > > Regards, > Jason > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/