From mboxrd@z Thu Jan 1 00:00:00 1970 From: mike.looijmans@topic.nl (Mike Looijmans) Date: Thu, 7 May 2015 15:31:03 +0200 Subject: dma_alloc_coherent versus streaming DMA, neither works satisfactory In-Reply-To: References: <5538DD02.6050401@topic.nl> <3382997.5hgfVKmNXP@wuerfel> <5540D356.50708@topic.nl> <9622793.RaVBbeJMCx@wuerfel> <554B49F0.1090100@topic.nl> Message-ID: <554B6917.40705@topic.nl> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org ?On 07-05-15 15:21, Daniel Drake wrote: > On Thu, May 7, 2015 at 5:18 AM, Mike Looijmans wrote: >> I reverted all my patches and workarounds. Indeed, the kernel needs a >> "coherent" version of the dma_mmap routine, as the current version will map >> it as non-cachable, resulting in a big performance hit (and nullifying the >> whole idea behind it). >> >> I'll test it further on my 'hardware' and cook up a patch that correctly >> maps the coherent pages. > > Sorry that I have only read this thread briefly, but I wonder if this > is what you are looking for: > http://lists.infradead.org/pipermail/linux-arm-kernel/2015-February/325489.html It's related, but targets another use case. This one does the same in case the driver requested non-consistent memory. My use case was that I have hardware implemented coherency (through ACP) so the CPU's and device's view on memory is already consistent, regardless of the status of the cache. The patches are complimentary, not overlapping. Thanks for the link though, it's something I was also looking into, as I don't always need coherency. Kind regards, Mike Looijmans System Expert TOPIC Embedded Products Eindhovenseweg 32-C, NL-5683 KH Best Postbus 440, NL-5680 AK Best Telefoon: +31 (0) 499 33 69 79 Telefax: +31 (0) 499 33 69 70 E-mail: mike.looijmans at topicproducts.com Website: www.topicproducts.com Please consider the environment before printing this e-mail