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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 7C14BFF6E86 for ; Tue, 17 Mar 2026 21:29:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:References: List-Owner; bh=DODtmRDCwQbpqYyZIoeaGL3yi3GSc6Nf90VRx21d7ic=; b=NScX7x5++o2ENX mM3R/Zw64uGCrFrKhXwDUOXufIqNkpJ4fX/+daCpr1XbhTBQwLWhDLspUV5uMfrJPqEisXLCIrhPy L821lVfpPnRaQs9Aey6PqYjiK9A3KPg5Uz/WTmbdkARRI261LLdd/m+R6lJHwhRQ2gco+/j7P38D/ vqKtC5R5rTTjjFtsc5IP2y50nzF6oIW05V1li00gXM0CQuyQGezB0lXsBrrtyHgWye0bx25GswcPq TyYRjBi2OsXOhTS21EaAkI2CY+8e1R5UlYwlgKWMi6kPko3bHegfimxy2kM8s2OaSp4biWNuX3fyj ExTGmu5P0VAOyB93XwcQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1w2byT-00000007FzS-2lrr; Tue, 17 Mar 2026 21:29:13 +0000 Received: from sea.source.kernel.org ([172.234.252.31]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1w2byR-00000007Fyr-0eW7 for linux-mediatek@lists.infradead.org; Tue, 17 Mar 2026 21:29:12 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id CC9B240106; Tue, 17 Mar 2026 21:29:09 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 81C6EC4CEF7; Tue, 17 Mar 2026 21:29:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773782949; bh=EEPcdwfYA2i1wDNKfSw099Z5veH/DJsStfCV0MN+hNM=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=mNngK0/Fs/0IBKQ6aMEbV8XD37uWZwqxk9Xp1x3CSxJsS/UYuc7J+7WpeXQjIv9ec X8EcEeWKHBjvgKMyu88CqnlBxL2FAWqBgqJ4ozol6/VeGTI5aw1QFR1zLgeXFDVjMj Vh6uui+Fy6IJVUmetrS8GwD0rBJEg8lPlnZn8e78rGdrnEcwsHeuy895dwjCKj/iZe dJo+fNqA/n+fe+zuUf5P+uyUVtuF5G2F5N53qMXibkbEQPNAYVaY1EcNuLb40V7IK+ bTXVtpbv+vjN6Jcthvxlff79woq7ce2WQMs/ChrloY0QQo6VedrOb7moFEJyJlBC9E IM6wbxpicP85A== Date: Tue, 17 Mar 2026 16:29:08 -0500 From: Bjorn Helgaas To: Caleb James DeLisle Cc: linux-pci@vger.kernel.org, linux-mips@vger.kernel.org, naseefkm@gmail.com, ryder.lee@mediatek.com, bhelgaas@google.com, lpieralisi@kernel.org, kwilczynski@kernel.org, mani@kernel.org, robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org, matthias.bgg@gmail.com, angelogioacchino.delregno@collabora.com, ansuelsmth@gmail.com, linux-mediatek@lists.infradead.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 3/3] PCI: Skip bridge window reads when window is not supported Message-ID: <20260317212908.GA109023@bhelgaas> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260316155157.679533-4-cjd@cjdns.fr> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260317_142911_232916_C8C71113 X-CRM114-Status: GOOD ( 18.64 ) X-BeenThere: linux-mediatek@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-mediatek" Errors-To: linux-mediatek-bounces+linux-mediatek=archiver.kernel.org@lists.infradead.org On Mon, Mar 16, 2026 at 03:51:57PM +0000, Caleb James DeLisle wrote: > pci_read_bridge_io() and pci_read_bridge_mmio_pref() read bridge window > registers unconditionally. If the registers are hardwired to zero > (not implemented), both base and limit will be 0. Since (0 <= 0) is > true, a bogus window [mem 0x00000000-0x000fffff] or [io 0x0000-0x0fff] > gets created. > > pci_read_bridge_windows() already detects unsupported windows by > testing register writability and sets io_window/pref_window flags > accordingly. Check these flags at the start of pci_read_bridge_io() > and pci_read_bridge_mmio_pref() to skip reading registers when the > window is not supported. The fundamental problem here is that assigned space to a bridge window that isn't implemented. I wish we understood the connection between this "read window" path and the assignment path. Maybe this patch fixes it because we enter pci_read_bridge_mmio_pref() with res->flags being NULL, and we set IORESOURCE_MEM | IORESOURCE_PREFETCH again, which makes it look like we can assign space for it? If that's the case, I think it would improve the commit log to mention the actual mechanism by which we avoid assigning space. > Suggested-by: Bjorn Helgaas > Link: https://lore.kernel.org/all/20260113210259.GA715789@bhelgaas/ > Signed-off-by: Ahmed Naseef > Signed-off-by: Caleb James DeLisle > --- > drivers/pci/probe.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c > index bccc7a4bdd79..4eacb741b4ec 100644 > --- a/drivers/pci/probe.c > +++ b/drivers/pci/probe.c > @@ -395,6 +395,9 @@ static void pci_read_bridge_io(struct pci_dev *dev, struct resource *res, > unsigned long io_mask, io_granularity, base, limit; > struct pci_bus_region region; > > + if (!dev->io_window) > + return; > + > io_mask = PCI_IO_RANGE_MASK; > io_granularity = 0x1000; > if (dev->io_window_1k) { > @@ -465,6 +468,9 @@ static void pci_read_bridge_mmio_pref(struct pci_dev *dev, struct resource *res, > pci_bus_addr_t base, limit; > struct pci_bus_region region; > > + if (!dev->pref_window) > + return; > + > pci_read_config_word(dev, PCI_PREF_MEMORY_BASE, &mem_base_lo); > pci_read_config_word(dev, PCI_PREF_MEMORY_LIMIT, &mem_limit_lo); > base64 = (mem_base_lo & PCI_PREF_RANGE_MASK) << 16; > -- > 2.39.5 >