• J
    firewire: OHCI 1.0 Isochronous Receive support · a186b4a6
    Jarod Wilson 提交于
    Third rendition of FireWire OHCI 1.0 Isochronous Receive support, using a
    zer-copy method similar to OHCI 1.1 which puts the IR data payload directly
    into the userspace buffer. The zero-copy implementation eliminates the
    video artifacts, audio popping, and buffer underrun problems seen with
    version 1 of this patch, as well as fixing a regression in OHCI 1.1 support
    introduced by version 2 of this patch.
    
    Successfully tested in OHCI 1.1 mode on the following chipsets:
    
    - NEC uPD72847 (rev 01), OHCI 1.1 (PCI)
    - Ti XIO2200(A) (rev 01), OHCI 1.1 (PCIe)
    - Ti TSB41AB2 (rev 01), OHCI 1.1 (PCI on SB Audigy)
    - Apple UniNorth 2 (rev 81), OHCI 1.1 (PowerBook G4 onboard)
    
    Successfully tested in OHCI 1.0 mode on the following chipsets:
    
    - Agere FW323 (rev 06), OHCI 1.0 (Mac Mini onboard)
    - Agere FW323 (rev 06), OHCI 1.0 (PCI)
    - Via VT6306 (rev 46), OHCI 1.0 (PCI)
    - NEC OrangeLink (rev 01), OHCI 1.0 (PCI)
    - NEC uPD72847 (rev 01), OHCI 1.1 (PCI)
    - Ti XIO2200(A) (rev 01), OHCI 1.1 (PCIe)
    
    The bulk of testing was done in an x86_64 system, but was also successfully
    sanity-tested on other systems, including a PPC(32) PowerBook G4 and an i686
    EPIA M10k. Crude benchmarking (watching top during capture) puts the cpu
    utilization during capture on the EPIA's 1GHz Via C3 processor around 13%,
    which is down from 30% with the v1 code.
    
    Some implementation details:
    
    To maintain the same userspace API as dual-buffer mode, we set up two
    descriptors for every incoming packet. The first is an INPUT_MORE descriptor,
    pointing to a buffer large enough to hold just the packet's iso headers,
    immediately followed by an INPUT_LAST descriptor, pointing to a chunk of the
    userspace buffer big enough for the packet's data payload. With this setup,
    each incoming packet fills in these two descriptors in a manner that very
    closely emulates dual-buffer receive, to the point where the bulk of the
    handle_ir_* code is now identical between the two (and probably primed for
    some restructuring to share code between them).
    
    The only caveat I have at the moment is that neither of my OHCI 1.0 Via
    VT6307-based FireWire controllers work particularly well with this code
    for reasons I have yet to figure out.
    Signed-off-by: NJarod Wilson <jwilson@redhat.com>
    Signed-off-by: NStefan Richter <stefanr@s5r6.in-berlin.de>
    a186b4a6
fw-ohci.c 58.4 KB