Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751497AbcDPOgr (ORCPT ); Sat, 16 Apr 2016 10:36:47 -0400 Received: from mail-yw0-f180.google.com ([209.85.161.180]:34306 "EHLO mail-yw0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751333AbcDPOgo (ORCPT ); Sat, 16 Apr 2016 10:36:44 -0400 MIME-Version: 1.0 In-Reply-To: <4240660.NqlPcXaV7N@wuerfel> References: <1460740008-19489-1-git-send-email-tn@semihalf.com> <5110401.mGEq6IVFz2@wuerfel> <4240660.NqlPcXaV7N@wuerfel> From: Jayachandran C Date: Sat, 16 Apr 2016 20:06:03 +0530 Message-ID: Subject: Re: [PATCH V6 08/13] PCI: generic, thunder: update to use generic ECAM API To: Arnd Bergmann Cc: linux-arm-kernel@lists.infradead.org, Tomasz Nowicki , Bjorn Helgaas , Will Deacon , Catalin Marinas , rafael@kernel.org, Hanjun Guo , Lorenzo Pieralisi , Sinan Kaya , jiang.liu@linux.intel.com, Jon Masters , linaro-acpi@lists.linaro.org, linux-pci@vger.kernel.org, Liviu.Dudau@arm.com, David Daney , linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, robert.richter@caviumnetworks.com, Suravee.Suthikulpanit@amd.com, msalter@redhat.com, Wangyijing , Marcin Wojtas Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2502 Lines: 54 On Sat, Apr 16, 2016 at 1:01 PM, Arnd Bergmann wrote: > On Saturday 16 April 2016 12:50:13 Jayachandran C wrote: >> > >> > I still think it would be better to keep the loadable PCI host drivers >> > separate from the ACPI PCI infrastructure. There are a number of >> > simplifications that we want to do to the DT based drivers in the long >> > run, so it's better if that code is not shared at this level. Abstracting >> > out the ECAM code is fine, but at that point you should be able to just >> > call it from the ACPI layer. >> >> The issue is not with this patch (in my opinion). This patch is just >> re-arranging how thunder specific data is maintained. Earlier it was >> a container_of gen_pci, now it is ->priv of pci_config_window. >> >> I can see the issue in patches 12 and 13 of this patchset which adds >> ACPI fixups into the thunder OF driver. > > Right, I commented on this one, because it seems to rearrange the code > in order to do the later one. Patches 11- 13 are not from me, and I am not completely on board on the approach of adding the sections.We can look at reworking this. >> The simple approach when doing modular PCI drivers would be to make >> pci-thunder-*.c like pci-host-common.c, to be compiled in if configured. >> The fie will contain all the Thunder quirks and can export >> pci_thunder_ecam_ops. > > I would argue that we should not export anything from drivers/pci/host, > those should really be standalone drivers that do not interact with other > subsystems. pci-host-common.c goes against being standalone. The files calling pci_host_common_probe() are expected to have custom ECAM ops the way it is written now. We need to have a reasonable way to share those ECAM ops if needed by ACPI. > How much code would you need to duplicate from thunder-ecam to have > the same functionality available in ACPI? My expectation is that it's > not really that much more compared to the code you need for sharing > a single implementation, but you get a lower complexity here, which > makes it easier to understand and to rework. Like I wrote above, the sharing is really simple because both generic ACPI and pci-host-common.c have been written for "ECAM with quirks". The whole pci-thunder-*.c is to support thunder PCI quirks since the generic OF is handled by pci-host-common.c and generic ECAM is now separated - duplicating the whole file for ACPI will be bad. Any suggestions on how to do this better would be really welcome. Thanks, JC.