Messages in this thread | | | From | Rob Herring <> | Date | Fri, 9 Jan 2015 09:34:50 -0600 | Subject | Re: [PATCH v3 2/4] of: move of_dma_configure() to device,c to help re-use |
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On Thu, Jan 8, 2015 at 4:24 PM, Arnd Bergmann <arnd@arndb.de> wrote: > 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@ti.com> 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.
Or you could special case a size of 0 to mean all/max? I'm not sure if we need to handle size=0 for other reasons beyond just wrong DT data.
> 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) */
This is wrong though, right? The DT should be size. Certainly, this could be a valid size, but that would not make the mask 0xfffffffe. We would still want it to be 0xffffffff.
We could do a fixup for these cases adding 1 if bit 0 is set (or not subtracting 1 if we want the mask).
Rob
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