Date: Tue, 17 Jun 2003 22:49:40 -0400 (EDT) From: Andrew Gallatin <gallatin@cs.duke.edu> To: ticso@cicely.de Cc: freebsd-alpha@freebsd.org Subject: Re: 5.1beta2 on Alpha ES40 w/ 32GB pys ram Message-ID: <16111.54084.284151.643826@grasshopper.cs.duke.edu> In-Reply-To: <20030618005958.GD3626@cicely12.cicely.de> References: <16094.16676.273466.121560@grasshopper.cs.duke.edu> <20030613190624.W36168-100000@mail.chesapeake.net> <16110.27799.68056.48679@grasshopper.cs.duke.edu> <20030618005958.GD3626@cicely12.cicely.de>
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Bernd Walter writes: > On Mon, Jun 16, 2003 at 09:19:19PM -0400, Andrew Gallatin wrote: > > > > Jeff Roberson writes: > > > On Wed, 4 Jun 2003, Andrew Gallatin wrote: > > > > > > > > > > > > > > > Andrea Cocito writes: > > > > > Hallo, > > > > > > > > > > I have a little (??) problem trying to boot FreeBSD 5.1beta2 > > > > > on an ES40 with 32 gigs of physical RAM, this is the status: > > > > > > > > > > > > > You have to limit physical memory to 2GB or less. Otherwise, DMAs > > > > won't work. > > > > > > > > Drew > > > > > > Is this because we dont program the TLB on the DMA controller? I heard > > > rumors that sparc64 has code to handle all of this for their chipsets. If > > > they have the infrastructure it may not be hard to port. > > > > > > > We program it, but we do not take full advantage of it: > > > > Most alphas have 4 DMA windows. We typically use 1 window for ISA > > Do you have an overview of which ones don't have 4 windows? > Is the direct map sufficient for them or can we increase the ISA map > size in such a case? Its been so long that I do not remember. I know for certain that the API UP1x00 boxes don't but they use an AMD chipset. All the important ones do, that I know of. (mcpcia, tsunami, marvel) > > dma, meaning we can do zero-copy (no bounce buffer) DMA to any ISA > > device. This is only 16MB in size. > > > > We use another window as a 'direct map' window, meaning we map > > physical addresses 0..1GB (or 0..2GB) into PCI address space, > > generally at offset 1GB in PCI address space. > > What are the reasons for this difference? > Is it just because of SRM interaction or some chipset limitation? Its because of where the SRM puts the memory space. Ie, on some machiens, SRM puts the memory space on PCI adaptors at 2GB. so if we put a window at 2GB, then there would be 2 devices with address 2GB on the same bus. If we did what I've heard linux does, and took care of reallocating the memory regions on the PCI bus, this problem would go away. > > We should use another window for 32-bit PCI DMA, and we should enable > > the "monster window" bit, so that devices which are DAC (64-bit) > > address capable don't need to deal with the TLB on the DMA > > controller. We don't currently do either. > > In the first step I would say we should start checking cards for DAC > support and if there are enough of them then do the monster window > thing first. How does DAC fit into busdma? How do we indicate a device is DAC capable to the busdma system? > I asume it's not that critical for >2G machine owners to replace non DAC > cards, especially as I believe many non DAC cards have currently non > busdma drivers as well. Sounds reasonable. > The S/G map can be done later if still required. > Maybe with a tuneable size as a 4G map takes 4M map - checked for 21172. I'm not sure what you're saying. Are you saying that a sparse map can still be effective and we should share with the ISA map if we need to? If so, I agree... Drew
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