Messages in this thread | | | From | John Stultz <> | Date | Fri, 1 May 2020 12:01:40 -0700 | Subject | Re: [RFC][PATCH 3/4] dma-buf: cma_heap: Extend logic to export CMA regions tagged with "linux,cma-heap" |
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On Fri, May 1, 2020 at 4:08 AM Robin Murphy <robin.murphy@arm.com> wrote: > > On 2020-05-01 11:21 am, Brian Starkey wrote: > > Hi John, > > > > On Fri, May 01, 2020 at 07:39:48AM +0000, John Stultz wrote: > >> This patch reworks the cma_heap initialization so that > >> we expose both the default CMA region and any CMA regions > >> tagged with "linux,cma-heap" in the device-tree. > >> > >> Cc: Rob Herring <robh+dt@kernel.org> > >> Cc: Sumit Semwal <sumit.semwal@linaro.org> > >> Cc: "Andrew F. Davis" <afd@ti.com> > >> Cc: Benjamin Gaignard <benjamin.gaignard@linaro.org> > >> Cc: Liam Mark <lmark@codeaurora.org> > >> Cc: Pratik Patel <pratikp@codeaurora.org> > >> Cc: Laura Abbott <labbott@redhat.com> > >> Cc: Brian Starkey <Brian.Starkey@arm.com> > >> Cc: Chenbo Feng <fengc@google.com> > >> Cc: Alistair Strachan <astrachan@google.com> > >> Cc: Sandeep Patil <sspatil@google.com> > >> Cc: Hridya Valsaraju <hridya@google.com> > >> Cc: Christoph Hellwig <hch@lst.de> > >> Cc: Marek Szyprowski <m.szyprowski@samsung.com> > >> Cc: Robin Murphy <robin.murphy@arm.com> > >> Cc: Andrew Morton <akpm@linux-foundation.org> > >> Cc: devicetree@vger.kernel.org > >> Cc: dri-devel@lists.freedesktop.org > >> Cc: linux-mm@kvack.org > >> Signed-off-by: John Stultz <john.stultz@linaro.org> > >> --- > >> drivers/dma-buf/heaps/cma_heap.c | 18 +++++++++--------- > >> 1 file changed, 9 insertions(+), 9 deletions(-) > >> > >> diff --git a/drivers/dma-buf/heaps/cma_heap.c b/drivers/dma-buf/heaps/cma_heap.c > >> index 626cf7fd033a..dd154e2db101 100644 > >> --- a/drivers/dma-buf/heaps/cma_heap.c > >> +++ b/drivers/dma-buf/heaps/cma_heap.c > >> @@ -141,6 +141,11 @@ static int __add_cma_heap(struct cma *cma, void *data) > >> { > >> struct cma_heap *cma_heap; > >> struct dma_heap_export_info exp_info; > >> + struct cma *default_cma = dev_get_cma_area(NULL); > >> + > >> + /* We only add the default heap and explicitly tagged heaps */ > >> + if (cma != default_cma && !cma_dma_heap_enabled(cma)) > >> + return 0; > > > > Thinking about the pl111 thread[1], I'm wondering if we should also > > let drivers call this directly to expose their CMA pools, even if they > > aren't tagged for dma-heaps in DT. But perhaps that's too close to > > policy. > > That sounds much like what my first thoughts were - apologies if I'm > wildly off-base here, but as far as I understand: > > - Device drivers know whether they have their own "memory-region" or not. > - Device drivers already have to do *something* to participate in dma-buf. > - Device drivers know best how they make use of both the above. > - Therefore couldn't it be left to drivers to choose whether to register > their CMA regions as heaps, without having to mess with DT at all?
I guess I'm not opposed to this. But I guess I'd like to see some more details? You're thinking the pl111 driver would add the "memory-region" node itself?
Assuming that's the case, my only worry is what if that memory-region node isn't a CMA area, but instead something like a carveout? Does the driver need to parse enough of the dt to figure out where to register the region as a heap?
thanks -john
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