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=-8.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 5D207C433DF for ; Thu, 9 Jul 2020 11:36:32 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 26C0C206DF for ; Thu, 9 Jul 2020 11:36:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="g58HwxDR" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 26C0C206DF Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=zctveL3Ie/wPgqWRfXvYSo052cQxYf9iklPCiZSNyiI=; b=g58HwxDRKufuKObQFsOadOeSh 7w5m1B/LPraHa7Ps59cDtcYF0cHQPHAg6g6qe+vjrkaC6xy4IrJftPxduzndNBsuoD7B6b5wRd795 P04fxNxm0VJ+70w0PSeuje2FU1CW+PTVBFT7iYtjD1QJGWXPVgCiZMtxCdzCi3RK05EF/EXAdMp3R 4DPBU7l1x3T1Fdm/gryXLwLrAb0TJSiqQ6sFZaTGlKr4tJMYByCmFHx1uL4JIzBNt6u/YdrCEeC33 mntlgmXuwXomhWnb3urjM9Z0xUx8h6Rt9mimUmUL7Wgtk5+ue5mXmZwnslk+38Lk7d8ze6GIB8QU5 0bFIds+0A==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jtUpi-0007Y5-4p; Thu, 09 Jul 2020 11:35:18 +0000 Received: from foss.arm.com ([217.140.110.172]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jtUpf-0007XI-73 for linux-arm-kernel@lists.infradead.org; Thu, 09 Jul 2020 11:35:16 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id C18D21FB; Thu, 9 Jul 2020 04:35:12 -0700 (PDT) Received: from e121166-lin.cambridge.arm.com (e121166-lin.cambridge.arm.com [10.1.196.255]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 53A4F3F7D7; Thu, 9 Jul 2020 04:35:11 -0700 (PDT) Date: Thu, 9 Jul 2020 12:35:09 +0100 From: Lorenzo Pieralisi To: Pali =?iso-8859-1?Q?Roh=E1r?= Subject: Re: [PATCH v3] PCI: aardvark: Don't touch PCIe registers if no card connected Message-ID: <20200709113509.GB19638@e121166-lin.cambridge.arm.com> References: <20200528143141.29956-1-pali@kernel.org> <20200702083036.12230-1-pali@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200702083036.12230-1-pali@kernel.org> User-Agent: Mutt/1.9.4 (2018-02-28) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200709_073515_317538_30BFD3E4 X-CRM114-Status: GOOD ( 25.18 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Tomasz Maciej Nowak , linux-pci@vger.kernel.org, Xogium , linux-kernel@vger.kernel.org, Marek =?iso-8859-1?Q?Beh=FAn?= , Remi Pommarel , Thomas Petazzoni , Bjorn Helgaas , linux-arm-kernel@lists.infradead.org, Andrew Murray Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Jul 02, 2020 at 10:30:36AM +0200, Pali Roh=E1r 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. > = > This is just an optimization to prevent accessing PCIe registers when card > is disconnected. Trying to access PCIe registers of disconnected card does > not cause any crash, kernel just needs to wait for a timeout. So if card > disappear immediately after checking for PCIe link (before accessing PCIe > registers), it does not cause any problems. > = > Signed-off-by: Pali Roh=E1r > = > --- > Changes in V3: > * Add comment to the code > Changes in V2: > * Update commit message, mention that this is optimization > --- > drivers/pci/controller/pci-aardvark.c | 7 +++++++ > 1 file changed, 7 insertions(+) > = > diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controll= er/pci-aardvark.c > index 90ff291c24f0..d18f389b36a1 100644 > --- a/drivers/pci/controller/pci-aardvark.c > +++ b/drivers/pci/controller/pci-aardvark.c > @@ -644,6 +644,13 @@ static bool advk_pcie_valid_device(struct advk_pcie = *pcie, struct pci_bus *bus, > if ((bus->number =3D=3D pcie->root_bus_nr) && PCI_SLOT(devfn) !=3D 0) > return false; > = > + /* > + * If the link goes down after we check for link-up, nothing bad > + * happens but the config access times out. > + */ > + if (bus->number !=3D pcie->root_bus_nr && !advk_pcie_link_up(pcie)) > + return false; > + > return true; > } Question: this basically means that you can only effectively enumerate bus number =3D=3D root_bus_nr and AFAICS if at probe the link did not come up it will never do, will it ? Isn't this equivalent to limiting the bus numbers the bridge is capable of handling ? Reworded: if in advk_pcie_setup_hw() the link does not come up, what's the point of trying to enumerate the bus hierarchy below the root bus ? Thanks, Lorenzo _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel