Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936919AbdCJM40 (ORCPT ); Fri, 10 Mar 2017 07:56:26 -0500 Received: from bastet.se.axis.com ([195.60.68.11]:60772 "EHLO bastet.se.axis.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935537AbdCJM4W (ORCPT ); Fri, 10 Mar 2017 07:56:22 -0500 Subject: Re: [RESEND PATCH v3 5/7] PCI: dwc: all: Modify dbi accessors to access data of 4/2/1 bytes To: Kishon Vijay Abraham I , Bjorn Helgaas , Joao Pinto , , , , References: <1489041545-15730-1-git-send-email-kishon@ti.com> <1489041545-15730-6-git-send-email-kishon@ti.com> <58C29648.5020708@ti.com> CC: , Jingoo Han , Richard Zhu , Lucas Stach , Murali Karicheri , Thomas Petazzoni , Jesper Nilsson , Zhou Wang , Gabriele Paoloni From: Niklas Cassel Message-ID: <61f90a03-7164-8e79-f1c2-0ae48b5892a8@axis.com> Date: Fri, 10 Mar 2017 13:56:17 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Icedove/45.6.0 MIME-Version: 1.0 In-Reply-To: <58C29648.5020708@ti.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.0.5.60] X-ClientProxiedBy: XBOX03.axis.com (10.0.5.17) To XBOX02.axis.com (10.0.5.16) X-TM-AS-GCONF: 00 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2107 Lines: 53 On 03/10/2017 01:04 PM, Kishon Vijay Abraham I wrote: > Hi, > > On Thursday 09 March 2017 08:18 PM, Niklas Cassel wrote: >> On 03/09/2017 07:39 AM, Kishon Vijay Abraham I wrote: >>> Previously dbi accessors can be used to access data of size 4 >>> bytes. But there might be situations (like accessing >>> MSI_MESSAGE_CONTROL in order to set/get the number of required >>> MSI interrupts in EP mode) where dbi accessors must >>> be used to access data of size 2. This is in preparation for >>> adding endpoint mode support to designware driver. >> Hello Kishon >> >> I don't really like the idea of adding an extra argument to every existing read/write. >> Will not a read/write of length != 32 be quite uncommon compared to >> a read/write of length == 32? >> >> How about adding some defines to pcie-designware.h: >> >> #define dw_pcie_writel_dbi(pci, base, reg, val) dw_pcie_write_dbi(pci, base, reg, 0x4, val) >> #define dw_pcie_readl_dbi(pci, base, reg) dw_pcie_read_dbi(pci, base, reg, 0x4) >> >> That way we don't have to change every existing read/write. >> >> >> >> Is there a reason why we can't just do: >> >> vial = dw_pcie_readl_dbi(pci, base, MSI_MESSAGE_CONTROL); > MSI_MESSAGE_CONTROL is 0x52 (MSI capability offset + 2). I'm not sure if we can > do a readl that crosses the alignment boundary in all platforms. The other > option is to readl from "MSI capability offset + 0" and extract the last 16 > bits. I felt this is more clear since we are interested only in the > MSI_MESSAGE_CONTROL. > >> >> dw_pcie_writel_dbi(pci, base, MSI_MESSAGE_CONTROL, val); >> >> Or are we going to be doing read/writes of length != 32 so often that >> you think that it's cleaner to have this abstraction? > it's used mainly for accessing configuration space header fields. Even the pci > core uses *pci_read_config_word* for accessing such fields. I see. Adding an extra size argument is a good thing then, since it's consistent with the pci generic code. However, I still think that having defines for writel/readl is a good thing :) > > Thanks > Kishon