From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [PATCH v10 4/6] PCI: hisi: Add PCIe host support for HiSilicon SoC Hip05 Date: Tue, 13 Oct 2015 13:18:33 +0200 Message-ID: <5549505.Kpo7ci0v8h@wuerfel> References: <1444445957-239522-1-git-send-email-wangzhou1@hisilicon.com> <561CA5AF.2080300@hisilicon.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Gabriele Paoloni Cc: "Wangzhou (B)" , Bjorn Helgaas , Bjorn Helgaas , "jingoohan1@gmail.com" , "pratyush.anand@gmail.com" , "linux@arm.linux.org.uk" , "thomas.petazzoni@free-electrons.com" , "lorenzo.pieralisi@arm.com" , "james.morse@arm.com" , "Liviu.Dudau@arm.com" , "jason@lakedaemon.net" , "robh@kernel.org" , "gabriel.fernandez@linaro.org" , "Minghuan.Lian@freescale.com" , "linux-pci@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "devicetree@vger.kernel.org" List-Id: devicetree@vger.kernel.org On Tuesday 13 October 2015 06:58:42 Gabriele Paoloni wrote: > > > >> + > > >> +static int __init hisi_pcie_init(void) > > >> +{ > > >> + return platform_driver_probe(&hisi_pcie_driver, hisi_pcie_probe); > > >> +} > > >> +subsys_initcall(hisi_pcie_init); > > > > > > Can you use module_platform_driver() or module_platform_driver_probe() > > > here instead of the subsys_initcall()? No, I don't really know what > > > the difference between module_platform_driver() and > > > module_platform_driver_probe() is, sorry :) module_platform_driver_probe() will only call the probe function once (and fail in case of -EPROBE_DEFER), while module_platform_driver() installs the platform driver in a way that the device can be bound and unbound at any point. > > In fact, I used module_platform_driver_probe in previous version, but > > A PCIe VGA card of HiSilicon will use Hip05 PCIe host, so we modified > > module_platform_driver_probe to subsys_initcall which will be called > > before module_platform_driver_probe. > > > > We will upstream the driver of above PCIe VGA card soon. I don't see a reason why a VGA driver would need the PCI host to be probed this early, unless it is the only usable console in the system. > Hi Bjorn, firstly many thanks for looking at this. > > About this last bit the reason why we use subsys_initcall() is that > our host bridge is embedded in the SoC and as such is not hot-pluggable > for instance see: > http://lxr.free-electrons.com/source/Documentation/driver-model/platform.txt#L59 We should still be able to build the driver as a loadable module, even if you don't do that on your own kernels. This doesn't mean that it has to be module_platform_driver, subsys_initcall will also work in a loadable module, it just won't be as early. However, we should try to come up with a consistent approach for all PCI host drivers, I don't see any reason for hisi to be different from the others here. > Our approach is also used by Exynos: > http://lxr.free-electrons.com/source/drivers/pci/host/pci-exynos.c#L644 Maybe we should change that too. Arnd