From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3C405C433DF for ; Tue, 30 Jun 2020 13:53:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1E400206EB for ; Tue, 30 Jun 2020 13:53:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593525187; bh=DT35ELVgMqJzlhLA7qu4G6VgRNYAREppcPFMWUWIO0M=; h=Date:From:To:Cc:Subject:In-Reply-To:List-ID:From; b=y/CzETCLOAz93koehju7yygy/DAQfLf9dkJ6oIMBCSkUxkzhCd4PFEWBd1T7cgtj5 64J8Kg7TNuwlmFoxilS2V3qfUQeH4/z4lej3fVN/U8QuHC/vdFWaV03dGExe6Pyu43 GFg4dgqkTQzqvbCH6d6lwLFWJ7lV2Aq74sYD6/Yo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388610AbgF3Nwy (ORCPT ); Tue, 30 Jun 2020 09:52:54 -0400 Received: from mail.kernel.org ([198.145.29.99]:40256 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388416AbgF3Nva (ORCPT ); Tue, 30 Jun 2020 09:51:30 -0400 Received: from localhost (mobile-166-175-191-139.mycingular.net [166.175.191.139]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 047A8206BE; Tue, 30 Jun 2020 13:51:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593525089; bh=DT35ELVgMqJzlhLA7qu4G6VgRNYAREppcPFMWUWIO0M=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=kCZGDQTUUI2rEIYfln/G2FtlWnJuHoW3ylN6MmFEOreoxaDbPeX9ZkAIFhOOAY0lU HE/T9DodsxPnfGzgRSOhiH+J2ZyzmkjUFPe1RznrUtTigIsLS0RyD4I6QbQ1AEkbPR 4HMWBIN5v2/s/AG9OekjEZo/C1oFsae9WVFnB69k= Date: Tue, 30 Jun 2020 08:51:27 -0500 From: Bjorn Helgaas To: Pali =?iso-8859-1?Q?Roh=E1r?= Cc: Thomas Petazzoni , Lorenzo Pieralisi , Andrew Murray , Bjorn Helgaas , Marek =?iso-8859-1?Q?Beh=FAn?= , Remi Pommarel , Tomasz Maciej Nowak , Xogium , linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] PCI: aardvark: Don't touch PCIe registers if no card connected Message-ID: <20200630135127.GA3414186@bjorn-Precision-5520> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200528163809.54f5ldvphrjg3zg3@pali> Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Thu, May 28, 2020 at 06:38:09PM +0200, Pali Rohár wrote: > On Thursday 28 May 2020 11:26:04 Bjorn Helgaas wrote: > > On Thu, May 28, 2020 at 04:31:41PM +0200, Pali Rohár wrote: > > > When there is no PCIe card connected and advk_pcie_rd_conf() or > > > advk_pcie_wr_conf() is called for PCI bus which doesn't belong to emulated > > > root bridge, the aardvark driver throws the following error message: > > > > > > advk-pcie d0070000.pcie: config read/write timed out > > > > > > Obviously accessing PCIe registers of disconnected card is not possible. > > > > > > Extend check in advk_pcie_valid_device() function for validating > > > availability of PCIe bus. If PCIe link is down, then the device is marked > > > as Not Found and the driver does not try to access these registers. > > > > > > Signed-off-by: Pali Rohár > > > --- > > > drivers/pci/controller/pci-aardvark.c | 3 +++ > > > 1 file changed, 3 insertions(+) > > > > > > diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c > > > index 90ff291c24f0..53a4cfd7d377 100644 > > > --- a/drivers/pci/controller/pci-aardvark.c > > > +++ b/drivers/pci/controller/pci-aardvark.c > > > @@ -644,6 +644,9 @@ static bool advk_pcie_valid_device(struct advk_pcie *pcie, struct pci_bus *bus, > > > if ((bus->number == pcie->root_bus_nr) && PCI_SLOT(devfn) != 0) > > > return false; > > > > > > + if (bus->number != pcie->root_bus_nr && !advk_pcie_link_up(pcie)) > > > + return false; > > > > I don't think this is the right fix. This makes it racy because the > > link may go down after we call advk_pcie_valid_device() but before we > > perform the config read. > > Yes, it is racy, but I do not think it cause problems. Trying to read > PCIe registers when device is not connected cause just those timeouts, > printing error message and increased delay in advk_pcie_wait_pio() due > to polling loop. This patch reduce unnecessary access to PCIe registers > when advk_pcie_wait_pio() polling just fail. What happens when the device is removed after advk_pcie_link_up() returns true, but before we actually do the config access?