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Message-ID: <20210806222151.GA1892781@bjorn-Precision-5520>
Date: Fri, 6 Aug 2021 17:21:51 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Jeremy Linton <jeremy.linton@....com>
Cc: linux-pci@...r.kernel.org, lorenzo.pieralisi@....com,
nsaenz@...nel.org, bhelgaas@...gle.com, rjw@...ysocki.net,
lenb@...nel.org, robh@...nel.org, kw@...ux.com,
f.fainelli@...il.com, bcm-kernel-feedback-list@...adcom.com,
linux-acpi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-rpi-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] PCI: brcmstb: Add ACPI config space quirk
On Thu, Aug 05, 2021 at 04:11:59PM -0500, Jeremy Linton wrote:
> The PFTF CM4 is an ACPI platform that is following the PCIe SMCCC
> standard because its PCIe config space isn't ECAM compliant and is
> split into two parts. One part for the root port registers and a
> moveable window which points at a given device's 4K config space.
> Thus it doesn't have a MCFG (and really any MCFG provided would be
> nonsense anyway). As Linux doesn't support the PCIe SMCCC standard
> we key off a Linux specific host bridge _DSD to add custom ECAM
> ops and cfgres. The cfg op selects between those two regions, as
> well as disallowing problematic accesses, particularly if the link
> is down because there isn't an attached device.
I'm not sure SMCCC is *really* relevant here. If it is, an expansion
of the acronym and a link to a spec would be helpful.
But AFAICT the only important thing here is that it doesn't have
standard ECAM, and we're going to work around that.
I don't see anything about _DSD in this series.
> Signed-off-by: Jeremy Linton <jeremy.linton@....com>
> ---
> drivers/pci/controller/Makefile | 1 +
> drivers/pci/controller/pcie-brcmstb-acpi.c | 77 ++++++++++++++++++++++
> include/linux/pci-ecam.h | 1 +
> 3 files changed, 79 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..76944876155f
> --- /dev/null
> +++ b/drivers/pci/controller/pcie-brcmstb-acpi.c
> @@ -0,0 +1,77 @@
> +// 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 <linux/io.h>
> +#include <linux/pci.h>
> +#include <linux/pci-acpi.h>
Do we use something from pci-acpi.h?
> +#include <linux/pci-ecam.h>
> +#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. This code simply honors the quirk provided base+size
> + * instead.
> + */
> + 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)
Rewrap to fit in 80 columns. 81 is just ... weird :)
> +{
> + 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 */
> + 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;
What happens if the link goes down here? Hopefully that's a
recoverable error?
> + /* 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
>
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