Re: [PATCH v2 05/27] arm: pci: add a align_resource hook

[Arnd Bergmann <arnd@arndb.de>]

On Wednesday 30 January 2013, Thomas Petazzoni wrote:

> I am not sure where this 0xfee00000 address comes from, but in my case
> (and I think in the Tegra PCI driver as well), we tell the Linux PCI
> core from which addresses the I/O ranges should be allocated. In my DT,
> I have:
> 
>                         ranges = <0x00000800 0 0xd0040000 0xd0040000 0 0x00002000   /* port 0.0 registers */
>                                   0x00004800 0 0xd0042000 0xd0042000 0 0x00002000   /* port 2.0 registers */
>                                   0x00001000 0 0xd0044000 0xd0044000 0 0x00002000   /* port 0.1 registers */
>                                   0x00001800 0 0xd0048000 0xd0048000 0 0x00002000   /* port 0.2 registers */
>                                   0x00002000 0 0xd004C000 0xd004C000 0 0x00002000   /* port 0.3 registers */
>                                   0x00002800 0 0xd0080000 0xd0080000 0 0x00002000   /* port 1.0 registers */
>                                   0x00005000 0 0xd0082000 0xd0082000 0 0x00002000   /* port 3.0 registers */
>                                   0x00003000 0 0xd0084000 0xd0084000 0 0x00002000   /* port 1.1 registers */
>                                   0x00003800 0 0xd0088000 0xd0088000 0 0x00002000   /* port 1.2 registers */
>                                   0x00004000 0 0xd008C000 0xd008C000 0 0x00002000   /* port 1.3 registers */
>                                   0x81000000 0 0          0xc0000000 0 0x00100000   /* downstream I/O */
>                                   0x82000000 0 0          0xc1000000 0 0x08000000>; /* non-prefetchable memory */
> 
> And then, the Marvell PCI driver gets the "downstream I/O" range,
> parses it into a "struct resource", and then does (where &pcie->io is
> the struct resource into which we parsed the "downstream I/O" range):
> 
>         pci_add_resource_offset(&sys->resources, &pcie->io, sys->io_offset);
> 	[...]
> 	pci_ioremap_io(nr * SZ_64K, pcie->io.start);

0xfee00000 is the platform independent virtual address that pci_ioremap_io
maps your platform specific physical address (from pcie->io.start) to. It's
defined (in the kernel I am looking at) in asm/io.h as

#define PCI_IO_VIRT_BASE        0xfee00000

and used by pci_ioremap_io as

        return ioremap_page_range(PCI_IO_VIRT_BASE + offset,
                                  PCI_IO_VIRT_BASE + offset + SZ_64K,
                                  phys_addr,
                                  __pgprot(get_mem_type(MT_DEVICE)->prot_pte));


> And it works just fine, I get my I/O ranges allocated at 0xc0000000 for
> the first device, 0xc0010000 (i.e base address + 64KB) for the second
> device, etc.

(void*)0xc0000000 is the normal PAGE_OFFSET. If you map your I/O space there,
you are in big trouble because that is supposed to have the start of your
physical memory mapping.

	Arnd