Hello Hillf,
On Mon, Aug 19, 2019 at 12:38:38AM +0200, Tobias Klausmann wrote:
>
> On 18.08.19 05:13, Hillf Danton wrote:
> > On Sat, 17 Aug 2019 00:42:48 +0200 Tobias Klausmann wrote:
> > > Hi Nicolin,
> > >
> > > On 17.08.19 00:25, Nicolin Chen wrote:
> > > > Hi Tobias
> > > >
> > > > On Fri, Aug 16, 2019 at 10:16:45PM +0200, Tobias Klausmann wrote:
> > > > > > do you have CONFIG_DMA_CMA set in your config? If not please make
> > > > > > sure
> > > > > > you have this commit in your testing tree, and if the problem still
> > > > > > persists it would be a little odd and we'd have to dig deeper:
> > > > > >
> > > > > > commit dd3dcede9fa0a0b661ac1f24843f4a1b1317fdb6
> > > > > > Author: Nicolin Chen <nicoleots...@gmail.com>
> > > > > > Date: Wed May 29 17:54:25 2019 -0700
> > > > > >
> > > > > > dma-contiguous: fix !CONFIG_DMA_CMA version of dma_{alloc,
> > > > > > free}_contiguous()
> > > > > yes CONFIG_DMA_CMA is set (=y, see attached config), the commit you
> > > > > mention
> > > > > above is included, if you have any hints how to go forward, please
> > > > > let me
> > > > > know!
> > > > For CONFIG_DMA_CMA=y, by judging the log with error code -12, I
> > > > feel this one should work for you. Would you please check if it
> > > > is included or try it out otherwise?
> > > >
> > > > dma-contiguous: do not overwrite align in dma_alloc_contiguous()
> > > > https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=c6622a425acd1d2f3a443cd39b490a8777b622d7
> > >
> > > Thanks for the hint, yet the commit is included and does not fix the
> > > problem!
> > >
> Hi Hillf,
>
> i just tested you first hunk (which comes from kernel/dma/direct.c if i'm
> not mistaken), it did not compile on its own, yet with a tiny bit of work it
> did, and it does indeed solve the regression. But if using that is the
> "right" way to do it, not sure, but its not on me to decide.
>
> Anyway: Thanks for the hint,
>
> Tobias
>
>
> > Hi Tobias
> >
> > Two minor diffs below in hope that they might make sense.
> >
> > 1, fallback unless dma coherent ok.
> >
> > --- a/kernel/dma/contiguous.c
> > +++ b/kernel/dma/contiguous.c
> > @@ -246,6 +246,10 @@ struct page *dma_alloc_contiguous(struct
> > size_t cma_align = min_t(size_t, align, CONFIG_CMA_ALIGNMENT);
> > page = cma_alloc(cma, count, cma_align, gfp & __GFP_NOWARN);
> > + if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
> > + dma_free_contiguous(dev, page, size);
> > + page = NULL;
> > + }
Right...the condition was in-between. However, not every caller
of dma_alloc_contiguous() is supposed to have a coherent check.
So we either add a 'bool coherent_ok' to the API or revert the
dma-direct part back to the original. Probably former option is
better?
Thank you for the debugging. I have been a bit distracted, may
not be able to submit a fix very soon. Would you like to help?
Thanks!
Nicolin
> > }
> > /* Fallback allocation of normal pages */
> > --
> >
> > 2, cleanup: cma unless contiguous
> >
> > --- a/kernel/dma/contiguous.c
> > +++ b/kernel/dma/contiguous.c
> > @@ -234,18 +234,13 @@ struct page *dma_alloc_contiguous(struct
> > size_t count = PAGE_ALIGN(size) >> PAGE_SHIFT;
> > size_t align = get_order(PAGE_ALIGN(size));
> > struct page *page = NULL;
> > - struct cma *cma = NULL;
> > -
> > - if (dev && dev->cma_area)
> > - cma = dev->cma_area;
> > - else if (count > 1)
> > - cma = dma_contiguous_default_area;
> > /* CMA can be used only in the context which permits sleeping */
> > - if (cma && gfpflags_allow_blocking(gfp)) {
> > + if (count > 1 && gfpflags_allow_blocking(gfp)) {
> > size_t cma_align = min_t(size_t, align, CONFIG_CMA_ALIGNMENT);
> > - page = cma_alloc(cma, count, cma_align, gfp & __GFP_NOWARN);
> > + page = cma_alloc(dev_get_cma_area(dev), count, cma_align,
> > + gfp & __GFP_NOWARN);
> > if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
> > dma_free_contiguous(dev, page, size);
> > page = NULL;
> > --
> >
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