From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Courtier-Dutton Subject: Re: ACPI vs. ISA IRQs Date: Wed, 05 Nov 2003 00:03:08 +0000 Sender: acpi-devel-admin-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Message-ID: <3FA83E3C.6070907@superbug.demon.co.uk> References: <1067981294.6057.20.camel@dhcppc4> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1067981294.6057.20.camel-D2Zvc0uNKG8@public.gmane.org> Errors-To: acpi-devel-admin-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Help: List-Post: List-Subscribe: , List-Unsubscribe: , List-Archive: To: Len Brown Cc: ACPI Developers , linux-acpi List-Id: linux-acpi@vger.kernel.org Len Brown wrote: > Assumption: sharing interrupts is bad. > > Plan: > ACPI should attempt to distribute interrupts across > the available IRQs. > > This mostly applies to PIC mode, where PCI > IRQ Link Devices are available to route PCI > interrupts to open IRQs on the PIC. > (In IO-APIC mode, we generally get no choice > which IO-APIC pins devices are attached to) > > We have acpi_irq_penalty[] (disabled at the moment) > in pci_link.c hard-coded to tell ACPI to avoid some IRQs > that are commonly used by ISA devices. > > But if,say, a sound-blaster card requests exclusive access > to an IRQ that we didn't happen to reserve, and we happened > to set a PCI link device to that IRQ, then sound doesn't > work. > > How to fix? > > We can manually reserve IRQs to over-ride acpi_irq_penalty[], > say "acpi_irq_used=5,10" to tell ACPI not to use IRQs that > it thought by default were available. > > Conversely, we could us, say, "acpi_irq_free=3,15" to tell > ACPI that some IRQs it assumed were reserved for ISA are > actually available for PCI. > > I don't know of an automatic way to handle this. > Seems that the ISA devices use Plug-and-Play methods > to request IRQs, but there is no mechanism for such > an event to boot a PIRQ off an IRQ if ACPI has put it there. > Also, if such a mechanism existed, it wouldn't work > if PNP were not available to ask for an IRQ. > > thoughts? > > thanks, > -Len > > ref: > http://bugzilla.kernel.org/show_bug.cgi?id=430 > http://bugzilla.kernel.org/show_bug.cgi?id=1139 > http://bugzilla.kernel.org/show_bug.cgi?id=1391 > > This explains IRQs a bit: - http://www.microsoft.com/whdc/hwdev/platform/proc/IO-APIC.mspx ------------------------------------------------------- This SF.net email is sponsored by: SF.net Giveback Program. Does SourceForge.net help you be more productive? Does it help you create better code? SHARE THE LOVE, and help us help YOU! Click Here: http://sourceforge.net/donate/