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 1A93E55C05; Fri, 19 Jan 2024 17:31:39 +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=1705685500; cv=none; b=u7NZkcTE3BrpOhGH92e7EMtdkW0TTBDqehWpwKvrdzrNMOCBbB7aU8oF2MmN7w64LCfDYNnhUJZtiWMJitIDM+UX83MClA+JgKMGHpLz4ak2yDldhY/yf3br0WUIa4CJMdP/H9Kk6qVRvcXkwjkdq1W+k+KrGnqyNVle04n/Clw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1705685500; c=relaxed/simple; bh=bx3dBEafVwA3lVJVceH0Td6l7zSsuteDOXP4YqQuYQQ=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; b=iQEERUECthgDV8UCBEucyUFsDBFu2J5lIFktbBfo1qYn/Av9KusCpcjtJ/w/N00OY2Ekmc2oQWfx5dBioi2oQLFjWngGvW7Zpto/BNkaQ3qUK2JXPMT8sLKrnH40nDmplUjCChXvEp6p8CFFkBSF2d3rBHxsKHeQucCsnyL1qC0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=d3eVaqJV; 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="d3eVaqJV" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3592AC433F1; Fri, 19 Jan 2024 17:31:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1705685499; bh=bx3dBEafVwA3lVJVceH0Td6l7zSsuteDOXP4YqQuYQQ=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=d3eVaqJVId8F9SFx2HE7+VtBKBkeoTgOSnCfGcnutVGB8Amu2/NnAr53RHpdJW2cI HsrCHES1ME2ZiCgLk6EGJZ08QqQamaNwM/dbaSfc1oas1ONNVAI1XEH7Pp3sMe+nQ6 k4w/PAWIWW0rY38M5L0JQwavF9MGjRS/YOEUv5ktyVRdMAslB6F1gZ3sH0a0qDJ8b3 4K29qSzZG6hn5jyt1VLBc2obJvJVFWAQOwauaeBIZ7MUe7eRZKL0jExT4NydchuIVx SdTIokkHWVIE0KAg0DXmhikeel9INExRR1RqCK0mijGX2qrUNINUVGexcvi5zp43iP w2pZNvgaL6SZw== Date: Fri, 19 Jan 2024 11:31:37 -0600 From: Bjorn Helgaas To: Vidya Sagar Cc: robh@kernel.org, lpieralisi@kernel.org, kw@linux.com, bhelgaas@google.com, krzysztof.kozlowski+dt@linaro.org, conor+dt@kernel.org, will@kernel.org, frowand.list@gmail.com, linux-pci@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, treding@nvidia.com, jonathanh@nvidia.com, kthota@nvidia.com, mmaddireddy@nvidia.com, sagar.tv@gmail.com, kernel test robot Subject: Re: [PATCH V2 2/2] PCI: Add support for "preserve-boot-config" property Message-ID: <20240119173137.GA180921@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=us-ascii Content-Disposition: inline In-Reply-To: <5e8f6c52-6149-42c0-affb-d8b072a77956@nvidia.com> On Mon, Jan 15, 2024 at 08:02:56PM +0530, Vidya Sagar wrote: > On 1/12/2024 10:28 PM, Bjorn Helgaas wrote: > > On Wed, Jan 10, 2024 at 08:37:25AM +0530, Vidya Sagar wrote: > > > Add support for "preserve-boot-config" property that can be used to > > > selectively (i.e. per host bridge) instruct the kernel to preserve the > > > boot time configuration done by the platform firmware. > > > > > > Reported-by: kernel test robot > > > Signed-off-by: Vidya Sagar > > > --- > > > V2: > > > * Addressed issues reported by kernel test robot > > > > > > drivers/pci/controller/pci-host-common.c | 5 ++++- > > > drivers/pci/of.c | 18 ++++++++++++++++++ > > > drivers/pci/probe.c | 2 +- > > > include/linux/of_pci.h | 6 ++++++ > > > 4 files changed, 29 insertions(+), 2 deletions(-) > > > > > > diff --git a/drivers/pci/controller/pci-host-common.c b/drivers/pci/controller/pci-host-common.c > > > index 6be3266cd7b5..d3475dc9ec44 100644 > > > --- a/drivers/pci/controller/pci-host-common.c > > > +++ b/drivers/pci/controller/pci-host-common.c > > > @@ -68,13 +68,16 @@ int pci_host_common_probe(struct platform_device *pdev) > > > > > > of_pci_check_probe_only(); > > > > > > + bridge->preserve_config = > > > + of_pci_check_preserve_boot_config(dev->of_node); > > > > Thanks for leveraging the existing "preserve_config" support for the > > ACPI _DSM. Is pci_host_common_probe() the best place for this? I > > think there are many DT platform drivers that do not use > > pci_host_common_probe(), so I wonder if there's a more generic place > > to put this. > > My understanding is that pci_host_common_probe() is mainly used in > systems where the firmware would have taken care of all the platform > specific initialization and giving the ECAM and 'ranges' info through DT > for the Linux kernel to go ahead and perform the enumeration. This is > similar to ACPI way of handing over the system from firmware to the OS. > > If PCIe controllers are getting initialized in the kernel itself, then > pci_host_probe() is called directly from the respective host controller > drivers which is the case with all the DesignWare based implementations > including Tegra194 and Tegra234. In those systems, since the controllers > themselves have come up and gotten initialized in the kernel, resource > assignment has to happen anyway. acpi_pci_root_create() sets "preserve_config" based on the DSM_PCI_PRESERVE_BOOT_CONFIG _DSM for all ACPI host bridges. Similarly, I think we should set "preserve_config" based on the DT "preserve-boot-config" property for *all* DT-based host bridges, regardless of where the controller init happens. acpi_pci_root_create pci_create_root_bus pci_alloc_host_bridge pci_register_host_bridge acpi_evaluate_dsm_typed(DSM_PCI_PRESERVE_BOOT_CONFIG) <-- pci_scan_child_bus pci_host_common_probe + of_pci_check_preserve_boot_config <-- proposed pci_host_probe pci_scan_root_bus_bridge pci_register_host_bridge pci_set_bus_of_node pci_scan_child_bus Maybe we should do both in pci_register_host_bridge()? E.g., make a function that sets "preserve_config" based on either the ACPI _DSM or the DT property, whichever is appropriate, and call it from pci_register_host_bridge()? Bjorn