Re: [PATCH] au1200fb: don't use DMA_ATTR_NON_CONSISTENT

From: Manuel Lauss
Date: Wed Jun 26 2019 - 03:17:27 EST

On Tue, Jun 25, 2019 at 2:13 PM Christoph Hellwig <hch@xxxxxx> wrote:
> au1200fb allocates DMA memory using DMA_ATTR_NON_CONSISTENT, but never
> calls dma_cache_sync to synchronize the memory between the CPU and the
> device. If it was use on a not cache coherent bus that would be fatal,
> but as far as I can tell from the naming and the mips platform
> implementation it always is used in cache coherent systems. Remove
> the DMA_ATTR_NON_CONSISTENT flag, which is a no-op in that case.

Very early au1200 chips, on which this driver apparently was developed on,
had issues with cache coherency, but this was fixed in a later step,
none of the 3 steppings I have access to exhibit any problems
with this patch applied.

> Signed-off-by: Christoph Hellwig <hch@xxxxxx>

Acked-By: Manuel Lauss <manuel.lauss@xxxxxxxxx>