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Date:	Tue, 16 Sep 2014 17:23:30 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Jiang Liu <jiang.liu@...ux.intel.com>
Cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Randy Dunlap <rdunlap@...radead.org>,
	Yinghai Lu <yinghai@...nel.org>,
	Borislav Petkov <bp@...en8.de>,
	Grant Likely <grant.likely@...aro.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tony Luck <tony.luck@...el.com>,
	Joerg Roedel <joro@...tes.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	x86@...nel.org, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-acpi@...r.kernel.org
Subject: Re: [Patch v5 05/15] PCI: Remove PCI ioapic driver

On Thu, Sep 11, 2014 at 04:05:48PM +0800, Jiang Liu wrote:
> To support IOAPIC hotplug on x86 and IA64 platforms, OS needs to figure
> out global interrupt source number(GSI) and IOAPIC enumeration ID
> through ACPI interfaces. So BIOS must implement an ACPI IOAPIC device
> with _GSB/_UID or _MAT method to support IOAPIC hotplug. OS also needs
> to figure out base physical address to access IOAPIC registers. OS may
> get the base physical address through PCI BARs if IOAPIC device is
> visible in PCI domain, otherwise OS may get the address by ACPI _CRS
> method if IOAPIC device is hidden from PCI domain by BIOS.
> 
> When adding a PCI subtree, we need to add IOAPIC devices before enabling
> all other PCI devices because other PCI devices may use the IOAPIC to
> allocate PCI interrupts.
> 
> So we plan to reimplement IOAPIC driver as an ACPI instead of PCI driver
> due to:
> 1) hot-pluggable IOAPIC devices are always visible in ACPI domain,
>    but may or may not be visible in PCI domain.
> 2) we could explicitly control the order between IOAPIC and other PCI
>    devices.
> 
> We also have another choice to use a PCI driver to manage IOAPIC device
> if it's visible in PCI domain and use an ACPI driver if it's only
> visible in ACPI domain. But this solution is a little complex.
> 
> It shouldn't cause serious backward compatibility issues because:
> 1) IOAPIC hotplug is never supported on x86 yet because it hasn't
>    implemented the required acpi_register_ioapic() and
>    acpi_unregister_ioapic().
> 2) Currently only ACPI based IOAPIC hotplug is possible on x86 and
>    IA64, we don't know other specifications and interfaces to support
>    IOAPIC hotplug yet.
> 3) We will reimplement an ACPI IOAPICď˝”driver support IOAPIC hotplug.
> 
> This change also helps to get rid of the false alarm on all current
> Linux distributions:
> [    6.952497] ioapic: probe of 0000:00:05.4 failed with error -22
> [    6.959542] ioapic: probe of 0000:80:05.4 failed with error -22
> 
> Signed-off-by: Jiang Liu <jiang.liu@...ux.intel.com>

Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>

I assume this will be merged with the rest of the series, through a non-PCI
tree.

