• Roland Dreier's avatar
    [POWERPC] Define pci_unmap_addr() et al. when CONFIG_NOT_COHERENT_CACHE=y · 1d4454e7
    Roland Dreier authored
    The current PowerPC code makes pci_unmap_addr(), pci_unmap_addr_set(),
    and friends trivial for all 32-bit kernels.  This is reasonable, since
    for those kernels it is true that pci_unmap_single() does not need the
    DMA address from the original DMA mapping -- in fact, it is a NOP.
    
    However, I recently tried the tg3 driver on a PowerPC 440SPe machine,
    which runs a 32-bit kernel and has non-cache-coherent PCI DMA.  I
    found that the tg3 driver crashed in pci_dma_sync_single_for_cpu(),
    since for non-coherent systems, that function must invalidate the
    cache for the DMA address range requested, and therefore it does use
    the address passed in.  tg3 uses a DMA address it stashes away with
    pci_unmap_addr_set() and retrieves with pci_unmap_addr().  Of course,
    since pci_unmap_addr() is defined to (0) right now, this doesn't work.
    
    It seems to me that the tg3 driver is using pci_unmap_addr() in a
    legitimate way -- I wouldn't want to have to teach all drivers that
    they should use pci_unmap_addr() if they only need the address for
    unmapping functions, but if they want the pci_dma_sync functions, then
    they have to store the DMA address without the helper macros.
    The right fix therefore seems to be in the definition of the macros in
    <asm/pci.h> -- we should use the trivial versions only for 32-bit
    kernels for coherent systems, and the real versions for both 64-bit
    kernels and non-coherent systems.
    Signed-off-by: default avatarRoland Dreier <rolandd@cisco.com>
    Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
    1d4454e7
pci.h 4.53 KB