Message-ID: <20151217211120.GC29500@localhost>
Date:	Thu, 17 Dec 2015 15:11:20 -0600
From:	Bjorn Helgaas <helgaas@...nel.org>
To:	Joao Pinto <Joao.Pinto@...opsys.com>
Cc:	Vineet.Gupta1@...opsys.com, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, CARLOS.PALMINHA@...opsys.com,
	Alexey.Brodkin@...opsys.com, robh+dt@...nel.org,
	pawel.moll@....com, mark.rutland@....com,
	ijc+devicetree@...lion.org.uk, galak@...eaurora.org
Subject: Re: [PATCH v2 1/2] PCI support added to ARC

On Wed, Dec 16, 2015 at 02:14:55PM +0000, Joao Pinto wrote:
> This patch adds PCI support to ARC and updates drivers/pci Makefile enabling
> the ARC arch to use the generic PCI setup functions.
> 
> Signed-off-by: Joao Pinto <jpinto@...opsys.com>

Checkpatch complains about some whitespace errors (new blank lines at
EOF).

Hmmm, almost all of this appears to be copied straight from arch/arm,
but almost none of it is actually used.  If that's true, it's good
because you can make the patches much smaller.  But it's a little bit
bad, too, because it means we almost merged a bunch of dead code.

> ---
> Change v1 -> v2:
> - In arch/arc/Kconfig, the new menu entry (Bus Configuration) was moved to the
> slot between sourcing of drivers/Kconfig and fs/Kconfig (Vineet Gupta)
> - In arch/arc/plat-axs10x/Kconfig the "select MIGHT_HAVE_PCI" option was placed
> in order as suggested (Vineet Gupta)
> - ioport_map() and ioport_unmap() were static inlined and included in
> the io.h (Vineet Gupta)
> - pcibios_min_io and pcibios_min_mem declaration moved to
> pcibios.c (Vineet Gupta)
> - pr_err() replaced by dev_err() in pcibios_enable_device() (Bjorn Helgaas)
> - string simplified in pcibios_enable_device() (Vineet Gupta)
> - pci_host_bridge_window structure was replaced by resource_entry structure, and
> list_for_each_entry() for resource_list_for_each_entry() in pcibios.c
> 
>  arch/arc/Kconfig                |  23 +++
>  arch/arc/include/asm/dma.h      |   5 +
>  arch/arc/include/asm/io.h       |  10 ++
>  arch/arc/include/asm/mach/pci.h |  97 +++++++++++
>  arch/arc/include/asm/pci.h      |  34 ++++
>  arch/arc/kernel/Makefile        |   1 +
>  arch/arc/kernel/pcibios.c       | 358 ++++++++++++++++++++++++++++++++++++++++
>  arch/arc/mm/ioremap.c           |  10 +-
>  arch/arc/plat-axs10x/Kconfig    |   1 +
>  drivers/pci/Makefile            |   1 +
>  10 files changed, 539 insertions(+), 1 deletion(-)
>  create mode 100644 arch/arc/include/asm/mach/pci.h
>  create mode 100644 arch/arc/include/asm/pci.h
>  create mode 100644 arch/arc/kernel/pcibios.c
> 
> diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
> index 2c2ac3f..98b32c1 100644
> --- a/arch/arc/Kconfig
> +++ b/arch/arc/Kconfig
> @@ -19,6 +19,7 @@ config ARC
>  	select GENERIC_FIND_FIRST_BIT
>  	# for now, we don't need GENERIC_IRQ_PROBE, CONFIG_GENERIC_IRQ_CHIP
>  	select GENERIC_IRQ_SHOW
> +	select GENERIC_PCI_IOMAP
>  	select GENERIC_PENDING_IRQ if SMP
>  	select GENERIC_SMP_IDLE_THREAD
>  	select HAVE_ARCH_KGDB
> @@ -39,6 +40,9 @@ config ARC
>  	select PERF_USE_VMALLOC
>  	select HAVE_DEBUG_STACKOVERFLOW
>  
> +config MIGHT_HAVE_PCI
> +	bool
> +
>  config TRACE_IRQFLAGS_SUPPORT
>  	def_bool y
>  
> @@ -570,6 +574,25 @@ endmenu	 # "ARC Architecture Configuration"
>  source "mm/Kconfig"
>  source "net/Kconfig"
>  source "drivers/Kconfig"
> +
> +menu "Bus Support"
> +
> +config PCI
> +	bool "PCI support" if MIGHT_HAVE_PCI
> +	help
> +	  PCI is the name of a bus system, i.e. the way the CPU talks to the other stuff inside
> +	  your box.Find out if your board/platform have PCI.
> +	  Note: PCIE support for Synopsys Device will be available only when
> +	  HAPS DX is configured with PCIE RC bitmap. If you have PCI, say Y, otherwise N.
> +
> +config PCI_SYSCALL
> +	def_bool PCI
> +
> +source "drivers/pci/Kconfig"
> +source "drivers/pci/pcie/Kconfig"
> +
> +endmenu
> +
>  source "fs/Kconfig"
>  source "arch/arc/Kconfig.debug"
>  source "security/Kconfig"
