Doubt regarding PCI access in ixp425 arch

[srikanth <sri@xxxxxxxxxxxxxxxxxx>]

Hi all..

		I am working on a ixp425 up. I see that the __arch_ioremap function
(in asm/arch/) is having a check for the pci region as below, which
dis-allows io-remapping of the pci region.

static inline void *
__arch_ioremap(unsigned long phys_addr, size_t size, unsigned long
flags)
{
	extern void * __ioremap(unsigned long, size_t, unsigned long);

	if((phys_addr < 0x48000000) || (phys_addr > 0x4bffffff))
		return __ioremap(phys_addr, size, flags);

	return (void *)phys_addr;
}

Further, by the comments in the file i understood that the ixp425 has to
access the pci region in a different way, but could not figure it out
what does that mean exactly.

 /*
 * IXP425 does not have a transparent cpu -> PCI I/O translation
 * window.  Instead, it has a set of registers that must be tweaked
 * with the proper byte lanes, command types, and address for the
 * transaction.  This means that we need to override the default
 * I/O functions.
 */

/*
 * IXP425 also does not have a transparent PCI MEM translation
 * window.  For this reason, we have to use the NP registers for
 * all PCI mem acceses and have to implement custom 
 * ioremap/unmap/etc functions. :( We need to check and make
 * sure that the address being accessed is a PCI address and
 * if not, fall back to the normal code.
 */


Can anyone please explain what does this mean..

Thanks in advance..


Srikanth



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