powerpc/powernv/ioda2: Reduce upper limit for DMA window size (again)
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: Alexey Kardashevskiy <aik@ozlabs.ru> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
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