> diff --git a/arch/arc/include/asm/dma.h b/arch/arc/include/asm/dma.h
> index ca7c451..37942fa 100644
> --- a/arch/arc/include/asm/dma.h
> +++ b/arch/arc/include/asm/dma.h
> @@ -10,5 +10,10 @@
>  #define ASM_ARC_DMA_H
>  
>  #define MAX_DMA_ADDRESS 0xC0000000
> +#ifdef CONFIG_PCI
> +extern int isa_dma_bridge_buggy;
> +#else
> +#define isa_dma_bridge_buggy    (0)
> +#endif
>  
>  #endif
> diff --git a/arch/arc/include/asm/io.h b/arch/arc/include/asm/io.h
> index 694ece8..2ec3cf4 100644
> --- a/arch/arc/include/asm/io.h
> +++ b/arch/arc/include/asm/io.h
> @@ -16,7 +16,17 @@
>  extern void __iomem *ioremap(unsigned long physaddr, unsigned long size);
>  extern void __iomem *ioremap_prot(phys_addr_t offset, unsigned long size,
>  				  unsigned long flags);
> +static inline void __iomem *ioport_map(unsigned long port, unsigned int nr)
> +{
> +	return (void __iomem *)port;
> +}
> +
> +static inline void ioport_unmap(void __iomem *addr)
> +{
> +}
> +
>  extern void iounmap(const void __iomem *addr);
> +extern int pci_ioremap_io(unsigned int offset, phys_addr_t phys_addr);
>  
>  #define ioremap_nocache(phy, sz)	ioremap(phy, sz)
>  #define ioremap_wc(phy, sz)		ioremap(phy, sz)
> diff --git a/arch/arc/include/asm/mach/pci.h b/arch/arc/include/asm/mach/pci.h
> new file mode 100644
> index 0000000..9e75277
> --- /dev/null
> +++ b/arch/arc/include/asm/mach/pci.h
> @@ -0,0 +1,97 @@
> +/*
> + *  arch/arc/include/asm/mach/pci.h
> + *
> + *  Copyright (C) 2004-2014 Synopsys, Inc. (www.synopsys.com)
> + *
> + * 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.
> + */
> +
> +#ifndef __ASM_MACH_PCI_H
> +#define __ASM_MACH_PCI_H
> +
> +#include <linux/ioport.h>
> +
> +struct pci_sys_data;
> +struct pci_ops;
> +struct pci_bus;
> +struct device;
> +
> +struct hw_pci {
> +#ifdef CONFIG_PCI_DOMAINS
> +	int		domain;
> +#endif
> +	struct pci_ops	*ops;
> +	int		nr_controllers;
> +	void		**private_data;
> +	int		(*setup)(int nr, struct pci_sys_data *);
> +	struct pci_bus *(*scan)(int nr, struct pci_sys_data *);
> +	void		(*preinit)(void);
> +	void		(*postinit)(void);
> +	u8		(*swizzle)(struct pci_dev *dev, u8 *pin);
> +	int		(*map_irq)(const struct pci_dev *dev, u8 slot, u8 pin);
> +	resource_size_t (*align_resource)(struct pci_dev *dev,
> +					  const struct resource *res,
> +					  resource_size_t start,
> +					  resource_size_t size,
> +					  resource_size_t align);
> +	void		(*add_bus)(struct pci_bus *bus);
> +	void		(*remove_bus)(struct pci_bus *bus);
> +};
> +
> +/*
> + * Per-controller structure
> + */
> +struct pci_sys_data {
> +#ifdef CONFIG_PCI_DOMAINS
> +	int		domain;
> +#endif
> +	struct list_head node;
> +	int		busnr;		/* primary bus number		    */
> +	u64		mem_offset;	/* bus->cpu memory mapping offset   */
> +	unsigned long	io_offset;	/* bus->cpu IO mapping offset	    */
> +	struct pci_bus	*bus;		/* PCI bus			    */
> +	struct list_head resources;	/* root bus resources (apertures)   */
> +	struct resource io_res;
> +	char		io_res_name[12];
> +					/* Bridge swizzling		    */
> +	u8		(*swizzle)(struct pci_dev *, u8 *);
> +					/* IRQ mapping			    */
> +	int		(*map_irq)(const struct pci_dev *, u8, u8);
> +					/* Resource alignement requirements */
> +	resource_size_t (*align_resource)(struct pci_dev *dev,
> +					  const struct resource *res,
> +					  resource_size_t start,
> +					  resource_size_t size,
> +					  resource_size_t align);
> +	void		(*add_bus)(struct pci_bus *bus);
> +	void		(*remove_bus)(struct pci_bus *bus);
> +	void		*private_data;	/* platform controller private data */
> +};
> +
> +/*
> + * Call this with your hw_pci struct to initialise the PCI system.
> + */
> +void pci_common_init_dev(struct device *, struct hw_pci *);
> +
> +/*
> + * Compatibility wrapper for older platforms that do not care about
> + * passing the parent device.
> + */
> +static inline void pci_common_init(struct hw_pci *hw)
> +{
> +	pci_common_init_dev(NULL, hw);
> +}

