• Gavin Shan's avatar
    powerpc/powernv: Override dma_get_required_mask() · fe7e85c6
    Gavin Shan authored
    The dma_get_required_mask() function is used by some drivers to
    query the platform about what DMA mask is needed to cover all of
    memory. This is a bit of a strange semantic when we have to choose
    between IOMMU translation or bypass, but essentially what it means
    is "what DMA mask will give best performances".
    
    Currently, our IOMMU backend always returns a 32-bit mask here, we
    don't do anything special to it when we have bypass available. This
    causes some drivers to choose a 32-bit mask, thus losing the ability
    to use the bypass window, thinking this is more efficient. The problem
    was reported from the driver of following device:
    
    0004:03:00.0 0107: 1000:0087 (rev 05)
    0004:03:00.0 Serial Attached SCSI controller: LSI Logic / Symbios \
                 Logic SAS2308 PCI-Express Fusion-MPT SAS-2 (rev 05)
    
    This patch adds an override of that function in order to, instead,
    return a 64-bit mask whenever a bypass window is available in order
    for drivers to prefer this configuration.
    Reported-by: default avatarMurali N. Iyer <mniyer@us.ibm.com>
    Suggested-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
    Signed-off-by: default avatarGavin Shan <gwshan@linux.vnet.ibm.com>
    Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
    fe7e85c6
pci.c 24.4 KB