On Wed, Jul 17, 2019 at 05:31:34PM +0200, Nicolas Saenz Julienne wrote: > Historically devices with ZONE_DMA32 have been assumed to be able to > address at least the lower 4GB of ram for DMA. This is still the defualt > behavior yet the Raspberry Pi 4 is limited to the first GB of memory. > This has been observed to trigger failures in dma_direct_supported() as > the 'min_mask' isn't properly set. > > We create 'dma_direct_min_mask' in order for the arch init code to be > able to fine-tune dma direct's 'min_dma' mask.
Normally we use ZONE_DMA for that case.
