• Alexey Kardashevskiy's avatar
    powerpc/powernv/ioda2: Reduce upper limit for DMA window size (again) · 7233b8ca
    Alexey Kardashevskiy authored
    mpe: This was fixed originally in commit d3d4ffaa
    ("powerpc/powernv/ioda2: Reduce upper limit for DMA window size"), but
    contrary to what the merge commit says was inadvertently lost by me in
    commit ce57c661 ("Merge branch 'topic/ppc-kvm' into next") which
    brought in changes that moved the code to a new file. So reapply it to
    the new file.
    
    Original commit message follows:
    
    We use PHB in mode1 which uses bit 59 to select a correct DMA window.
    However there is mode2 which uses bits 59:55 and allows up to 32 DMA
    windows per a PE.
    
    Even though documentation does not clearly specify that, it seems that
    the actual hardware does not support bits 59:55 even in mode1, in
    other words we can create a window as big as 1<<58 but DMA simply
    won't work.
    
    This reduces the upper limit from 59 to 55 bits to let the userspace
    know about the hardware limits.
    
    Fixes: ce57c661 ("Merge branch 'topic/ppc-kvm' into next")
    Signed-off-by: default avatarAlexey Kardashevskiy <aik@ozlabs.ru>
    Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
    7233b8ca
pci-ioda-tce.c 9.62 KB