Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752179AbdGGPmx (ORCPT ); Fri, 7 Jul 2017 11:42:53 -0400 Received: from foss.arm.com ([217.140.101.70]:48708 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751023AbdGGPmv (ORCPT ); Fri, 7 Jul 2017 11:42:51 -0400 Subject: Re: [RFC PATCH 1/2] dt-bindings: pci: Add drop mask property for MSI and IOMMU To: Scott Branden , Mark Rutland , Srinath Mannam Cc: devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, Rob Herring , bcm-kernel-feedback-list@broadcom.com, Bjorn Helgaas , Frank Rowand References: <1499411399-25103-1-git-send-email-srinath.mannam@broadcom.com> <1499411399-25103-2-git-send-email-srinath.mannam@broadcom.com> <20170707133052.GB3425@leverpostej> <89f871d1-fc28-aa0b-2460-cf834e7e99f6@arm.com> From: Robin Murphy Message-ID: Date: Fri, 7 Jul 2017 16:42:48 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1257 Lines: 27 On 07/07/17 16:22, Scott Branden wrote: > Hi Robin, > > On 17-07-07 07:55 AM, Robin Murphy wrote: >> On 07/07/17 14:30, Mark Rutland wrote: [...] >>> Your mapping can be expressed today using a number of msi-map entries, >>> which you can easily generate programmatically with a trivial perl >>> script, without requiring a new binding or any new kernel code. >>> >>> Please do that instead. >> Indeed. The systems I'm aware of which need to express non-trivial RID >> to SID mappings tend to have the bootloader probe PCI and dynamically >> generate map entries per discovered RID, but even if you wanted to >> statically generate the whole lot for the worst-case bus range that's >> still only 512 entries, which is not unmanageable. Notably, it's also >> what would have to be done (in equivalent) for IORT, although I assume >> this is an embedded platform for which nobody cares about ACPI. > Actually we will care about ACPI and need to add it (doesn't need to be > in this patchet unless easy to do so...) Ah, OK, that's an even stronger argument for not adding anything new then - DT "iommu-map" is already marginally more expressive than IORT ID mappings can be, so there doesn't seem to be much justification for diverging them further. Robin.