On Mon, Jan 30, 2006 at 02:49:26PM -0800, Garrett D'Amore wrote:

> Good.  What I will do is go ahead and commit *that* change seperately,
> and then commit the PCI code which depends on it after I have changed
> it. :-)
>
> Any objections (Simon?)  Speak up now, please!

My first broad comment on the PCI-specific parts was the name of the
device (aupb) - I would have preferred aupci, or at a stretch aupcib
to keep in line with the current naming conventions.  There was a stub
entry already in the aubus attachment code for aupci.

I'm still not conviced about wiring down gobs of memory for PCI vs
normal allocation and faulting in the pages to the TLB when needed, but
I'm still open to being convinced this is a win for large areas of PCI
memory space like frame buffers.

Just to check my memory, we wire down a TLB per 32MB of wired space we
reserve?  So your PCI patch will wire down 288MB (256MB of PCI mem, 16MB
of PCI IO and 16MB of PCI config) or 9 TLB entries regardless of how
much space is needed?  This is close to a third of our total TLB count
and I'm worried about the performance hit that might cause.  Perhaps
we could do the wiring after calling pci_configure_bus() (or otherwise
in the non-PCI_NETBSD_CONFIGURE case) when we know how much space we
actually need, and then wire only what we do need.

PCI config space access pretty much only occur during system startup,
and otherwise if you run "pcictl dump" or similar.  It seems a waste to
burn a wired TLB entry for the life of the system for this use.  I think
we can get away with just using uvm_km_alloc/pmap_kenter_pa when needed,
or perhaps just reserve a single 4kB page with uvm_km_alloc once and
enter a different PA each time we need to do a config cycle.

I'm really trying to get away from using as many wired TLB entries as we
can - the more often we need to recycle non-wired TLB entries the more
performance in general is going to get hurt.


With the existing wired entries you have now, I wonder if something like:

#define        AU_PCI_MEM_VA           0xf0000000
#define        AU_PCI_MEM_SZ           0x0e000000    /* 224 MB */

#define        AU_PCI_IO_VA            0xfe000000
#define        AU_PCI_IO_SZ            0x01000000    /* 16 MB */

#define        AU_PCI_CFG_VA           0xff000000
#define        AU_PCI_CFG_SZ           0x01000000    /* 16 MB, overkill */

would work better, with all the entries being contiguous?  This
gives KSEG2 more room for growth if the kernel needs VA for other
purposes.  Or if we don't need to wire down an entry for PCI config,
then 240MB/16MB for PCI mem/IO.

Simon.
--
Simon Burge                                   <simonb@wasabisystems.com>
NetBSD Development, Support and Service:   http://www.wasabisystems.com/