All the above stuff (hw_pci, pci_sys_data, pci_common_init_dev(),
pci_common_init()) appears to be unused.

> +
> +/*
> + * Setup early fixed I/O mapping.
> + */
> +#if defined(CONFIG_PCI)
> +extern void pci_map_io_early(unsigned long pfn);
> +#else
> +static inline void pci_map_io_early(unsigned long pfn) {}
> +#endif
> +
> +#endif /* __ASM_MACH_PCI_H */
> +
> diff --git a/arch/arc/include/asm/pci.h b/arch/arc/include/asm/pci.h
> new file mode 100644
> index 0000000..085b15f
> --- /dev/null
> +++ b/arch/arc/include/asm/pci.h
> @@ -0,0 +1,34 @@
> +/*
> + * Copyright (C) 2015-2016 Synopsys, Inc. (www.synopsys.com)
> + *
> + * 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.
> + */
> +
> +#ifndef _ASM_ARC_PCI_H
> +#define _ASM_ARC_PCI_H
> +
> +#ifdef __KERNEL__
> +#include <asm-generic/pci-dma-compat.h>
> +#include <asm-generic/pci-bridge.h>
> +
> +#include <asm/mach/pci.h> /* for pci_sys_data */
> +
> +extern unsigned long pcibios_min_io;
> +#define PCIBIOS_MIN_IO pcibios_min_io
> +extern unsigned long pcibios_min_mem;
> +#define PCIBIOS_MIN_MEM pcibios_min_mem
> +
> +#define pcibios_assign_all_busses()	1
> +/*
> + * The PCI address space does equal the physical memory address space.
> + * The networking and block device layers use this boolean for bounce
> + * buffer decisions.
> + */
> +#define PCI_DMA_BUS_IS_PHYS     (1)
> +
> +#endif /* __KERNEL__ */
> +
> +#endif /* _ASM_ARC_PCI_H */
> +
> diff --git a/arch/arc/kernel/Makefile b/arch/arc/kernel/Makefile
> index e7f3625..1bc2036 100644
> --- a/arch/arc/kernel/Makefile
> +++ b/arch/arc/kernel/Makefile
> @@ -12,6 +12,7 @@ obj-y	:= arcksyms.o setup.o irq.o time.o reset.o ptrace.o process.o devtree.o
>  obj-y	+= signal.o traps.o sys.o troubleshoot.o stacktrace.o disasm.o clk.o
>  obj-$(CONFIG_ISA_ARCOMPACT)		+= entry-compact.o intc-compact.o
>  obj-$(CONFIG_ISA_ARCV2)			+= entry-arcv2.o intc-arcv2.o
> +obj-$(CONFIG_PCI)  			+= pcibios.o
>  
>  obj-$(CONFIG_MODULES)			+= arcksyms.o module.o
>  obj-$(CONFIG_SMP) 			+= smp.o
> diff --git a/arch/arc/kernel/pcibios.c b/arch/arc/kernel/pcibios.c
> new file mode 100644
> index 0000000..5af7bf0
> --- /dev/null
> +++ b/arch/arc/kernel/pcibios.c
> @@ -0,0 +1,358 @@
> +/*
> + * Copyright (C) 2014-2015 Synopsys, Inc. (www.synopsys.com)
> + *
> + * 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.
> + *
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/pci.h>
> +#include <linux/delay.h>
> +#include <linux/string.h>
> +#include <linux/init.h>
> +#include <linux/sched.h>
> +#include <linux/errno.h>
> +#include <linux/bootmem.h>
