On Thursday 08 January 2015 14:26:36 Murali Karicheri wrote: > On 01/08/2015 03:40 AM, Arnd Bergmann wrote: > > On Wednesday 07 January 2015 17:37:56 Rob Herring wrote: > >> On Wed, Jan 7, 2015 at 12:49 PM, Murali Karicheri<m-karicheri2@xxxxxx> wrote: > >> > >>> + ret = of_dma_get_range(np,&dma_addr,&paddr,&size); > >>> + if (ret< 0) { > >>> + dma_addr = offset = 0; > >>> + size = dev->coherent_dma_mask + 1; > >> > >> If coherent_dma_mask is DMA_BIT_MASK(64), then you will overflow and > >> have a size of 0. There may also be a problem when the mask is only > >> 32-bit type. > > > > The mask is always a 64-bit type, it's not optional. But you are right, > > the 64-bit mask case is broken, so I guess we have to fix it differently > > by always passing the smaller value into arch_setup_dma_ops and > > adapting that function instead. > Arnd, > > What is the smaller value you are referring to in the below code? > between *dev->dma_mask and size from DT? But overflow can still happen > when size is to be calculated in arch_setup_dma_ops() for Non DT case or > when DT size is configured to be equivalent of DMA_BIT_MASK(64) + 1. Can > we discuss the code change you have in mind when you get a chance? I meant changing every function that the size values gets passed into to take a mask like 0xffffffff instead of a size like 0x100000000, so we can represent a 64-bit capable bus correctly. This means we also need to adapt the value returned from of_dma_get_range. A minor complication here is that the DT properties sometimes already contain the mask value, in particular when we want to represent a full mapping like bus { #address-cells = <1>; #size-cells = <1>; dma-ranges = <0 0 0xffffffff>; /* all 4 GB, DMA_BIT_MASK(32) */ }; as opposed to bus { #address-cells = <1>; #size-cells = <1>; dma-ranges = <0 0 0x80000000>; /* only lower 2GB, DMA_BIT_MASK(31) */ }; or bus { #address-cells = <2>; #size-cells = <2>; dma-ranges = <0 0 0x0000000100000000>; /* 4GB of 64-bit address space */ }; Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html