Hi Christoph,
Le mer. 30 sept. 2020 à 11:02, Christoph Hellwig <hch@xxxxxx> a écrit
:
On Mon, Sep 28, 2020 at 03:31:28PM +0200, Paul Cercueil wrote:
It's allocated with dma_alloc_wc, but then it's only accessed as
non-coherent.
Anyway, for the time being I guess you could revert 37054fc81443.
But I
have patches on top of it in drm-misc-next so it's going to be a
mess.
If we have time I can come up with a custom dumb_create() fonction,
to make
sure that the GEM buffers are allocated with
dma_alloc_noncoherent(). Is
there a dma_mmap_noncoherent() too?
Please use the lower-level dma_alloc_pages and then just insert the
pages directly using remap_pfn_range. Although it might make sense
to eventually create a wrapper around remap_pfn_range for all the
vma sizing sanity checks.
One thing missing for remap_pfn_range(), I have no alternative for this:
vma->vm_page_prot = dma_pgprot(dev, vma->vm_page_prot,
DMA_ATTR_NON_CONSISTENT);
So I have to do:
vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
pgprot_val(vma->vm_page_prot) &= ~_CACHE_MASK;
pgprot_val(vma->vm_page_prot) |= _CACHE_CACHABLE_NONCOHERENT;
And that will only compile on MIPS, because these _CACHE_* macros are
only defined there.
I would need something like a pgprot_noncoherent(), I think.
-Paul
