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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C6E87C433F5 for ; Tue, 5 Oct 2021 15:44:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A8C4361131 for ; Tue, 5 Oct 2021 15:44:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235992AbhJEPpy (ORCPT ); Tue, 5 Oct 2021 11:45:54 -0400 Received: from foss.arm.com ([217.140.110.172]:34602 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231513AbhJEPpw (ORCPT ); Tue, 5 Oct 2021 11:45:52 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id F27E21FB; Tue, 5 Oct 2021 08:44:01 -0700 (PDT) Received: from [192.168.122.166] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1B48B3F70D; Tue, 5 Oct 2021 08:44:01 -0700 (PDT) Subject: Re: [PATCH v3 3/4] PCI/ACPI: Add Broadcom bcm2711 MCFG quirk To: Bjorn Helgaas Cc: linux-pci@vger.kernel.org, lorenzo.pieralisi@arm.com, nsaenz@kernel.org, bhelgaas@google.com, rjw@rjwysocki.net, lenb@kernel.org, robh@kernel.org, kw@linux.com, f.fainelli@gmail.com, bcm-kernel-feedback-list@broadcom.com, linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-rpi-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <20211005151042.GA1083482@bhelgaas> From: Jeremy Linton Message-ID: <2bcc69b5-6659-0ec4-cd33-a9b8e61d1afe@arm.com> Date: Tue, 5 Oct 2021 10:43:32 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: <20211005151042.GA1083482@bhelgaas> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Thanks for looking at this again. On 10/5/21 10:10 AM, Bjorn Helgaas wrote: > On Thu, Aug 26, 2021 at 02:15:56AM -0500, Jeremy Linton wrote: >> Now that there is a bcm2711 quirk, it needs to be enabled when the >> MCFG is missing. Use an ACPI namespace _DSD property >> "linux-ecam-quirk-id" as an alternative to the MCFG OEM. >> >> Signed-off-by: Jeremy Linton >> Acked-by: Florian Fainelli >> Acked-by: Bjorn Helgaas >> --- >> drivers/acpi/pci_mcfg.c | 17 +++++++++++++++++ >> 1 file changed, 17 insertions(+) >> >> diff --git a/drivers/acpi/pci_mcfg.c b/drivers/acpi/pci_mcfg.c >> index 53cab975f612..04c517418365 100644 >> --- a/drivers/acpi/pci_mcfg.c >> +++ b/drivers/acpi/pci_mcfg.c >> @@ -169,6 +169,9 @@ static struct mcfg_fixup mcfg_quirks[] = { >> ALTRA_ECAM_QUIRK(1, 13), >> ALTRA_ECAM_QUIRK(1, 14), >> ALTRA_ECAM_QUIRK(1, 15), >> + >> + { "bc2711", "", 0, 0, MCFG_BUS_ANY, &bcm2711_pcie_ops, >> + DEFINE_RES_MEM(0xFD500000, 0xA000) }, >> }; >> >> static char mcfg_oem_id[ACPI_OEM_ID_SIZE]; >> @@ -198,8 +201,22 @@ static void pci_mcfg_apply_quirks(struct acpi_pci_root *root, >> u16 segment = root->segment; >> struct resource *bus_range = &root->secondary; >> struct mcfg_fixup *f; >> + const char *soc; >> int i; >> >> + /* >> + * This may be a machine with a PCI/SMC conduit, which means it doesn't >> + * have an MCFG. Use an ACPI namespace definition instead. >> + */ >> + if (!fwnode_property_read_string(acpi_fwnode_handle(root->device), >> + "linux-ecam-quirk-id", &soc)) { >> + if (strlen(soc) != ACPI_OEM_ID_SIZE) > > From a reviewing perspective, it's not obvious why soc must be exactly > ACPI_OEM_ID_SIZE. Does that imply space-padding in the DT string or > something? This is at the moment an ACPI only DSD, and it must follow the MADT OEM_ID format for now because we are effectively just overriding that field. The rest of the code in this module is just treating it as a fixed 6 bytes. > > Is there any documentation for this DT property? Its not a DT property, and its unclear since its linux only if it belongs in previously linked ACPI registry. > > Also not obvious why strlen() is safe here. I mean, I looked a couple > levels deep in fwnode_property_read_string(), but whatever guarantees > null termination is buried pretty deep. I've not tracked down who, if anyone other than the AML compiler is guaranteeing a null. The spec says something to the effect "Most other string, however, are of variable-length and are automatically null terminated by the compiler". Not sure if that helps any. > > It seems a little weird to use an MCFG quirk mechanism when there's no > MCFG at all on this platform. Well its just a point to hook in a CFG space quirk, and since that is what most of the MCFG quirks are, it seemed reasonable to reuse it rather than recreate it. PS, had some offline convo about reposing with a simple rebase and the ACK's applied, will do that if it helps any, but when I checked a couple weeks back this applied to 5.15 automatically. > >> + dev_err(&root->device->dev, "ECAM quirk should be %d characters\n", >> + ACPI_OEM_ID_SIZE); >> + else >> + memcpy(mcfg_oem_id, soc, ACPI_OEM_ID_SIZE); >> + } >> + >> for (i = 0, f = mcfg_quirks; i < ARRAY_SIZE(mcfg_quirks); i++, f++) { >> if (pci_mcfg_quirk_matches(f, segment, bus_range)) { >> if (f->cfgres.start) >> -- >> 2.31.1 >>