Re: PCI Express support for 2.4 kernel

[Vladimir Kondratiev]

Got it.
Should I understand it this way: for system with >=1Gb RAM, I will be 
unable to ioremap 256Mb region?
It looks confusing. On my test system (don't ask details, I am not 
alowed to share this info), I see
video controller with 256Mb BAR. Does it mean this controller will not 
work as well?

There is alternative solution, for each transaction to ioremap/unmap 
corresponded page.
I don't like it, it involves huge overhead.

I thought about remapping only pages that have actual PCI devices behind,
but this is problematic: access to config goes not always through 
pci_exp_read_config_xxx and alike, raw access with bus/dev/fn numbers 
used as well. And in 2.6, correct me if I wrong, raw access using 
bus/dev/fn numbers goes to be the only way. Per-device access replaced 
with per-bus, at least.

I can statically remap only region for existing buses, this will be huge 
save. It is 1MB per bus, this lead to typical 2-3MB instead of 256. To 
be sure I can do this, I need to know that new bus can't be added on run 
time. I don't think it is true, isn't it? Or do we have single point to 
capture hot plug for new bus?

Vladimir.

Arjan van de Ven wrote:

> > I should be missing something here. You have 256M of physical address 
> > space at 0xe0000000 occupied.
> > You can do nothing with it, it is simply present. Then, ioremap maps it 
> > somewhere in high memory.
> > It should not conflict with kernel RAM, for which trivial mapping (+3G) 
> > used.
> >    
>
> the thing is that typically you have a maximum of 168Mb or so of
> ioremap/vmalloc space (they share the same pool). That is, ff your
> system has >= 1Gb of ram, if it has less ran the ioremap/vmalloc space
> is bigger....
>
>  

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