From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761447AbbBIVii (ORCPT ); Mon, 9 Feb 2015 16:38:38 -0500 Received: from smtp.codeaurora.org ([198.145.29.96]:58108 "EHLO smtp.codeaurora.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761414AbbBIVig (ORCPT ); Mon, 9 Feb 2015 16:38:36 -0500 X-Greylist: delayed 635 seconds by postgrey-1.27 at vger.kernel.org; Mon, 09 Feb 2015 16:38:36 EST Message-ID: <54D9265E.1030403@codeaurora.org> Date: Mon, 09 Feb 2015 13:27:58 -0800 From: Laura Abbott User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0 MIME-Version: 1.0 To: "arnd@arndb.de" , Will Deacon , Robin Murphy CC: devicetree@vger.kernel.org, Laurent Pinchart , Joreg Roedel , linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, Grant Likely , Mitchel Humpherys , linux-arm-kernel@lists.infradead.org, Marek Szyprowski Subject: Re: [PATCH/RFC 0/4] Probe deferral for IOMMU DT integration References: <1423182722-16646-1-git-send-email-lauraa@codeaurora.org> <2115835102.210232.1423348884955.JavaMail.open-xchange@oxbaltgw04.schlund.de> In-Reply-To: <2115835102.210232.1423348884955.JavaMail.open-xchange@oxbaltgw04.schlund.de> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2/7/2015 2:41 PM, arnd@arndb.de wrote: > Laura Abbott hat am 6. Februar 2015 um 01:31 > geschrieben: >> >> The requirement for this is based on a previous patch to add clock >> support to the ARM SMMU driver[2]. Once we have clock support, it's >> possible that the driver itself may need to be defered which breaks >> a bunch of assumptions about how SMMU probing is supposed to work. > > Hi Laura, > > I was hoping that we would not need this, and instead treat the iommu in > the same way as timers and SMP initialization, both > of which need to be run early at boot time but may rely on clock controllers > to be initialized first. > > Is there a specific requirement that makes this impossible here, or is your > intention to solve the problem more nicely by allowing deferred probing > over forcing the input clocks of the iommu to be early? > > Arnd > The current clock driver for qcom targets doesn't support the early initialization needed for timers and SMP because neither of those depend on the clocksources. I discussed this with Stephen some and adding the early support would not mesh well with the device/driver design of the current clock driver so that's not really an option right now. I do think the deferred probing design is cleaner. Even cleaner would be a proper bus type but that's a different can of worms. Thanks, Laura -- Qualcomm Innovation Center, Inc. Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project