Messages in this thread | | | From | Rob Herring <> | Date | Fri, 15 Apr 2016 10:59:07 -0500 | Subject | Re: [PATCH 1/2] [v4] net: emac: emac gigabit ethernet controller driver |
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On Fri, Apr 15, 2016 at 10:44 AM, Timur Tabi <timur@codeaurora.org> wrote: > Rob Herring wrote: >>> >>> > >>> > dma-mask = <0 0xffffffff>; >>> > >>> >or >>> > >>> > dma-mask = <0xffffffff 0xffffffff>; >> >> No. See dma-ranges. > > > How exactly should I use dma-ranges? I can't find any other drivers that > queries that property and uses the result to call dma_set_mask. I thought > the dma-ranges property is intended to specify address translation. I don't > need to translate any address, I just need to know a single number.
You may only care about the size, but the binding has to handle the more complex case. Here's an example
<0x0 0x2 0x0 0x1 0x0>
dma address 0 (cell 0) maps to cpu (parent) address 0x2_00000000 (cell 1-2) and the range/size is 4G (cell 3-4).
If you have the same base address, then use the same address. The core will calculate the mask based on the size. IIRC, we also handle ~0 as a special case to support 4G for #size-cell=1.
Rob
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