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=-16.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,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 7B40BC433E0 for ; Mon, 15 Feb 2021 21:13:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4401A64DE0 for ; Mon, 15 Feb 2021 21:13:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229703AbhBOVNo (ORCPT ); Mon, 15 Feb 2021 16:13:44 -0500 Received: from mail.kernel.org ([198.145.29.99]:57722 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229608AbhBOVNn (ORCPT ); Mon, 15 Feb 2021 16:13:43 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 34A3C64DE0; Mon, 15 Feb 2021 21:13:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1613423582; bh=HKzNmrEZwWl4gA6FiJSt/SCldemDIPw8NQrBl4nmKO0=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=b1FMGpwhpcgdFTlPf+HCZm7lHhQaJuf49Kbaf1cvH9DcYvgu+lJRrtqCe+Yzl2MRr C5ko1HQsnykxLzaFc7P4G2rnz51E6qSxMieoUA31t0Eot8X0KPe7ms7k/kESJBfXr1 cgRcA5IziOqqX7doY2YdwKRYBNf4kcA7+4SBrBmodGjHwkW2DyWtjzRyKMFlDMclXk 4/mmRhtuzv3o6IEUU9bJWLFAzbLgSVZnE3nilbj5CPh7rtn7WZVweLDzKsjO1rIs2e APbIiy0NZCoaGGRV8/fMjN1E+zmeP8dDd9OmYuDGp5XoE6zqj9ZdRa9bi3C9hpyO1s +DIIq398BazOQ== Date: Mon, 15 Feb 2021 15:13:00 -0600 From: Bjorn Helgaas To: Wasim Khan Cc: bhelgaas@google.com, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, Wasim Khan Subject: Re: [PATCH] PCI : check if type 0 devices have all BARs of size zero Message-ID: <20210215211300.GA748236@bjorn-Precision-5520> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210212100856.473415-1-wasim.khan@oss.nxp.com> Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Fri, Feb 12, 2021 at 11:08:56AM +0100, Wasim Khan wrote: > From: Wasim Khan > > Log a message if all BARs of type 0 devices are of > size zero. This can help detecting type 0 devices > not reporting BAR size correctly. I could be missing something, but I don't think we can do this. I would think the simplest possible presilicon testing would find errors like this, and the first attempt to have a driver claim the device would fail if required BARs were missing, so I'm not sure what this would add. While the subject line says "type 0 devices," this code path is also used for type 1 devices (bridges), and it's quite common for bridges to have no BARs, which means they would all be hardwired to zero. It is also legal for even type 0 devices to implement no BARs. They may be operated entirely via config space or via device-specific BARs that are unknown to the PCI core. > Signed-off-by: Wasim Khan > --- > drivers/pci/probe.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c > index 953f15abc850..6438d6d56777 100644 > --- a/drivers/pci/probe.c > +++ b/drivers/pci/probe.c > @@ -321,6 +321,7 @@ int __pci_read_base(struct pci_dev *dev, enum pci_bar_type type, > static void pci_read_bases(struct pci_dev *dev, unsigned int howmany, int rom) > { > unsigned int pos, reg; > + bool found = false; > > if (dev->non_compliant_bars) > return; > @@ -333,8 +334,12 @@ static void pci_read_bases(struct pci_dev *dev, unsigned int howmany, int rom) > struct resource *res = &dev->resource[pos]; > reg = PCI_BASE_ADDRESS_0 + (pos << 2); > pos += __pci_read_base(dev, pci_bar_unknown, res, reg); > + found |= res->flags ? 1 : 0; > } > > + if (!dev->hdr_type && !found) > + pci_info(dev, "BAR size is 0 for BAR[0..%d]\n", howmany - 1); > + > if (rom) { > struct resource *res = &dev->resource[PCI_ROM_RESOURCE]; > dev->rom_base_reg = rom; > -- > 2.25.1 >