> +#include <linux/sizes.h>
> +#include <linux/slab.h>
> +
> +#include <asm/pci.h>
> +#include <asm/mach/pci.h>
> +
> +unsigned long pcibios_min_io = 0x100;
> +EXPORT_SYMBOL(pcibios_min_io);
> +
> +unsigned long pcibios_min_mem = 0x100000;
> +EXPORT_SYMBOL(pcibios_min_mem);
> +
> +static int pcibios_init_resources(int busnr, struct pci_sys_data *sys)
> +{
> +	int ret;
> +	struct resource_entry *window;
> +
> +	if (list_empty(&sys->resources)) {
> +		pci_add_resource_offset(&sys->resources,
> +			 &iomem_resource, sys->mem_offset);
> +	}
> +
> +	resource_list_for_each_entry(window, &sys->resources) {
> +		if (resource_type(window->res) == IORESOURCE_IO)
> +			return 0;
> +	}
> +
> +	sys->io_res.start = (busnr * SZ_64K) ?  : pcibios_min_io;
> +	sys->io_res.end = (busnr + 1) * SZ_64K - 1;
> +	sys->io_res.flags = IORESOURCE_IO;
> +	sys->io_res.name = sys->io_res_name;
> +	sprintf(sys->io_res_name, "PCI%d I/O", busnr);
> +
> +	ret = request_resource(&ioport_resource, &sys->io_res);
> +	if (ret) {
> +		pr_err("PCI: unable to allocate I/O port region (%d)\n", ret);
> +		return ret;
> +	}
> +	pci_add_resource_offset(&sys->resources, &sys->io_res,
> +				sys->io_offset);
> +
> +	return 0;
> +}

Appears unused.

> +static void pcibios_init_hw(struct device *parent, struct hw_pci *hw,
> +			    struct list_head *head)
> +{
> +	struct pci_sys_data *sys = NULL;
> +	int ret;
> +	int nr, busnr;
> +
> +	for (nr = busnr = 0; nr < hw->nr_controllers; nr++) {
> +		sys = kzalloc(sizeof(struct pci_sys_data), GFP_KERNEL);
> +		if (!sys)
> +			panic("PCI: unable to allocate sys data!");
> +
> +#ifdef CONFIG_PCI_DOMAINS
> +		sys->domain  = hw->domain;
> +#endif
> +		sys->busnr   = busnr;
> +		sys->swizzle = hw->swizzle;
> +		sys->map_irq = hw->map_irq;
> +		sys->align_resource = hw->align_resource;
> +		sys->add_bus = hw->add_bus;
> +		sys->remove_bus = hw->remove_bus;
> +		INIT_LIST_HEAD(&sys->resources);
> +
> +
> +		if (hw->private_data)
> +			sys->private_data = hw->private_data[nr];
> +
> +		ret = hw->setup(nr, sys);
> +
> +		if (ret > 0) {
> +			ret = pcibios_init_resources(nr, sys);
> +			if (ret)  {
> +				kfree(sys);
> +				break;
> +			}
> +
> +			if (hw->scan)
> +				sys->bus = hw->scan(nr, sys);
> +			else
> +				sys->bus = pci_scan_root_bus(parent, sys->busnr,
> +						hw->ops, sys, &sys->resources);
> +
> +			if (!sys->bus)
> +				panic("PCI: unable to scan bus!");
> +
> +			busnr = sys->bus->busn_res.end + 1;
> +
> +			list_add(&sys->node, head);
> +		} else {
> +			kfree(sys);
> +			if (ret < 0)
> +				break;
> +		}
> +	}
> +}

Appears unused.

