From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H. Peter Anvin" Subject: Re: [sodaville] [PATCH 10/15] x86/ioapic: Add OF bindings for IO-APIC Date: Wed, 12 Jan 2011 09:19:53 -0800 Message-ID: <4D2DE2B9.2000607@linux.intel.com> 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> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20110112170707.GA6907-Hfxr4Dq0UpYb1SvskN2V4Q@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org Errors-To: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org To: Sebastian Andrzej Siewior Cc: sodaville-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org, devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org, x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: devicetree@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