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=-8.6 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,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 A8697C433E0 for ; Thu, 28 May 2020 16:38:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 82A0B2089D for ; Thu, 28 May 2020 16:38:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590683896; bh=rYOzZYw6qVcWw1+Bgcj/D7ePhlH1Yu7bCEXs98o9kyQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=G0Url6bi/zP+do1MgoRhtFLkDP6ffe6xLNd3umSXkso7ZVkqGOEhRKAH9ODpU606l Ao4Gun03HSo24qgkmHdOxfkG6m/gkcPthLDc9PYzE63R5M/9hERTBBN1A5kOETRy/X H2dNwLnog3LT28MGhZYWCSe6kmmhSRNW65fZLciw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2405079AbgE1QiN (ORCPT ); Thu, 28 May 2020 12:38:13 -0400 Received: from mail.kernel.org ([198.145.29.99]:40366 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2405066AbgE1QiM (ORCPT ); Thu, 28 May 2020 12:38:12 -0400 Received: from pali.im (pali.im [31.31.79.79]) (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 C30A1207F5; Thu, 28 May 2020 16:38:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590683891; bh=rYOzZYw6qVcWw1+Bgcj/D7ePhlH1Yu7bCEXs98o9kyQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=KM4GsGGiBme8F3C1xykXFeOmV5RsIvJclB1FhdnudGbtu6HE7QAttcQ9C9wzj09yO UquC0s0Yti69s9yLYQ7Ii2DKASs4aCyPR4iyHiiSBUCsc1wgoCd6WcXVh1xiKkEWe+ rHtIXrxYPUbQszvc85RV9TksBsRhjb9YRRZSzF/g= Received: by pali.im (Postfix) id 6CB79865; Thu, 28 May 2020 18:38:09 +0200 (CEST) Date: Thu, 28 May 2020 18:38:09 +0200 From: Pali =?utf-8?B?Um9ow6Fy?= To: Bjorn Helgaas Cc: Thomas Petazzoni , Lorenzo Pieralisi , Andrew Murray , Bjorn Helgaas , Marek =?utf-8?B?QmVow7pu?= , 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: <20200528163809.54f5ldvphrjg3zg3@pali> References: <20200528143141.29956-1-pali@kernel.org> <20200528162604.GA323482@bjorn-Precision-5520> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200528162604.GA323482@bjorn-Precision-5520> User-Agent: NeoMutt/20180716 Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org 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. I think it is a good idea to not call blocking advk_pcie_wait_pio() when it is not needed. We could have faster enumeration of PCIe buses when card is not connected. > I have no objection to removing the "config read/write timed out" > message. The "return PCIBIOS_SET_FAILED" in the read case probably > should be augmented by setting "*val = 0xffffffff". > > > return true; > > } > > > > -- > > 2.20.1 > >