mapping small parts of a pci card to conserve KVA

[Scott Long]

Andrew Gallatin wrote:

> I maintain drivers for a PCI card which presents itself as having
> 16MB of address space.  Eg:
> 
> mx0: <Myrinet PCIXE> mem 0xf9000000-0xf9ffffff irq 20 at device 3.0 on pci1
> 
> However, most of that address space does not need to be mapped into
> the host.  Really, only a little over 2MB needs to be mapped (3 regions
> with length 1024 bytes, 256 bytes, and 2MB).
> 
> I've tried to re-write things so that I make multiple calls
> to bus_alloc_resource() with the (hopefully) appropriate offset and
> lengths.  Eg:
> 
>   rid = PCIR_MAPS;
>   *res = bus_alloc_resource(is->arch.dev, SYS_RES_MEMORY, &rid,
> 	     (u_long)offset, 
>  	     (u_long)(offset + len - 1), len, 
>              RF_ACTIVE|PCI_RF_DENSE);
> 
> At least on 5.3R, I seem to get back the same struct resource * from
> each call.  rman_get_virtual() returns a different kva for each
> mapping, yet they all seem to map to the same physical address. 
> Eg, I call vtophys() on the results of rman_get_virtual(),
> for each segment, and they all map to 0xf9000000.
> 
> Is there a way to just map what I need?
> 
> Thanks,
> 
> Drew
> 

You can use pmap_mapdev() to create a KVA mapping of an arbitrary
physaddr+len.  In fact, this is exactly what newbus uses to create the
PCI MEMIO resources when bus_alloc_resource() is called.  I'm not sure
if the range is mapped and activated before the driver makes that call,
Warner or John might know for sure.

Scott