> +int pcibios_root_bridge_prepare(struct pci_host_bridge *bridge)
> +{
> +	return 0;
> +}
> +
> +void pcibios_add_bus(struct pci_bus *bus)
> +{
> +}
> +
> +void pcibios_remove_bus(struct pci_bus *bus)
> +{
> +}

The above three are Unnecessary since drivers/pci/probe.c defines
default (weak) versions.

> +/*
> + * Swizzle the device pin each time we cross a bridge.  If a platform does
> + * not provide a swizzle function, we perform the standard PCI swizzling.
> + *
> + * The default swizzling walks up the bus tree one level at a time, applying
> + * the standard swizzle function at each step, stopping when it finds the PCI
> + * root bus.  This will return the slot number of the bridge device on the
> + * root bus and the interrupt pin on that device which should correspond
> + * with the downstream device interrupt.
> + *
> + * Platforms may override this, in which case the slot and pin returned
> + * depend entirely on the platform code.  However, please note that the
> + * PCI standard swizzle is implemented on plug-in cards and Cardbus based
> + * PCI extenders, so it can not be ignored.
> + */
> +static u8 pcibios_swizzle(struct pci_dev *dev, u8 *pin)
> +{
> +	int slot;
> +	struct pci_sys_data *sys = dev->sysdata;
> +
> +	if (sys->swizzle)
> +		slot = sys->swizzle(dev, pin);
> +	else
> +		slot = pci_common_swizzle(dev, pin);
> +
> +	return slot;
> +}

Appears unused.

> +/*
> + * Map a slot/pin to an IRQ.
> + */
> +static int pcibios_map_irq(const struct pci_dev *dev, u8 slot, u8 pin)
> +{
> +	struct pci_sys_data *sys = dev->sysdata;
> +	int irq = -1;
> +
> +	if (sys->map_irq)
> +		irq = sys->map_irq(dev, slot, pin);
> +
> +	return irq;
> +}

Appears unused.

> +void pci_common_init_dev(struct device *parent, struct hw_pci *hw)
> +{
> +	struct pci_sys_data *sys;
> +	LIST_HEAD(head);
> +
> +	pci_add_flags(PCI_REASSIGN_ALL_RSRC);
> +	if (hw->preinit)
> +		hw->preinit();
> +	pcibios_init_hw(parent, hw, &head);
> +	if (hw->postinit)
> +		hw->postinit();
> +
> +	pci_fixup_irqs(pcibios_swizzle, pcibios_map_irq);
> +
> +	list_for_each_entry(sys, &head, node) {
> +		struct pci_bus *bus = sys->bus;
> +
> +		if (!pci_has_flag(PCI_PROBE_ONLY)) {
> +			/*
> +			 * Size the bridge windows.
> +			 */
> +			pci_bus_size_bridges(bus);
> +
> +			/*
> +			 * Assign resources.
> +			 */
> +			pci_bus_assign_resources(bus);
> +		}
> +
> +		/*
> +		 * Tell drivers about devices found.
> +		 */
> +		pci_bus_add_devices(bus);
> +	}
> +}

Appears unused.

