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From: Andreas Larsson <andreas@gaisler.com>
To: Christoph Hellwig <hch@lst.de>
Cc: David Miller <davem@davemloft.net>,
	sparclinux@vger.kernel.org, Sam Ravnborg <sam@ravnborg.org>,
	linux-kernel@vger.kernel.org, software@gaisler.com
Subject: Re: [PATCH] sparc32: Page align size in arch_dma_alloc
Date: Tue, 14 Sep 2021 10:51:51 +0200	[thread overview]
Message-ID: <87971ad4-9519-cf0d-76a8-6baa253d0122@gaisler.com> (raw)
In-Reply-To: <20210914061705.GB26679@lst.de>

On 2021-09-14 08:17, Christoph Hellwig wrote:
> Thanks.  Can you take a look and test the two patches below on top of
> your fix?  A git tree is also available here:
> 
> http://git.infradead.org/users/hch/misc.git/shortlog/refs/heads/sparc32-generic-dma
> 

In a quick test, this seems to work on LEON for code paths previously 
going to arch_dma_alloc and arch_dma_free. However, this makes setting 
up these DMA mappings to not go through sparc_dma_alloc_resource, and it 
seems important that they do that on Sun systems. Hopefully, someone 
with more knowledge about that could chime in here.

The added pgprot_dmacoherent is problematic as it sets SRMMU_PRIV, which 
sets up kernel access only. This was fine for arch_dma_alloc that sets 
up kernel accesses only, but for user space DMA mmap this would make 
them kernel accessable only. Having no sparc-specific 
pgprot_dmacoherent, keeping it to default to pgprot_noncached, is 
probably better.

-- 
Andreas Larsson

  reply	other threads:[~2021-09-14  8:51 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-08  7:48 [PATCH] sparc32: Page align size in arch_dma_alloc Andreas Larsson
2021-09-09  6:07 ` Christoph Hellwig
2021-09-13 13:18   ` Andreas Larsson
2021-09-14  6:17     ` Christoph Hellwig
2021-09-14  8:51       ` Andreas Larsson [this message]
2021-09-14 10:42         ` Christoph Hellwig
2021-09-14 11:16           ` Andreas Larsson
2021-09-14 11:26             ` Christoph Hellwig
     [not found] ` <YTjfJl6YmBCdZ8XB@ravnborg.org>
2021-09-14  6:12   ` Christoph Hellwig
2021-09-14 11:39     ` David Miller

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