From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754583AbdBGToY (ORCPT ); Tue, 7 Feb 2017 14:44:24 -0500 Received: from vern.gendns.com ([206.190.152.46]:34616 "EHLO vern.gendns.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753120AbdBGToW (ORCPT ); Tue, 7 Feb 2017 14:44:22 -0500 Subject: Re: [PATCH v2 1/2] ARM: davinci: Allocate extra interrupts To: Sekhar Nori , linux-arm-kernel@lists.infradead.org References: <1484337612-11120-1-git-send-email-david@lechnology.com> <1484337612-11120-2-git-send-email-david@lechnology.com> <95440160-8346-fef8-27d2-fb17c0da38f6@ti.com> <25c0bc60-bb99-9aa5-db56-6299d82db9c1@lechnology.com> <0bd745dc-df46-0d37-ed18-b419c1cf2e78@ti.com> <139f2c33-7fb3-3a63-6dfe-caa2cca500ce@ti.com> Cc: Kevin Hilman , linux-kernel@vger.kernel.org From: David Lechner Message-ID: Date: Tue, 7 Feb 2017 13:42:55 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0 MIME-Version: 1.0 In-Reply-To: <139f2c33-7fb3-3a63-6dfe-caa2cca500ce@ti.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - vern.gendns.com X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - lechnology.com X-Get-Message-Sender-Via: vern.gendns.com: authenticated_id: davidmain+lechnology.com/only user confirmed/virtual account not confirmed X-Authenticated-Sender: vern.gendns.com: davidmain@lechnology.com X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/02/2017 09:06 AM, Sekhar Nori wrote: > On Friday 20 January 2017 11:47 PM, David Lechner wrote: >> On 01/20/2017 05:50 AM, Sekhar Nori wrote: >>> On Wednesday 18 January 2017 10:27 PM, David Lechner wrote: >>>> On 01/18/2017 03:50 AM, Sekhar Nori wrote: >>>>> On Saturday 14 January 2017 01:30 AM, David Lechner wrote: >>>>>> This allocates extra interrupts for mach-davinci. These extra >>>>>> interrupts >>>>>> are need for things like IIO triggers. >>>>> >>>>> I am not really familiar with IIO triggers. Can you give some more >>>>> detail on what fails without this patch? >>>> >>>> A trigger is used to initiate the reading of an iio device. For example, >>>> there is a mechanism for a sysfs trigger. When you write 1 to the sysfs >>>> attribute, it triggers an interrupt that is handled by the iio device. >>>> >>>> Since these triggers use interrupts, you need to allocate spare >>>> interrupts in order to set up the trigger. Otherwise, setting up the >>>> trigger will fail with an error code (I forgot which one exactly) >>>> because all of the allocated irqs have already been assigned to hardware >>>> irqs and are not available. >>>> >>>> Here is where the iio subsytem actually allocates the irq: >>>> http://lxr.free-electrons.com/source/drivers/iio/industrialio-trigger.c#L525 >>>> >>> >>> Alright, I will take a look. Do note that this may not get included in >>> the first batch of v4.11 changes I queue. But I promise to come back to >>> it soon afterwards. >>> >> >> It is not critical at this point, so it is fine to wait a bit. > > So, I think instead of increasing NR_IRQS by a small number, we should > instead shift to use SPARSE_IRQ. Sounds good. However, this is a bit beyond my expertise. Maybe if I can find a "Sparse IRQ for Dummies" book I could attempt this some time. I looked at some patches from Tony > Lindgren converting OMAP1 to use SPARSE_IRQ. There is some work > involved, but it does not look to be too huge a change to me. > > 685e2d08c54b ARM: OMAP1: Change interrupt numbering for sparse IRQ > b694331cfb2e ARM: omap1: Switch to use MULTI_IRQ > 55b447744389 ARM: OMAP1: Switch to use generic irqchip in preparation for sparse IRQ > 928f81aa619d ARM: OMAP1: Move UART defines to prepare for sparse IRQ > > Thanks, > Sekhar >