Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751582AbdHEGRC (ORCPT ); Sat, 5 Aug 2017 02:17:02 -0400 Received: from mailgw01.mediatek.com ([210.61.82.183]:12865 "EHLO mailgw01.mediatek.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1751396AbdHEGRA (ORCPT ); Sat, 5 Aug 2017 02:17:00 -0400 Message-ID: <1501913813.12086.17.camel@mtkswgap22> Subject: Re: [PATCH v2 4/5] PCI: mediatek: Add new generation controller support From: Ryder Lee To: Bjorn Helgaas CC: Honghui Zhang , , , , , , , , , , , , , , , , , Date: Sat, 5 Aug 2017 14:16:53 +0800 In-Reply-To: <1501908763.8298.11.camel@mtkswgap22> References: <824c61d13fe2731d812df8a0a878ca1a36399e76.1501122135.git.honghui.zhang@mediatek.com> <20170803224206.GN20308@bhelgaas-glaptop.roam.corp.google.com> <1501835976.24341.21.camel@mtksdaap41> <20170804131808.GA16580@bhelgaas-glaptop.roam.corp.google.com> <1501908763.8298.11.camel@mtkswgap22> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3-0ubuntu6 Content-Transfer-Encoding: 7bit MIME-Version: 1.0 X-MTK: N Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2945 Lines: 69 On Sat, 2017-08-05 at 12:52 +0800, Ryder Lee wrote: > Hi Honghui, Bjorn, > > On Fri, 2017-08-04 at 08:18 -0500, Bjorn Helgaas wrote: > > On Fri, Aug 04, 2017 at 04:39:36PM +0800, Honghui Zhang wrote: > > > On Thu, 2017-08-03 at 17:42 -0500, Bjorn Helgaas wrote: > > > > > + > > > > > +static struct mtk_pcie_port *mtk_pcie_find_port(struct mtk_pcie *pcie, > > > > > + struct pci_bus *bus, int devfn) > > > > > +{ > > > > > + struct pci_dev *dev; > > > > > + struct pci_bus *pbus; > > > > > + struct mtk_pcie_port *port, *tmp; > > > > > + > > > > > + list_for_each_entry_safe(port, tmp, &pcie->ports, list) { > > > > > + if (bus->number == 0 && port->index == PCI_SLOT(devfn)) { > > > > > + return port; > > > > > + } else if (bus->number != 0) { > > > > > + pbus = bus; > > > > > + do { > > > > > + dev = pbus->self; > > > > > + if (port->index == PCI_SLOT(dev->devfn)) > > > > > + return port; > > > > > + pbus = dev->bus; > > > > > + } while (dev->bus->number != 0); > > > > > + } > > > > > + } > > > > > + > > > > > + return NULL; > > > > > > > > You should be able to use sysdata to avoid searching the list. > > > > See drivers/pci/host/pci-aardvark.c, for example. > > > > > > > > > > I could put the mtk_pcie * in sysdata, but still need to searching the > > > list to get the mtk_pcie_port *, how about: > > > > > > list_for_each_entry_safe(port, tmp, &pcie->ports, list) { > > > if (port->index == PCI_SLOT(devfn)) > > > return port; > > > } > > > > No. Other drivers don't need to search the list. Please take a look > > at them and see how they solve this problem. I don't think your > > hardware is fundamentally different in a way that means you need to > > search when the others don't. > > > > I'm not directly involved in this generation, but I guess the main reason why Honghui need to do that is just because this hardware access configuration space via per-port registers, not just for the guard. > Currently, We had a host bridge with two ports (two subnodes in binding text), thus he tried to tells them apart so that he can get the correct registers. > > Some platforms don't need to do that since they just have a single port (no more subnodes), the others might have specific/shared registers to access configuration space. (e.g. Tegra, MTK legacy IP block). > Or, he can split them into two independent nodes, but it will break common probing flow by doing so. (I'd prefer to use subnodes.) > > Ryder > Sorry for the typesetting in previous mail and noise again, I've took a look at pci-rcar-gen2.c, this is a similar case I can found for Honghui's case. It gathers two ports reg regions into one, and uses the "slot id" to calculate the cfg base of each port. Perhaps this is a example for those who need to use subnodes and use port registers for cfg operation. Not sure whether it's worthwhile doing that since we need to changes ports/host structures. Ryder.