On Wed, Jul 09, 2025 at 11:14:37AM -0500, Andrew Davis wrote: > On 7/9/25 7:44 AM, Maxime Ripard wrote: > > Aside from the main CMA region, it can be useful to allow userspace to > > allocate from the other CMA reserved regions. > > > > Indeed, those regions can have specific properties that can be useful to > > a specific us-case. > > > > For example, one of them platform I've been with has ECC enabled on the > > entire memory but for a specific region. Using that region to allocate > > framebuffers can be particular beneficial because enabling the ECC has a > > performance and memory footprint cost. > > > > Thus, exposing these regions as heaps user-space can allocate from and > > import wherever needed allows to cover that use-case. > > > > For now, only shared-dma-pools regions with the reusable property (ie, > > backed by CMA) are supported, but eventually we'll want to support other > > DMA pools types. > > > > Signed-off-by: Maxime Ripard <[email protected]> > > --- > > drivers/dma-buf/heaps/cma_heap.c | 52 > > +++++++++++++++++++++++++++++++++++++++- > > 1 file changed, 51 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/dma-buf/heaps/cma_heap.c > > b/drivers/dma-buf/heaps/cma_heap.c > > index > > 0df007111975447d555714d61ead9699287fd65a..31a18683ee25788a800f3f878fd958718a930ff7 > > 100644 > > --- a/drivers/dma-buf/heaps/cma_heap.c > > +++ b/drivers/dma-buf/heaps/cma_heap.c > > @@ -19,10 +19,12 @@ > > #include <linux/err.h> > > #include <linux/highmem.h> > > #include <linux/io.h> > > #include <linux/mm.h> > > #include <linux/module.h> > > +#include <linux/of.h> > > +#include <linux/of_reserved_mem.h> > > #include <linux/scatterlist.h> > > #include <linux/slab.h> > > #include <linux/vmalloc.h> > > #define DEFAULT_CMA_NAME "default_cma_region" > > @@ -421,7 +423,55 @@ static int __init add_default_cma_heap(void) > > ERR_PTR(ret)); > > } > > return 0; > > } > > -module_init(add_default_cma_heap); > > + > > +static int __init add_cma_heaps(void) > > +{ > > + struct device_node *rmem_node; > > + struct device_node *node; > > + int ret; > > + > > + ret = add_default_cma_heap(); > > Will this double add the default CMA region if it was declared > using DT (reserved-memory) when all those nodes are again scanned > through below? Might need a check in that loop for linux,cma-default.
Yeah, but we probably should anyway. Otherwise, if linux,cma-default
ever change on a platform, we would get heaps appearing/disappearing as
we reboot, which doesn't sound great from a regression perspective.
Both would allocate from the same pool though, so we don't risk stepping
into each others toes. Or am I missing something?
> > + if (ret)
> > + return ret;
> > +
> > + rmem_node = of_find_node_by_path("/reserved-memory");
> > + if (!rmem_node)
> > + goto out;
>
> Can just return here, "out" path doesn't need to put a NULL node.
Oh, right. Thanks!
Maxime
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