From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758710AbbFAGmr (ORCPT ); Mon, 1 Jun 2015 02:42:47 -0400 Received: from 8bytes.org ([81.169.241.247]:48621 "EHLO theia.8bytes.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750987AbbFAGmk (ORCPT ); Mon, 1 Jun 2015 02:42:40 -0400 Date: Mon, 1 Jun 2015 08:42:38 +0200 From: Joerg Roedel To: Baoquan He Cc: linux-kernel@vger.kernel.org Subject: Re: A question about state machine function state_next() Message-ID: <20150601064238.GC20384@8bytes.org> References: <20150601030940.GK6353@dhcp-128-28.nay.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150601030940.GK6353@dhcp-128-28.nay.redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Baoquan, On Mon, Jun 01, 2015 at 11:09:40AM +0800, Baoquan He wrote: > I am reading amd iommu code because I have some knowledge about intel > iommu since review Zhenhua's fixing kdump error patches. Now there's > a question I didn't find answer. > > In amd iommu state_next() is the state machine running function. However > I only found 4 function to call iommu_go_to_state() to change the state, > they are: > amd_iommu_detect() > amd_iommu_prepare() > amd_iommu_enable() > amd_iommu_init() > > And they are called according to above sequence. It means only below 4 > cases are checked and the code blocks are executed. Then where to call > amd_iommu_enable_interrupts() and amd_iommu_init_dma(). Could you help > to tell what I missed? > > static int __init state_next(void) > { > int ret = 0; > > switch (init_state) { > case IOMMU_START_STATE: //checked and execute > case IOMMU_IVRS_DETECTED: //checked and execute > case IOMMU_ACPI_FINISHED: //checked and execute > case IOMMU_ENABLED: //checked and execute > ... > } Yes, it is right that only these four states are used as exit-states for the functions above. The other states are not really needed, but the work done is these steps is. Originally my idea was to use the intermedite states to see where initialization failed, but that is easier to achieve elsewhere. So this has been on my list of things to clean up, just didn't got around to do it yet. Joerg