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[IA64] ia64: add ar.k0 usage note

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Update comment about how ar.k0 is used.  Make the initialization the
same as in start_secondary() (no functional change, just make it look
more similar).

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
This commit is contained in:
Bjorn Helgaas 2005-09-16 11:43:10 -06:00 committed by Tony Luck
parent 044a500e46
commit 44c451208d
1 changed files with 16 additions and 13 deletions
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29
arch/ia64/kernel/setup.c
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@ -244,28 +244,31 @@ find_initrd (void)
static void __init
io_port_init (void)
{
extern unsigned long ia64_iobase;
unsigned long phys_iobase;
/*
* Set `iobase' to the appropriate address in region 6 (uncached access range).
* Set `iobase' based on the EFI memory map or, failing that, the
* value firmware left in ar.k0.
*
* The EFI memory map is the "preferred" location to get the I/O port space base,
* rather the relying on AR.KR0. This should become more clear in future SAL
* specs. We'll fall back to getting it out of AR.KR0 if no appropriate entry is
* found in the memory map.
* Note that in ia32 mode, IN/OUT instructions use ar.k0 to compute
* the port's virtual address, so ia32_load_state() loads it with a
* user virtual address. But in ia64 mode, glibc uses the
* *physical* address in ar.k0 to mmap the appropriate area from
* /dev/mem, and the inX()/outX() interfaces use MMIO. In both
* cases, user-mode can only use the legacy 0-64K I/O port space.
*
* ar.k0 is not involved in kernel I/O port accesses, which can use
* any of the I/O port spaces and are done via MMIO using the
* virtual mmio_base from the appropriate io_space[].
*/
phys_iobase = efi_get_iobase();
if (phys_iobase)
/* set AR.KR0 since this is all we use it for anyway */
ia64_set_kr(IA64_KR_IO_BASE, phys_iobase);
else {
if (!phys_iobase) {
phys_iobase = ia64_get_kr(IA64_KR_IO_BASE);
printk(KERN_INFO "No I/O port range found in EFI memory map, falling back "
"to AR.KR0\n");
printk(KERN_INFO "I/O port base = 0x%lx\n", phys_iobase);
printk(KERN_INFO "No I/O port range found in EFI memory map, "
"falling back to AR.KR0 (0x%lx)\n", phys_iobase);
}
ia64_iobase = (unsigned long) ioremap(phys_iobase, 0);
ia64_set_kr(IA64_KR_IO_BASE, __pa(ia64_iobase));
/* setup legacy IO port space */
io_space[0].mmio_base = ia64_iobase;