From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755354Ab1ALRT6 (ORCPT ); Wed, 12 Jan 2011 12:19:58 -0500 Received: from mga09.intel.com ([134.134.136.24]:23291 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752673Ab1ALRTy (ORCPT ); Wed, 12 Jan 2011 12:19:54 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.60,313,1291622400"; d="scan'208";a="696084743" Message-ID: <4D2DE2B9.2000607@linux.intel.com> Date: Wed, 12 Jan 2011 09:19:53 -0800 From: "H. Peter Anvin" Organization: Intel Open Source Technology Center User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.13) Gecko/20101209 Fedora/3.1.7-0.35.b3pre.fc14 Thunderbird/3.1.7 MIME-Version: 1.0 To: Sebastian Andrzej Siewior CC: Grant Likely , devicetree-discuss@lists.ozlabs.org, sodaville@linutronix.de, x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [sodaville] [PATCH 10/15] x86/ioapic: Add OF bindings for IO-APIC References: <1292600033-12271-1-git-send-email-bigeasy@linutronix.de> <1292600033-12271-11-git-send-email-bigeasy@linutronix.de> <20110111235353.GG2131@angua.secretlab.ca> <20110112170707.GA6907@www.tglx.de> In-Reply-To: <20110112170707.GA6907@www.tglx.de> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/12/2011 09:07 AM, Sebastian Andrzej Siewior wrote: >> >> I'm confused here. Are there multiple ioapic's described by a single >> device tree node? > > Yes, the CE4100 has two IO-APICs. It looks like the first one is > responsible for the "legacy devices" (like RTC) and the second one is > used for the "extra devices" like SPI controller, USB, ... The UART > however is not on the first IO-APIC but on the second. > > Those two IO-APICs are not cascaded. The device tree contains the line > number of device to the io apic. The kernel computes then interrupt > number based on gsi_base + line_number where gsi_base is incremented by > the number of entries[0]. This interrupt number (gsi_base + line) is then > sent via apic bus to lapic which reports it as the active interrupt > source. > That's normal multiple IOAPIC behavior (and multiple IOAPICs is a common thing), but why use the same device tree node for both? -hpa