mapping small parts of a pci card to conserve KVA

[Warner Losh]

From: Scott Long <scottl at samsco.org>
Subject: Re: mapping small parts of a pci card to conserve KVA
Date: Tue, 15 Feb 2005 14:03:12 -0700

> 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.

If you go that route, you need to allocate the resource (all of it).
RF_ACTIVE in the flags, or bus_activate_resource is what maps it in,
so if you don't do that, you can call pmap_mamdev.

Warner