Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030632AbWKOQUT (ORCPT ); Wed, 15 Nov 2006 11:20:19 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030646AbWKOQUT (ORCPT ); Wed, 15 Nov 2006 11:20:19 -0500 Received: from smtp.osdl.org ([65.172.181.4]:39650 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S1030632AbWKOQUQ (ORCPT ); Wed, 15 Nov 2006 11:20:16 -0500 Date: Wed, 15 Nov 2006 08:19:05 -0800 (PST) From: Linus Torvalds To: Takashi Iwai cc: David Miller , jeff@garzik.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] ALSA: hda-intel - Disable MSI support by default In-Reply-To: Message-ID: References: <20061114.190036.30187059.davem@davemloft.net> <20061114.192117.112621278.davem@davemloft.net> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1690 Lines: 39 On Wed, 15 Nov 2006, Takashi Iwai wrote: > > The snd-hda-intel driver has a test of MSI, but it seems not working > on every machine. It caused non-cared interrupts and the kernel > disabled that irq. Yes. Btw, this was why I was claiming that maybe some devices might raise _both_ the MSI and the INTx interrupt, which can indeed cause problems like that: because we see spurious interrupts on some other irq line (the INTx one), we might decide to end up disabling that one, just because we can't seem to shut it up. However, the same kind of schenario may happen if the MSI irq from a device simply doesn't _work_ - the device may claim MSI capabilities but always uses INTx, and you'd get the same behaviour from just _testing_ the MSI line - the irq comes in on the wrong vector, and since you're not handling that vector, the kernel has no choice but to say "I will have to disable this screaming irq". So "testing" that an MSI works isn't actually goign to solve any real problems. It may or may not show that the MSI works, but regardless of the success of the test, it can have deadly consequences for _other_ devices if the irq routing (which may be INTx) is broken. This is why I'm so adamant that we need to _know_ that it works before we use it. When irq's get mis-routed, things go downhill real fast. We're usually talking "dead machines", and there is very little that a driver can do about it. Linus - 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/