On Fri, May 1, 2020 at 4:08 AM Robin Murphy <[email protected]> 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 <[email protected]> > >> Cc: Sumit Semwal <[email protected]> > >> Cc: "Andrew F. Davis" <[email protected]> > >> Cc: Benjamin Gaignard <[email protected]> > >> Cc: Liam Mark <[email protected]> > >> Cc: Pratik Patel <[email protected]> > >> Cc: Laura Abbott <[email protected]> > >> Cc: Brian Starkey <[email protected]> > >> Cc: Chenbo Feng <[email protected]> > >> Cc: Alistair Strachan <[email protected]> > >> Cc: Sandeep Patil <[email protected]> > >> Cc: Hridya Valsaraju <[email protected]> > >> Cc: Christoph Hellwig <[email protected]> > >> Cc: Marek Szyprowski <[email protected]> > >> Cc: Robin Murphy <[email protected]> > >> Cc: Andrew Morton <[email protected]> > >> Cc: [email protected] > >> Cc: [email protected] > >> Cc: [email protected] > >> Signed-off-by: John Stultz <[email protected]> > >> --- > >> 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
