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SubjectRe: linux-next: build failure after merge of the drm tree


Le mer. 30 sept. 2020 à 18:40, Christoph Hellwig <hch@lst.de> a écrit
:
> On Wed, Sep 30, 2020 at 06:39:18PM +0200, Paul Cercueil wrote:
>>> dma_alloc_pages gives you cached memory, so you can't just use an
>>> uncached protection for the userspace mmap here. If you want
>>> uncached
>>> memory you need to use dma_alloc_coherent paired with
>>> dma_mmap_coherent.
>>> Or dma_alloc_wc for a slightly different flavor of uncached. (both
>>> of the map to dma_alloc_attrs / dma_mmap_attrs eventually).
>>
>> I don't want uncached memory, I want non-coherent cached memory.
>
> We don't have such a thing in the Linux API at all.

dma_pgprot(dev, vma->vm_page_prot, DMA_ATTR_NON_CONSISTENT);

That was giving me non-coherent cached memory, and now I don't have an
alternative.

-Paul


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