Using CMA with devicetree generated devices

Is it possible to use the devices generated from device tree for use with CMA? The API for reserving a CMA region (dma_declare_contiguous) requires a device pointer to properly associate a region with a device. By the time the devices from devicetree are actually available (generally during machine_init), dma_contiguous_remap has already been called so it's too late to have a properly setup region.

I currently see several options:

1) All CMA devices must be statically declared in the board file
2) Scan the FDT to set up 'dummy' devices early which can later be used to set up CMA with the 'proper' devices
3) My assumption is completely wrong and the check that I was using is invalid:

index 8404601..6d37516 100644
@@ -368,9 +368,11 @@ struct dma_contig_early_reserve {
  static struct dma_contig_early_reserve dma_mmu_remap[MAX_CMA_AREAS] 

__initdata;

static int dma_mmu_remap_num __initdata;
+static int is_remapped;

void __init dma_contiguous_early_fixup(phys_addr_t base, unsigned long
size)
{

+       BUG_ON(is_remapped);
         dma_mmu_remap[dma_mmu_remap_num].base = base;
         dma_mmu_remap[dma_mmu_remap_num].size = size;
         dma_mmu_remap_num++;

@@ -404,6 +406,7 @@ void __init dma_contiguous_remap(void)

                 iotable_init(&map, 1);
         }

+ is_remapped = 1;
}

static void *

I'm currently leaning towards setting up #2 unless I'm missing something obvious here. Thanks.

Laura

Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation

Hello,

dma_declare_contiguous() must be called very early, before any dynamic structures has been created and before core memory management subsystem has been set up. IMHO it should be possible to add support for DT directly in drivers/base/dma-contiguous.c. CMA code can iterate over DT nodes to initialize its internal structures and then use them once the DT devices are being probed/set-up.

Best regards

Marek Szyprowski
Samsung Poland R&D Center