Re: [PATCH] dma-buf: heaps: Introduce dma_heap_add_cma() for non-default CMA heap

[Kunihiko Hayashi]

Hi John,
Thank you for your comment.

On 2020/07/29 4:17, John Stultz wrote:
> On Thu, Jul 16, 2020 at 6:10 PM Kunihiko Hayashi
> <hayashi.kunihiko@xxxxxxxxxxxxx> wrote:
> > Current dma-buf heaps can handle only default CMA. This introduces
> > dma_heap_add_cma() function to attach CMA heaps that belongs to a device.
> >
> > At first, the driver calls of_reserved_mem_device_init() to set
> > memory-region property associated with reserved-memory defined as CMA
> > to the device. And when the driver calls this dma_heap_add_cma(),
> > the CMA will be added to dma-buf heaps.
> >
> > For example, prepare CMA node named "linux,cma@10000000" and
> > specify the node for memory-region property. After the above calls
> > in the driver, a device file "/dev/dma_heap/linux,cma@10000000"
> > associated with the CMA become available as dma-buf heaps.
> >
> > Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@xxxxxxxxxxxxx>
> > ---
> >   drivers/dma-buf/heaps/cma_heap.c | 12 ++++++++++++
> >   include/linux/dma-heap.h         |  9 +++++++++
> >   2 files changed, 21 insertions(+)
>
> Hey! Sorry for the slow response on this! I just realized I never replied!

I waited but no problem.

> > diff --git a/drivers/dma-buf/heaps/cma_heap.c b/drivers/dma-buf/heaps/cma_heap.c
> > index 626cf7f..5d2442e 100644
> > --- a/drivers/dma-buf/heaps/cma_heap.c
> > +++ b/drivers/dma-buf/heaps/cma_heap.c

[snip]

> > --
> > 2.7.4
>
> Looks sane to me.  Being able to expose different multiple CMA heaps
> is needed, and I agree this way (as opposed to my earlier dts
> appraoch) is probably the best approach. The only bit I'm so-so on is
> adding the CMA heap specific call in the dma-heap.h, but at the same
> time I can't justify adding a whole new header for a single function.

I'm also a little worried about whether "CMA specific" call is in
the dma-heap.h, however I can't find another solution.

> Do you have a upstream driver that you plan to make use this new call?

Unfortunately I don't have an upstream driver using this call.

This call is called from dma-buf heaps "importer" or "customer",
and I only made an example (do nothing) importer driver
to test the call.

> We want to have in-tree users of code added.

I think this is a generic way to use non-default CMA heaps, however,
we need in-tree "importer" drivers to want to use non-default CMA heaps.
I don't find it from now.

> But if so, feel free to add my:
>    Acked-by: John Stultz <john.stultz@xxxxxxxxxx>
> To this patch when you submit the driver changes.

Thank you,

---
Best Regards
Kunihiko Hayashi