> +/*
> + * We don't have to worry about legacy ISA devices, so nothing to do here
> + */
> +resource_size_t pcibios_align_resource(void *data, const struct resource *res,
> +				resource_size_t size, resource_size_t align)
> +{
> +	return res->start;
> +}
> +
> +/**
> + * pcibios_enable_device - Enable I/O and memory.
> + * @dev: PCI device to be enabled
> + */
> +int pcibios_enable_device(struct pci_dev *pci_dev, int mask)
> +{
> +	u16 cmd, old_cmd;
> +	int idx;
> +	struct resource *r;
> +
> +	pci_read_config_word(pci_dev, PCI_COMMAND, &cmd);
> +	old_cmd = cmd;
> +	for (idx = 0; idx < 6; idx++) {
> +		/* Only set up the requested stuff */
> +		if (!(mask & (1 << idx)))
> +			continue;
> +
> +		r = pci_dev->resource + idx;
> +		if (!r->start && r->end) {
> +			dev_err(&pci_dev->dev, "PCI: Device %s not available\n",
> +							pci_name(pci_dev));
> +			return -EINVAL;
> +		}
> +		if (r->flags & IORESOURCE_IO)
> +			cmd |= PCI_COMMAND_IO;
> +		if (r->flags & IORESOURCE_MEM)
> +			cmd |= PCI_COMMAND_MEMORY;
> +	}
> +
> +	/*
> +	 * Bridges (eg, cardbus bridges) need to be fully enabled
> +	 */
> +	if ((pci_dev->class >> 16) == PCI_BASE_CLASS_BRIDGE)
> +		cmd |= PCI_COMMAND_IO | PCI_COMMAND_MEMORY;
> +
> +	if (cmd != old_cmd) {
> +		pr_info("PCI: enabling device %s (%04x -> %04x)\n",
> +		       pci_name(pci_dev), old_cmd, cmd);
> +		pci_write_config_word(pci_dev, PCI_COMMAND, cmd);
> +	}
> +	return 0;
> +}

There's a default (weak) version of pcibios_enable_device().  You
should omit this definition and use the default unless your arch
requires something special.

> +
> +/*
> + * If the bus contains any of these devices, then we must not turn on
> + * parity checking of any kind.  Currently this is CyberPro 20x0 only.
> + */
> +static inline int pdev_bad_for_parity(struct pci_dev *dev)
> +{
> +	return ((dev->vendor == PCI_VENDOR_ID_INTERG &&
> +		 (dev->device == PCI_DEVICE_ID_INTERG_2000 ||
> +		  dev->device == PCI_DEVICE_ID_INTERG_2010)) ||
> +		(dev->vendor == PCI_VENDOR_ID_ITE &&
> +		 dev->device == PCI_DEVICE_ID_ITE_8152));
> +
> +}
> +
> +/*
> + * pcibios_fixup_bus - Called after each bus is probed,
> + * but before its children are examined.
> + */
> +void pcibios_fixup_bus(struct pci_bus *bus)
> +{
> +	struct pci_dev *dev;
> +	u16 features = PCI_COMMAND_SERR | PCI_COMMAND_PARITY
> +			| PCI_COMMAND_FAST_BACK;
> +
> +	/*
> +	 * Walk the devices on this bus, working out what we can
> +	 * and can't support.
> +	 */
> +	list_for_each_entry(dev, &bus->devices, bus_list) {
> +		u16 status;
> +
> +		pci_read_config_word(dev, PCI_STATUS, &status);
> +
> +		/*
> +		 * If any device on this bus does not support fast back
> +		 * to back transfers, then the bus as a whole is not able
> +		 * to support them.  Having fast back to back transfers
> +		 * on saves us one PCI cycle per transaction.
> +		 */
> +		if (!(status & PCI_STATUS_FAST_BACK))
> +			features &= ~PCI_COMMAND_FAST_BACK;
> +
> +		if (pdev_bad_for_parity(dev))
> +			features &= ~(PCI_COMMAND_SERR | PCI_COMMAND_PARITY);
> +
> +		switch (dev->class >> 8) {
> +		case PCI_CLASS_BRIDGE_PCI:
> +			pci_read_config_word(dev, PCI_BRIDGE_CONTROL, &status);
> +			status |= PCI_BRIDGE_CTL_PARITY
> +					|PCI_BRIDGE_CTL_MASTER_ABORT;
> +			status &= ~(PCI_BRIDGE_CTL_BUS_RESET
> +					|PCI_BRIDGE_CTL_FAST_BACK);
> +			pci_write_config_word(dev, PCI_BRIDGE_CONTROL, status);
> +			break;
> +
> +		case PCI_CLASS_BRIDGE_CARDBUS:
> +			pci_read_config_word(dev, PCI_CB_BRIDGE_CONTROL,
> +						&status);
> +			status |= PCI_CB_BRIDGE_CTL_PARITY
> +					|PCI_CB_BRIDGE_CTL_MASTER_ABORT;
> +			pci_write_config_word(dev, PCI_CB_BRIDGE_CONTROL,
> +						status);
> +			break;
> +		}
> +	}
> +
> +	/*
> +	 * Now walk the devices again, this time setting them up.
> +	 */
> +	list_for_each_entry(dev, &bus->devices, bus_list) {
> +		u16 cmd;
> +
> +		pci_read_config_word(dev, PCI_COMMAND, &cmd);
> +		cmd |= features;
> +		pci_write_config_word(dev, PCI_COMMAND, cmd);
> +
> +		pci_write_config_byte(dev, PCI_CACHE_LINE_SIZE,
> +				      L1_CACHE_BYTES >> 2);
> +	}
> +
> +	/*
> +	 * Propagate the flags to the PCI bridge.
> +	 */
> +	if (bus->self && bus->self->hdr_type == PCI_HEADER_TYPE_BRIDGE) {
> +		if (features & PCI_COMMAND_FAST_BACK)
> +			bus->bridge_ctl |= PCI_BRIDGE_CTL_FAST_BACK;
> +		if (features & PCI_COMMAND_PARITY)
> +			bus->bridge_ctl |= PCI_BRIDGE_CTL_PARITY;
> +	}
> +
> +	/*
> +	 * Report what we did for this bus
> +	 */
> +	pr_info("PCI: bus%d: Fast back to back transfers %sabled\n",
> +		bus->number, (features & PCI_COMMAND_FAST_BACK) ? "en" : "dis");
> +}
> +EXPORT_SYMBOL(pcibios_fixup_bus);

