From mboxrd@z Thu Jan 1 00:00:00 1970 From: Laura Abbott Subject: Re: [PATCH/RFC 0/4] Probe deferral for IOMMU DT integration Date: Mon, 09 Feb 2015 13:27:58 -0800 Message-ID: <54D9265E.1030403@codeaurora.org> References: <1423182722-16646-1-git-send-email-lauraa@codeaurora.org> <2115835102.210232.1423348884955.JavaMail.open-xchange@oxbaltgw04.schlund.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <2115835102.210232.1423348884955.JavaMail.open-xchange@oxbaltgw04.schlund.de> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org 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 List-Id: devicetree@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