> ---
>  drivers/pci/Kconfig  |    7 ---
>  drivers/pci/Makefile |    2 -
>  drivers/pci/ioapic.c |  121 --------------------------------------------------
>  3 files changed, 130 deletions(-)
>  delete mode 100644 drivers/pci/ioapic.c
> 
> diff --git a/drivers/pci/Kconfig b/drivers/pci/Kconfig
> index 893503fa1782..39866d18004e 100644
> --- a/drivers/pci/Kconfig
> +++ b/drivers/pci/Kconfig
> @@ -104,13 +104,6 @@ config PCI_PASID
>  
>  	  If unsure, say N.
>  
> -config PCI_IOAPIC
> -	bool "PCI IO-APIC hotplug support" if X86
> -	depends on PCI
> -	depends on ACPI
> -	depends on X86_IO_APIC
> -	default !X86
> -
>  config PCI_LABEL
>  	def_bool y if (DMI || ACPI)
>  	select NLS
> diff --git a/drivers/pci/Makefile b/drivers/pci/Makefile
> index e04fe2d9df3b..73e4af400a5a 100644
> --- a/drivers/pci/Makefile
> +++ b/drivers/pci/Makefile
> @@ -13,8 +13,6 @@ obj-$(CONFIG_PCI_QUIRKS) += quirks.o
>  # Build PCI Express stuff if needed
>  obj-$(CONFIG_PCIEPORTBUS) += pcie/
>  
> -obj-$(CONFIG_PCI_IOAPIC) += ioapic.o
> -
>  # Build the PCI Hotplug drivers if we were asked to
>  obj-$(CONFIG_HOTPLUG_PCI) += hotplug/
>  ifdef CONFIG_HOTPLUG_PCI
> diff --git a/drivers/pci/ioapic.c b/drivers/pci/ioapic.c
> deleted file mode 100644
> index f6219d36227f..000000000000
> --- a/drivers/pci/ioapic.c
> +++ /dev/null
> @@ -1,121 +0,0 @@
> -/*
> - * IOAPIC/IOxAPIC/IOSAPIC driver
> - *
> - * Copyright (C) 2009 Fujitsu Limited.
> - * (c) Copyright 2009 Hewlett-Packard Development Company, L.P.
> - *
> - * This program is free software; you can redistribute it and/or modify
> - * it under the terms of the GNU General Public License version 2 as
> - * published by the Free Software Foundation.
> - */
> -
> -/*
> - * This driver manages PCI I/O APICs added by hotplug after boot.  We try to
> - * claim all I/O APIC PCI devices, but those present at boot were registered
> - * when we parsed the ACPI MADT, so we'll fail when we try to re-register
> - * them.
> - */
> -
> -#include <linux/pci.h>
> -#include <linux/module.h>
> -#include <linux/acpi.h>
> -#include <linux/slab.h>
> -
> -struct ioapic {
> -	acpi_handle	handle;
> -	u32		gsi_base;
> -};
> -
> -static int ioapic_probe(struct pci_dev *dev, const struct pci_device_id *ent)
> -{
> -	acpi_handle handle;
> -	acpi_status status;
> -	unsigned long long gsb;
> -	struct ioapic *ioapic;
> -	int ret;
> -	char *type;
> -	struct resource *res;
> -
> -	handle = ACPI_HANDLE(&dev->dev);
> -	if (!handle)
> -		return -EINVAL;
> -
> -	status = acpi_evaluate_integer(handle, "_GSB", NULL, &gsb);
> -	if (ACPI_FAILURE(status))
> -		return -EINVAL;
> -
> -	/*
> -	 * The previous code in acpiphp evaluated _MAT if _GSB failed, but
> -	 * ACPI spec 4.0 sec 6.2.2 requires _GSB for hot-pluggable I/O APICs.
> -	 */
> -
> -	ioapic = kzalloc(sizeof(*ioapic), GFP_KERNEL);
> -	if (!ioapic)
> -		return -ENOMEM;
> -
> -	ioapic->handle = handle;
> -	ioapic->gsi_base = (u32) gsb;
> -
> -	if (dev->class == PCI_CLASS_SYSTEM_PIC_IOAPIC)
> -		type = "IOAPIC";
> -	else
> -		type = "IOxAPIC";
> -
> -	ret = pci_enable_device(dev);
> -	if (ret < 0)
> -		goto exit_free;
> -
> -	pci_set_master(dev);
> -
> -	if (pci_request_region(dev, 0, type))
> -		goto exit_disable;
> -
> -	res = &dev->resource[0];
> -	if (acpi_register_ioapic(ioapic->handle, res->start, ioapic->gsi_base))
> -		goto exit_release;
> -
> -	pci_set_drvdata(dev, ioapic);
> -	dev_info(&dev->dev, "%s at %pR, GSI %u\n", type, res, ioapic->gsi_base);
> -	return 0;
> -
> -exit_release:
> -	pci_release_region(dev, 0);
> -exit_disable:
> -	pci_disable_device(dev);
> -exit_free:
> -	kfree(ioapic);
> -	return -ENODEV;
> -}
> -
> -static void ioapic_remove(struct pci_dev *dev)
> -{
> -	struct ioapic *ioapic = pci_get_drvdata(dev);
> -
> -	acpi_unregister_ioapic(ioapic->handle, ioapic->gsi_base);
> -	pci_release_region(dev, 0);
> -	pci_disable_device(dev);
> -	kfree(ioapic);
> -}
> -
> -
> -static const struct pci_device_id ioapic_devices[] = {
> -	{ PCI_DEVICE_CLASS(PCI_CLASS_SYSTEM_PIC_IOAPIC, ~0) },
> -	{ PCI_DEVICE_CLASS(PCI_CLASS_SYSTEM_PIC_IOXAPIC, ~0) },
> -	{ }
> -};
> -MODULE_DEVICE_TABLE(pci, ioapic_devices);
> -
> -static struct pci_driver ioapic_driver = {
> -	.name		= "ioapic",
> -	.id_table	= ioapic_devices,
> -	.probe		= ioapic_probe,
> -	.remove		= ioapic_remove,
> -};
> -
> -static int __init ioapic_init(void)
> -{
> -	return pci_register_driver(&ioapic_driver);
> -}
> -module_init(ioapic_init);
> -
> -MODULE_LICENSE("GPL");
> -- 
> 1.7.10.4
> 
--
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