Re: Doubt regarding PCI access in ixp425 arch

[srikanth <sri@xxxxxxxxxxxxxxxxxx>]

Hi.. 
	Just to add a note..

	The kernel version i am referring to is 2.4.20.

On Thu, 2006-01-05 at 16:48, srikanth wrote:
> 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 same 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.
> 
> These are the comments in the file
>  /*
>  * 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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-- 
Regards,

Srikanth.P

Development Engineer,
Banyan Networks,
(Broadband Division of
Midas Communications Pvt. Ltd.)
Chennai -India
GSM: +91-988-433-9-789


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