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SubjectRe: Physical memory addresses/PCI memory addresses/io_remap
On 14 Dec 00 at 15:16, Russell King wrote:
> virtual space - address space that the kernel runs in
> physical space - address space that the CPU sits in
> PCI memory space - memory address space that the PCI peripherals sit in
== bus address...
>
> Many, if not all ARM architectures have physical address 0 different from
> PCI memory address 0.
>
> According to include/linux/fb.h, fb drivers should place a physical address
> into "fix.smem_start" and "fix.mmio_start", which can then be passed to
> io_remap_page_range.
>
> 1. Should pci_resource_start be returning the PCI memory space address or
> a physical memory space address?

I believe that pci_resource_start() should return physical address, not
bus one. It already happens on PReP.

> 3. Do we need a macro to convert PCI memory space addresses to physical
> memory space addresses?

No. You need PCI memory space address only for busmastering transfers.
And for PCI DMA there is specialized API... Currently all bus -> physical
mapping should be hidden in platform specific PCI code.

> 4. What does this mean for ioremap? (currently, on ARM, ioremap takes
> PCI memory space addresses, not a physical memory address, which makes
> the physmap MTD driver technically broken).

And ioremap() should take physical address, returning virtual one.
Best regards,
Petr Vandrovec
vandrove@vc.cvut.cz

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