From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756605AbcARUaS (ORCPT ); Mon, 18 Jan 2016 15:30:18 -0500 Received: from www.linutronix.de ([62.245.132.108]:48348 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756407AbcARUaQ (ORCPT ); Mon, 18 Jan 2016 15:30:16 -0500 Subject: Re: Fix preempt-rt on AT91 To: Alexandre Belloni References: <1452997394-8554-1-git-send-email-alexandre.belloni@free-electrons.com> <20160118174259.GC12309@linutronix.de> <20160118192308.GR3367@piout.net> Cc: Thomas Gleixner , Boris Brezillon , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org, Nicolas Ferre From: Sebastian Andrzej Siewior X-Enigmail-Draft-Status: N1110 Message-ID: <569D4B55.10103@linutronix.de> Date: Mon, 18 Jan 2016 21:30:13 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Icedove/38.5.0 MIME-Version: 1.0 In-Reply-To: <20160118192308.GR3367@piout.net> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/18/2016 08:23 PM, Alexandre Belloni wrote: > Hi, Hi, >>> I'd say that the proper solution would still be to implement the virtual >>> irqchip because this would still hit people not wanting to use the TCB as >>> their clock source. >> >> why wouldn't people not want that? > > Because they may be using the TCBs for something else: PWM, frequency > measure, quadrature decoder... Oh okay. >> For a virtual irqchip you would need a mask/unmask register in order to >> individual disable/enable the irq and you need something to figure out >> which one of the three is active. You don't have all those things, do >> you? >> > > The proposed solution was software only. It mainly consisted in a simple > irq demuxer. Well, if it works properly and does not lead to any new bugs or anything else then nobody will mind I guess. >> All in all, care to forwarded the working pieces from -RT patch set >> upstream? I problem I have here is mostly that I can't the patches on >> actual hardware. Disabling the PIT and running on the other clocksource >> isn't that -RT specific after all :) > > I'd say that the only remaining part is the IRQ freeing/requesting but > as I said, this can't land in mainline as is. I still plan to work on > that later. > I'd say that most people running linux on at91 are already using the tcb > as the clocksource, this is already available in the mainline and is the > default unless the TCBs are used for something else. Wasn't there one of the patches to increase the frequency of the TCB clocksource from the default to something higher? Sebastian