Re: [PATCH] au1200fb: don't use DMA_ATTR_NON_CONSISTENT
From: Bartlomiej Zolnierkiewicz
Date: Tue Jul 23 2019 - 11:35:43 EST
On 6/26/19 9:16 AM, Manuel Lauss wrote:
> 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>
Patch queued for v5.4, thanks.
Samsung R&D Institute Poland