From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julien Grall Subject: Re: Design doc of adding ACPI support for arm64 on Xen Date: Wed, 5 Aug 2015 14:25:51 +0100 Message-ID: <55C20EDF.9010909@citrix.com> References: <55C0C17F.5040208@huawei.com> <55C1D783.3020908@huawei.com> <55C1F840.9060002@linaro.org> <55C20600.9070104@citrix.com> <55C2098A.6070300@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <55C2098A.6070300@linaro.org> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Shannon Zhao , Stefano Stabellini , Shannon Zhao Cc: Hangaohuai , Ian Campbell , "Huangpeng (Peter)" , xen-devel , Stefano Stabellini , Jan Beulich , parth.dixit@linaro.org, Christoffer Dall List-Id: xen-devel@lists.xenproject.org On 05/08/15 14:03, Shannon Zhao wrote: > > > On 2015/8/5 20:48, Julien Grall wrote: >> On 05/08/15 12:49, Shannon Zhao wrote: >>>> >>That's great! >>>> >>Keep in mind that many ARM platforms have non-PCI busses, so I think >>>> >>we'll need an amba and a platform bus_notifier too, in addition to >>>> the >>>> >>existing pci bus notifier. >>>> >> >>> > >>> >Thanks for your reminding. I thought about amba. Since ACPI of current >>> >linux kernel doesn't support probe amba bus devices, so this >>> >bus_notifier will not be used at the moment. But there are some voice >>> >that we need to make ACPI support amba on the linux arm kernel mail >>> >list. And to me it doesn't matter to add the amba bus_notifier. >> This comment raised one question. What happen if the hardware has MMIO >> region not described in the ACPI? >> > This sounds weird. If a device is described in ACPI table, it will not > describe the MMIO region which the driver will use? Does this situation > exist? Buggy ACPI tables, not possible to describe the ACPI ... There is plenty of reason. I don't know if there is current problem on ACPI (I don't have much work with it). But it presents on the device tree. We may a lots of specific platform mapping in Xen (see specific_mapping) because of buggy DT. We can't rule out and needs to provide a way to cope with this. If we don't do it, it will fall on us sooner or later. > If the hardware has mmio region not described in the ACPI, how does the > driver know the region and use it? Hardcoded. Regards, -- Julien Grall