From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Garzik Subject: Re: [patch] PCI: disable MSI on more ATI NorthBridges Date: Mon, 22 Oct 2007 16:41:00 -0400 Message-ID: <471D0ADC.7000005@garzik.org> References: <20071019195749.GK29903@austin.ibm.com> <471911BE.2000405@garzik.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Daniel Barkalow Cc: Linas Vepstas , Shane Huang , davem@davemloft.net, gregkh@suse.de, htejun@gmail.com, brice.goglin@gmail.com, david.gaarenstroom@gmail.com, linux-kernel@vger.kernel.org, linux-pci@atrey.karlin.mff.cuni.cz, shane.huang@amd.com, linux-ide@vger.kernel.org, Brice Goglin List-Id: linux-ide@vger.kernel.org Daniel Barkalow wrote: > On Fri, 19 Oct 2007, Jeff Garzik wrote: > >> Linas Vepstas wrote: >>> On Fri, Oct 19, 2007 at 09:17:23PM +0800, Shane Huang wrote: >>>> Since we have little experience on PCI and MSI here, we had to try to >>> As someone else pointed out, AMD should have *lots* of people with >>> pci and msi experience on the payroll. (Folks here buy AMD-designed pci >>> chips ...) >>> >>>> ONLY >>>> comment out the pci_intx() call in drivers/ata/ahci.c >>>> My system can boot up too with MSI enabled! >>>> >>>> So does it mean that the root cause is our SB700 SATA controller >>>> has a hardware bug where setting INTX_DISABLE in the PCI COMMAND >>>> register masks MSI interrupts too? >>> That's what it sounds like, to me. >>> >>>> And what is the software solution or workaround? >>> Not sure. Sounds like the device driver needs a quirk for this part. >> >> Take a look at tg3.c net driver change >> 2fbe43f6f631dd7ce19fb1499d6164a5bdb34568 which is a similar situation. >> >> However, it may turn out that removing the pci_intx() stuff as a general rule >> is easier than quirking these devices, if enough of them turn out to have this >> hardware bug. > > At a first approximation, ATI/AMD devices don't send any interrupts if > intx is disabled, nVidia devices send legacy interrupts in addition to MSI > ones if intx isn't disabled, and Intel devices actually work correctly. So > we need at least one kind of device quirk for intx and msi. (And doing it > in the drivers doesn't work, since everybody is making things driven by > snd_hda_intel and would like msi, afaict) Note that INTX_DISABLE is a recent addition to PCI. Older PCI devices support neither MSI nor INTX-disable, so make sure such devices don't creep into your sample. In general it is documented that INTX_DISABLE should apply only to INTx# so devices that disable MSI based on that bit are out of spec. But unfortunately that is rather irrelevant, since we see these out-of-spec devices in the field today. Jeff