Re: RFC: [PATCH 1/3] Enhance platform support for PCI

[Ian Campbell <ian.campbell@citrix.com>]

On Thu, 2015-02-26 at 15:39 +0530, Manish Jaggi wrote:
> Have you reached a conclusion?

My current thinking on how PCI for Xen on ARM should look is thus:

xen/arch/arm/pci.c:

        New file, containing core PCI infrastructure for ARM. Includes:
        
        pci_hostbridge_register(), which registers a host bridge:
        
                Registration includes:
                        DT node pointer
                        
                        CFG space address
                
                        pci_hostbridge_ops function table, which
                        contains e.g. cfg space read/write ops, perhaps
                        other stuff).
        
        Function for setting the (segment,bus) for a given host bridge.
        Lets say pci_hostbridge_setup(), the host bridge must have been
        previously registered. Looks up the host bridge via CFG space
        address and maps that to (segment,bus).
        
        Functions for looking up host bridges by various keys as needed
        (cfg base address, DT node, etc)
        
        pci_init() function, called from somewhere appropriate in
        setup.c which calls device_init(node, DEVICE_PCIHOST, NULL) (see
        gic_init() for the shape of this)
        
        Any other common helper functions for managing PCI devices, e.g.
        for implementing PHYSDEVOP_*, which cannot be made properly
        common (i.e. shared with x86).

xen/drivers/pci/host-*.c (or pci/host/*.c):

        New files, one per supported PCI controller IP block. Each
        should use the normal DT_DEVICE infrastructure for probing,
        i.e.:
        DT_DEVICE_START(foo, "FOO", DEVICE_PCIHOST)
        
        Probe function should call pci_hostbridge_register() for each
        host bridge which the controller exposes.
        
xen/arch/arm/physdev.c:

        Implements do_physdev_op handling PHYSDEVOP_*. Includes:
        
        New hypercall subop PHYSDEVOP_pci_host_bridge_add:
        
                As per 1424703761.27930.140.camel@citrix.com> which
                calls pci_hostbridge_setup() to map the (segment,bus) to
                a specific pci_hostbridge_ops (i.e. must have previously
                been registered with pci_hostbridge_register(), else
                error).
        
        PHYSDEVOP_pci_device_add/remove: Implement existing hypercall
        interface used by x86 for ARM.
        
                This requires that PHYSDEVOP_pci_host_bridge_add has
                been called for the (segment,bus) which it refers to,
                otherwise error.
                
                Looks up the host bridge and does whatever setup is
                required plus e.g. calling of pci_add_device().

No doubt various other existing interfaces will need wiring up, e.g.
pci_conf_{read,write}* should lookup the host bridge ops struct and call
the associated method.

I'm sure the above must be incomplete, but I hope the general shape
makes sense?

Ian.