linux-kernel - Re: powerpc/npu-dma: Remove NPU DMA ops

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Date:   Thu,  8 Nov 2018 08:27:45 +1100 (AEDT)
From:   Michael Ellerman <patch-notifications@...erman.id.au>
To:     Alistair Popple <alistair@...ple.id.au>,
        linuxppc-dev@...ts.ozlabs.org
Cc:     Alistair Popple <alistair@...ple.id.au>, hch@....de,
        linux-kernel@...r.kernel.org
Subject: Re: powerpc/npu-dma: Remove NPU DMA ops

On Tue, 2018-10-30 at 11:02:03 UTC, Alistair Popple wrote:
> The NPU IOMMU is setup to mirror the parent PCIe device IOMMU
> setup. Therefore it does not make sense to call dma operations such as
> dma_map_page, etc. directly on these devices. The existing dma-ops
> simply print a warning if they are ever called, however this is
> unnecessary and the warnings are likely to go unnoticed.
> 
> It is instead simpler to remove these operations and let the generic
> DMA code print warnings (eg. via a NULL pointer deref) in cases of
> buggy drivers attempting dma operations on NVLink devices.
> 
> Signed-off-by: Alistair Popple <alistair@...ple.id.au>

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/3182215dd0b2120fb942ed88430cfb

cheers