From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 116B22AE8D; Tue, 3 Mar 2026 00:03:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772496219; cv=none; b=rShoki2sZUO4y4pO8GcU1hzuAY4uyvbkdORPmHsnKMSFDc0ndZjZG48fscjkRyRa8+Go6OBSrWDZvEALz4WmVN5ZPBE2521swXorb7GhyIroQL90rbisO0tMOmxDnKgVrJewxNLxPeMd2tBmIX2b6a+KeCVxlHDjLDvQtC2H270= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772496219; c=relaxed/simple; bh=4emZIzE+o1mlLRHR+GatVLXIOOg5njXFyaCJc8pf0XE=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; b=jNz7t8c1SbGtxuW69OYaAop/xgexrtKSGMWIqyY3PzpN2Ybvpjcl+Cgq1rfACOPcri0kPcWqw3yPlolx18vlTh+wR8Z+DndHvao1Z2oqynzg7onjlkAJ3QtxskA9LG2WD3LhK+FfyXKQ8n5zd6FBp4ICzpEro0ULC/4jVMpmuAI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=rT7R3VyZ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="rT7R3VyZ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 52271C19423; Tue, 3 Mar 2026 00:03:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1772496218; bh=4emZIzE+o1mlLRHR+GatVLXIOOg5njXFyaCJc8pf0XE=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=rT7R3VyZBPsn1Tn+AKkUHaZkbdt3ESIvze8qu4nTPOUkCpqcFH7Rwn2lYTWZ2RRot lyh1kFyd/nk6onbJJ3pe/rOqrQxHTUj6e9VxyT6yKcy8Pe2tyaYg3X0TpyNqIVxWkP mDQfzDU0OB+QHWACtijiH4cB9YyTeZHJ/BLXC/odqSH/Mq1+ZPvrEZpCOX9KMa62F/ 0n/d2y2UfLGJWfTDmGWR4jINaFdTybaHJ0jXraGt1jyTHgSxJsjeZU3efGUJaPldSc tl4744T6gntm4YbGw7c5iMM/OxYH15RlQ8uCA9wQWp7k9O6KUPNueO78zFdBitj6NF APJtEyQw3eNnQ== Date: Mon, 2 Mar 2026 18:03:37 -0600 From: Bjorn Helgaas To: Jim Quinlan Cc: linux-pci@vger.kernel.org, bcm-kernel-feedback-list@broadcom.com, Bjorn Helgaas , open list , Hans Zhang <18255117159@163.com>, Niklas Cassel Subject: Re: [PATCH v2 RESEND 1/1] PCI: pcie_bus_config can be set at build time Message-ID: <20260303000337.GA4038046@bhelgaas> Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Tue, Feb 24, 2026 at 04:10:17PM -0500, Jim Quinlan wrote: > On Fri, Feb 20, 2026 at 5:11 PM Bjorn Helgaas wrote: > > On Mon, Sep 28, 2020 at 03:46:51PM -0400, Jim Quinlan wrote: > > > The Kconfig is modified so that the pcie_bus_config setting can be done at > > > build time in the same manner as the CONFIG_PCIEASPM_XXXX choice. The > > > pci_bus_config setting may still be overridden by the bootline param. > > > > > > Signed-off-by: Jim Quinlan > > > > We merged this as b0e85c3c8554 ("PCI: Add Kconfig options for MPS/MRRS > > strategy"), which appeared in v5.10. > > > > In retrospect, I think this might have been a mistake because it > > forces a build-time configuration for something that may not be known > > at build time and can be set via command-line parameter. > ... > > But I can't find any discussion about it. Did you have a use case > > where command line parameters weren't usable? > > Yes. We have a Cable Modem (CM) customer who can update their Linux > version but cannot update their boot loader or its default bootline. > FWIW, they only want the option to set pcie_bus_config to > PCIE_BUS_SAFE via the .config. > ... > It's a CM product which uses a particular Wifi chip. Recognizing this > scenario would have the RC trying to grab the EP's vendor-id (and > possibly more info), and that seems awkward at best. This is actually kind of weird. I don't know why a particular device would have any special MPS or MRRS requirements. Do you have any more details about this? Does the WiFi chip actually not *work* with other MPS settings? Or is this a performance thing where other settings don't give acceptable performance? I assume there's no hotplug in this setup, so we don't't have to worry about adding new devices at runtime. Do you know if there's any P2PDMA usage?