[kernel] powerpc/powernv/ioda2: Reduce upper limit for DMA window size

[Michael Ellerman]

On Fri, 2018-06-01 at 08:06:16 UTC, Alexey Kardashevskiy wrote:
> 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: 7aafac11e3 "powerpc/powernv/ioda2: Gracefully fail if too many TCE levels requested"
> Signed-off-by: Alexey Kardashevskiy <aik at ozlabs.ru>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/d3d4ffaae439981e1e441ebb125aa3

cheers