This pcibios_fixup_bus() implementation has been blindly copied all
over the place, but I don't think it's relevant for most arches.  I
think you could probably make it an empty function as on arm64.

> diff --git a/arch/arc/mm/ioremap.c b/arch/arc/mm/ioremap.c
> index 739e65f..fe807b0 100644
> --- a/arch/arc/mm/ioremap.c
> +++ b/arch/arc/mm/ioremap.c
> @@ -13,6 +13,7 @@
>  #include <linux/mm.h>
>  #include <linux/slab.h>
>  #include <linux/cache.h>
> +#include <linux/sizes.h>
>  
>  void __iomem *ioremap(unsigned long paddr, unsigned long size)
>  {
> @@ -80,7 +81,6 @@ void __iomem *ioremap_prot(phys_addr_t paddr, unsigned long size,
>  }
>  EXPORT_SYMBOL(ioremap_prot);
>  
> -
>  void iounmap(const void __iomem *addr)
>  {
>  	if (addr >= (void __force __iomem *)ARC_UNCACHED_ADDR_SPACE)
> @@ -89,3 +89,11 @@ void iounmap(const void __iomem *addr)
>  	vfree((void *)(PAGE_MASK & (unsigned long __force)addr));
>  }
>  EXPORT_SYMBOL(iounmap);
> +
> +#ifdef CONFIG_PCI
> +int pci_ioremap_io(unsigned int offset, phys_addr_t phys_addr)
> +{
> +	return ioremap_nocache(phys_addr + offset,  SZ_64K);
> +}
> +EXPORT_SYMBOL_GPL(pci_ioremap_io);
> +#endif
> diff --git a/arch/arc/plat-axs10x/Kconfig b/arch/arc/plat-axs10x/Kconfig
> index d475f9d..426ac4b 100644
> --- a/arch/arc/plat-axs10x/Kconfig
> +++ b/arch/arc/plat-axs10x/Kconfig
> @@ -11,6 +11,7 @@ menuconfig ARC_PLAT_AXS10X
>  	select DW_APB_ICTL
>  	select GPIO_DWAPB
>  	select OF_GPIO
> +	select MIGHT_HAVE_PCI
>  	select GENERIC_IRQ_CHIP
>  	select ARCH_REQUIRE_GPIOLIB
>  	help
> diff --git a/drivers/pci/Makefile b/drivers/pci/Makefile
> index be3f631..2154092 100644
> --- a/drivers/pci/Makefile
> +++ b/drivers/pci/Makefile
> @@ -32,6 +32,7 @@ obj-$(CONFIG_PCI_IOV) += iov.o
>  # Some architectures use the generic PCI setup functions
>  #
>  obj-$(CONFIG_ALPHA) += setup-irq.o
> +obj-$(CONFIG_ARC) += setup-irq.o
>  obj-$(CONFIG_ARM) += setup-irq.o
>  obj-$(CONFIG_ARM64) += setup-irq.o
>  obj-$(CONFIG_UNICORE32) += setup-irq.o
> -- 
> 1.8.1.5
> 
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