Re: [PATCH] sparc32: Page align size in arch_dma_alloc

[Andreas Larsson]

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