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

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Date:   Tue, 22 Sep 2020 10:49:34 +0200
From:   Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To:     Christoph Hellwig <hch@....de>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
        Joonyoung Shim <jy0922.shim@...sung.com>,
        Seung-Woo Kim <sw0312.kim@...sung.com>,
        Ben Skeggs <bskeggs@...hat.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Tomasz Figa <tfiga@...omium.org>,
        Matt Porter <mporter@...nel.crashing.org>,
        iommu@...ts.linux-foundation.org,
        Stefan Richter <stefanr@...6.in-berlin.de>,
        linux1394-devel@...ts.sourceforge.net, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-mips@...r.kernel.org,
        linux-parisc@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
        nouveau@...ts.freedesktop.org, netdev@...r.kernel.org,
        linux-scsi@...r.kernel.org, linux-mm@...ck.org,
        alsa-devel@...a-project.org
Subject: Re: [PATCH 07/18] 53c700: improve non-coherent DMA handling

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@....de>
> ---
>  drivers/scsi/53c700.c | 113 +++++++++++++++++++++++-------------------
>  drivers/scsi/53c700.h |  17 ++++---
>  2 files changed, 72 insertions(+), 58 deletions(-)

Tested-by: Thomas Bogendoerfer <tsbogend@...ha.franken.de>

-- 
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