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=-16.7 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,URIBL_BLOCKED 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 E61D6C4320A for ; Fri, 20 Aug 2021 19:06:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D10246112E for ; Fri, 20 Aug 2021 19:06:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234323AbhHTTGp (ORCPT ); Fri, 20 Aug 2021 15:06:45 -0400 Received: from mail.kernel.org ([198.145.29.99]:56170 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230470AbhHTTGo (ORCPT ); Fri, 20 Aug 2021 15:06:44 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 2FD686103D; Fri, 20 Aug 2021 19:06:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1629486366; bh=TpoOerzzSvyAyVWFS5kovs264Ailoo6WpJoiJ6bsflk=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=omh2GmvKul9EnyGAzx1SgUzfiPPdnyinBwaQ0d2tvU3213vCjbHqbSh2UBT5XtbWx klaTwlMT34H89Hk65RDW5i1xdxuspUZIE+W9jGCJhGMbUdUb/VGUkiFOdpHfUCzm91 3qpET7DkQ+AK4LqvdV1YXjK5cw8yer9DYKwWbFH3IHMMuSirCwybFDPs0BnM4qtrlb NR0p0wALitQ3pHm9dF7JlO4C7mK9193EyYVARQ0IXdmHGtqUO8+xPdZkZp5KZHFQfK CHf8gVrcwOSYpwzYPVgG/L0/tGO0jW744qmk6z6NPM/yD3GciRYIll9GBJ16/agb5X HAaAUl/EwaMQQ== Date: Fri, 20 Aug 2021 14:06:04 -0500 From: Bjorn Helgaas To: Jeremy Linton 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, sdonthineni@nvidia.com, stefan.wahren@i2se.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 Subject: Re: [PATCH v2 2/4] PCI: brcmstb: Add ACPI config space quirk Message-ID: <20210820190604.GA3340361@bjorn-Precision-5520> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210819215655.84866-3-jeremy.linton@arm.com> Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Thu, Aug 19, 2021 at 04:56:53PM -0500, Jeremy Linton wrote: > The PFTF CM4 is an ACPI platform that isn't ECAM compliant. Its config > space is in two parts. One part is for the root port registers and a > second moveable window pointing at a device's 4K config space. Thus it > doesn't have an MCFG, and any MCFG provided would be nonsense > anyway. Instead, a Linux specific host bridge _DSD selects a custom > ECAM ops and cfgres. The cfg op picks between those two regions while > disallowing problematic accesses. This doesn't actually say what this patch *does*. Can you expand "PFTF CM4" somehow? Google (and the comment below, I guess) suggests it's something to do with Raspberry Pi 4, but it would be nice if the commit log made sense without Googling or reading the patch. > Signed-off-by: Jeremy Linton > --- > drivers/pci/controller/Makefile | 1 + > drivers/pci/controller/pcie-brcmstb-acpi.c | 74 ++++++++++++++++++++++ > include/linux/pci-ecam.h | 1 + > 3 files changed, 76 insertions(+) > create mode 100644 drivers/pci/controller/pcie-brcmstb-acpi.c > > diff --git a/drivers/pci/controller/Makefile b/drivers/pci/controller/Makefile > index aaf30b3dcc14..65aa6fd3ed89 100644 > --- a/drivers/pci/controller/Makefile > +++ b/drivers/pci/controller/Makefile > @@ -57,5 +57,6 @@ ifdef CONFIG_PCI_QUIRKS > obj-$(CONFIG_ARM64) += pci-thunder-ecam.o > obj-$(CONFIG_ARM64) += pci-thunder-pem.o > obj-$(CONFIG_ARM64) += pci-xgene.o > +obj-$(CONFIG_ARM64) += pcie-brcmstb-acpi.o > endif > endif > diff --git a/drivers/pci/controller/pcie-brcmstb-acpi.c b/drivers/pci/controller/pcie-brcmstb-acpi.c > new file mode 100644 > index 000000000000..71f6def3074c > --- /dev/null > +++ b/drivers/pci/controller/pcie-brcmstb-acpi.c > @@ -0,0 +1,74 @@ > +// SPDX-License-Identifier: GPL-2.0+ > +/* > + * ACPI quirks for Brcm2711 PCIe host controller > + * As used on the Raspberry Pi Compute Module 4 > + * > + * Copyright (C) 2021 Arm Ltd. > + */ > + > +#include > +#include > +#include > +#include "../pci.h" > +#include "pcie-brcmstb.h" > + > +static int brcm_acpi_init(struct pci_config_window *cfg) > +{ > + /* > + * This platform doesn't technically have anything that could be called > + * ECAM. Its config region has root port specific registers between > + * standard PCIe defined config registers. Thus the region setup by the > + * generic ECAM code needs to be adjusted. The HW can access bus 0-ff > + * but the footprint isn't a nice power of 2 (40k). For purposes of > + * mapping the config region we are just going to squash the standard > + * and nonstandard registers together rather than mapping them separately. > + */ > + iounmap(cfg->win); > + cfg->win = pci_remap_cfgspace(cfg->res.start, resource_size(&cfg->res)); > + if (!cfg->win) > + goto err_exit; > + > + /* MSI is nonstandard as well */ > + pci_no_msi(); > + > + return 0; > +err_exit: > + dev_err(cfg->parent, "PCI: Failed to remap config\n"); > + return -ENOMEM; > +} > + > +static void __iomem *brcm_pcie_map_conf2(struct pci_bus *bus, > + unsigned int devfn, int where) > +{ > + struct pci_config_window *cfg = bus->sysdata; > + void __iomem *base = cfg->win; > + int idx; > + u32 up; > + > + /* Accesses to the RC go right to the RC registers if slot==0 */ > + if (pci_is_root_bus(bus)) > + return PCI_SLOT(devfn) ? NULL : base + where; > + > + /* Assure link up before sending request */ Obviously this is horribly racy, since the link may go down after you check but before you send the request. Maybe the hardware leaves you no choice. I'd feel a little better about it if the comment acknowledged that (if it's so) and outlined the consequence of losing the race (panic, recoverable error, etc). > + up = readl(base + PCIE_MISC_PCIE_STATUS); > + if (!(up & PCIE_MISC_PCIE_STATUS_PCIE_DL_ACTIVE_MASK)) > + return NULL; > + > + if (!(up & PCIE_MISC_PCIE_STATUS_PCIE_PHYLINKUP_MASK)) > + return NULL; > + > + /* For devices, write to the config space index register */ > + idx = PCIE_ECAM_OFFSET(bus->number, devfn, 0); > + writel(idx, base + PCIE_EXT_CFG_INDEX); > + return base + PCIE_EXT_CFG_DATA + where; > +} > + > +const struct pci_ecam_ops bcm2711_pcie_ops = { > + .init = brcm_acpi_init, > + .bus_shift = 1, > + .pci_ops = { > + .map_bus = brcm_pcie_map_conf2, > + .read = pci_generic_config_read, > + .write = pci_generic_config_write, > + } > +}; > diff --git a/include/linux/pci-ecam.h b/include/linux/pci-ecam.h > index adea5a4771cf..a5de0285bb7f 100644 > --- a/include/linux/pci-ecam.h > +++ b/include/linux/pci-ecam.h > @@ -87,6 +87,7 @@ extern const struct pci_ecam_ops xgene_v1_pcie_ecam_ops; /* APM X-Gene PCIe v1 * > extern const struct pci_ecam_ops xgene_v2_pcie_ecam_ops; /* APM X-Gene PCIe v2.x */ > extern const struct pci_ecam_ops al_pcie_ops; /* Amazon Annapurna Labs PCIe */ > extern const struct pci_ecam_ops tegra194_pcie_ops; /* Tegra194 PCIe */ > +extern const struct pci_ecam_ops bcm2711_pcie_ops; /* Bcm2711 PCIe */ > #endif > > #if IS_ENABLED(CONFIG_PCI_HOST_COMMON) > -- > 2.31.1 >