From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753214AbaIEVPu (ORCPT ); Fri, 5 Sep 2014 17:15:50 -0400 Received: from mail-pa0-f46.google.com ([209.85.220.46]:37574 "EHLO mail-pa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751920AbaIEVPs (ORCPT ); Fri, 5 Sep 2014 17:15:48 -0400 Message-ID: <540A27DC.4010206@gmail.com> Date: Fri, 05 Sep 2014 14:15:08 -0700 From: Florian Fainelli User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.0 MIME-Version: 1.0 To: Thomas Gleixner CC: Mark Rutland , LKML , "jason@lakedaemon.net" , "computersforpeace@gmail.com" , "devicetree@vger.kernel.org" Subject: Re: [PATCH 2/2] Documentation: bcm7120-l2: Add Broadcom BCM7120-style L2 binding References: <1409265326-7579-1-git-send-email-f.fainelli@gmail.com> <1409265326-7579-3-git-send-email-f.fainelli@gmail.com> <20140903124317.GB3127@leverpostej> <5407490E.7060505@gmail.com> <20140905090528.GG2172@leverpostej> <5409FA82.6000703@gmail.com> <540A15AA.4000805@gmail.com> In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/05/2014 01:44 PM, Thomas Gleixner wrote: > On Fri, 5 Sep 2014, Florian Fainelli wrote: >> On 09/05/2014 12:21 PM, Thomas Gleixner wrote: >>> So if I understand correctly what you have is: >>> >>> /- GIC-------------> >>> Device-irq ---- [routing] >>> \- BC irq chip ----> >>> >>> and you implement it as >>> >>> Device-irq ---- [BC irq chip] ---- [GIC] ---> >>> | >>> -----------------> >>> >>> And the fwd mask is to tell the BC chip to use the GIC and which irq >>> of the GIC, so it can fiddle with the GIC under the hood, right? >> >> The forward mask really is to tell the BCM7120 l2 interrupt controller: >> bypass me, and output the UART interrupts directly at the GIC level, so >> I think this does match your understanding. >> >> Not setting the forward mask means you would get the UART interrupts at >> the BCM7120 l2 interrupt controller level, and have to handle them here. >> >> Hope this helps clarify what this funky piece of hardware does. > > Sigh, this stacked interrupt chip nonsense is becoming a plague. This is a HW design that we inherited, but fortunately we might be able to fix that in the future. > > So if you set that bit then the UART driver only sees the GIC as its > interrupt controller and not the L2 thingy. So, the L2 chip only > enables its interrupt unconditionally for that line and the > enable/disable happens at the GIC level. Exactly, this is completely transparent for the UART and the GIC. > > If that's the case, that's fine with me. It's not pretty, but at least > it does not involve L2 fiddling indirectly with the GIC. Absolutely, we do not have to do the arch_gic_extn thingy. Thanks for your feedback! -- Florian