On Wed, Nov 4, 2009 at 2:47 PM, Luis R. Rodriguez <mcgrof@xxxxxxxxx> wrote: > On Wed, Nov 4, 2009 at 2:45 PM, Luis R. Rodriguez <mcgrof@xxxxxxxxx> wrote: >> On Wed, Nov 4, 2009 at 2:31 PM, Nick Kossifidis <mickflemm@xxxxxxxxx> wrote: >>> 2009/11/5 Luis R. Rodriguez <mcgrof@xxxxxxxxxxxxxxxxxxxxxx>: >>>> On Wed, Nov 04, 2009 at 02:04:11PM -0800, Luis R. Rodriguez wrote: >>>>> On Wed, Nov 4, 2009 at 2:00 PM, Matthew Wilcox <matthew@xxxxxx> wrote: >>>>> > On Wed, Nov 04, 2009 at 01:52:30PM -0800, Luis R. Rodriguez wrote: >>>>> >> > Even better: I just confirmation from our systems team that our legacy >>>>> >> > devices and 11n PCI devices don't support MWR so I'll remove all that >>>>> >> > cruft crap. >>>>> >> >>>>> >> I meant MWI of course. >>>>> > >>>>> > Yes, but they don't necessarily just use cacheline size for MWI ... some >>>>> > devices use cacheline size for setting up data structures. Might be >>>>> > worth just checking explicitly that they don't use the cacheline size >>>>> > register for anything. >>>>> >>>>> Oh right -- so the typical Atheros hack for this is to check the cache >>>>> line size, and if its 0 set it to L1_CACHE_BYTES. Then eventually read >>>>> from PCI_CACHE_LINE_SIZE pci config to align the skb data. So what I >>>>> was doing now is removing all this cruft and replacing it with a >>>>> generic allocator for atheros drivers that aligns simply to the >>>>> L1_CACHE_BYTES. Sound kosher? >>>> >>>> Something like this: >>>> >>> >>> According to comments inside MadWiFi AR5210 needs cache line align >>> else we get corruptions. >> >> For what though? >> >>> I don't know if this is correct for all >>> platforms or later cards but since we (plan to) support AR5210 i guess >>> we should leave it there. We need to test this a lot on various >>> archs/cards before applying it. >> >> There are two cases where we can use the PCI_CACHE_LINE_SIZE: >> >> 1) Hardware has been designed to use it on some block to align some data somehow >> 2) Software uses it to align skb->data for performance/hw purposes >> >> I believe the second case can be handled by using L1_CACHE_BYTES >> instead and I'd at least like to change our common skb allocator to >> use that. >> >> The first case is where it seems there may be some skepticism as to >> whether or not hw really did not rely on it and I agree its safer to >> keep the programming of the PCI_CACHE_LINE_SIZE in case it has a >> bogus value. >> >> Does this seem reasonable? > > I guess we can keep the second case allocator which relies on > PCI_CACHE_LINE_SIZE, but if so then USB will just define its own csz > statically always to L1_CACHE_BYTES which is fine too -- I was just > hoping we could remove the PCI_CACHE_LINE_SIZE programming completely > too and use a simple L1_CACHE_BYTES aligned allocator. OK I'll leave all this crap and just annotate why its there. Right now its just voodoo. Luis -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
