[PATCH 07/18] 53c700: improve non-coherent DMA handling

[Thomas Bogendoerfer]

On Tue, Sep 15, 2020 at 05:51:11PM +0200, Christoph Hellwig wrote:
> Switch the 53c700 driver to only use non-coherent descriptor memory if it
> really has to because dma_alloc_coherent fails.  This doesn't matter for
> any of the platforms it runs on currently, but that will change soon.
> 
> To help with this two new helpers to transfer ownership to and from the
> device are added that abstract the syncing of the non-coherent memory.
> The two current bidirectional cases are mapped to transfers to the
> device, as that appears to what they are used for.  Note that for parisc,
> which is the only architecture this driver needs to use non-coherent
> memory on, the direction argument of dma_cache_sync is ignored, so this
> will not change behavior in any way.
> 
> Signed-off-by: Christoph Hellwig <hch at lst.de>
> ---
>  drivers/scsi/53c700.c | 113 +++++++++++++++++++++++-------------------
>  drivers/scsi/53c700.h |  17 ++++---
>  2 files changed, 72 insertions(+), 58 deletions(-)

Tested-by: Thomas Bogendoerfer <tsbogend at alpha.franken.de>

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Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]