[PATCH 03/15] ARM: tegra: use fixed PCI i/o mapping

[robherring2@gmail.com (Rob Herring)]

On 07/08/2012 11:35 AM, Arnd Bergmann wrote:
> On Sunday 08 July 2012, Rob Herring wrote:
>>> I'm not very familiar with the inner workings of the iotable and the
>>> mappings initialized by it, but I wonder if this can be done dynamically
>>> at a later stage. The way this is currently done in this patch, the I/O
>>> region is statically mapped from a fixed offset within the PCIe address
>>> range. Part of the patches to add DT support is to allow this region to
>>> be defined by the DT, so that will obviously also create problems.
>>
>> Is the i/o address something you could extract from DT earlier? This can
>> be done separately if it doesn't require information from the driver.
>>
>> I'm sure exactly how to do a fixed virtual mapping other than the
>> io_table mappings. There was some discussion of use fixmap region
>> previously, but doing so will be a bit more complex. I'll look into this
>> some.
> 
> I think you can call ioremap_page_range() to do this.

Thanks for the pointer. But this has to be in 2 steps. First reserve the
virtual space and then map it. For the first part I think something like
this function will work:

void __init pci_reserve_io(void)
{
	struct vm_struct *vm;

	vm = early_alloc_aligned(sizeof(*vm), __alignof__(*vm));

	vm->addr = (void *)PCI_IO_VIRT_BASE;
	vm->size = SZ_1M;
	vm->phys_addr = 0;
	vm->flags = VM_IOREMAP | VM_ARM_STATIC_MAPPING;
	vm->flags |= VM_ARM_MTYPE(MT_DEVICE);
	vm->caller = pci_reserve_io;
	vm_area_add_early(vm++);
}

There's a big fat warning on vm_area_add_early from Nico to not use
unless you know what you're doing. I'll pretend I do...

Rob