Messages in this thread | | | Date | Thu, 9 May 2024 13:54:56 +0100 | Subject | Re: [PATCH] dma-direct: Set SG_DMA_SWIOTLB flag for dma-direct | From | Robin Murphy <> |
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On 08/05/2024 12:33 pm, Christoph Hellwig wrote: > On Tue, May 07, 2024 at 01:07:25PM -0700, T.J. Mercier wrote: >> On Mon, May 6, 2024 at 10:43???PM Christoph Hellwig <hch@lst.de> wrote: >>> >>> On Mon, May 06, 2024 at 09:39:53AM -0700, T.J. Mercier wrote: >>>>> You should not check, you simply must handle it by doing the proper >>>>> DMA API based ownership management. >>>> >>>> That doesn't really work for uncached buffers. >>> >>> What uncached buffers? >> >> For example these ones: >> https://android.googlesource.com/kernel/common/+/refs/heads/android-mainline/drivers/dma-buf/heaps/system_heap.c#141 > > Whatever that code is doing is probably not upstream because it's too > broken to live.
Indeed, at a glance it appears to be trying to reinvent dma_alloc_noncontiguous(). What's not immediately obvious is whether it's particular about allocations being DMA-contiguous; if not then I think it comes down to the same thing as vb2-dma-sg and the ideas we were tossing around for that[1].
Thanks, Robin.
[1] https://lore.kernel.org/linux-media/20231228074645.765yytb2a7hvz7ti@chromium.org/
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