[PATCH v4 7/7] dma-buf: system_heap: Add a system-uncached heap re-using the system heap

[Hillf Danton]

On Thu, 29 Oct 2020 15:28:34 -0700 John Stultz wrote:
> On Thu, Oct 29, 2020 at 12:10 AM Hillf Danton <hdanton at sina.com> wrote:
> > On Thu, 29 Oct 2020 00:16:24 +0000 John Stultz wrote:
> > > @@ -194,6 +210,9 @@ static int system_heap_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma)
> > >       struct sg_page_iter piter;
> > >       int ret;
> > >
> > > +     if (buffer->uncached)
> > > +             vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
> > > +
> >
> > Wonder why you turn back to dma_mmap_wc() and friends?
> 
> Sorry, can you expand on what you are proposing here instead?  I'm not
> sure I see how dma_alloc/mmap/*_wc() quite fits here.

I just wondered if *_wc() could save you two minutes or three. Can you
shed some light on your concerns about their unfitness?