> > > > Robin, have you looked into supporting multiple dma-ranges? It's the > > > > next thing > > > > we need for BCM STB's PCIe. I'll have a go at it myself if nothing is in > > > > the > > > > works already. > > > > > > Multiple dma-ranges as far as configuring inbound windows should work > > > already other than the bug when there's any parent translation. But if > > > you mean supporting multiple DMA offsets and masks per device in the > > > DMA API, there's nothing in the works yet. Sorry, I meant supporting multiple DMA offsets[1]. I think I could still make it with a single DMA mask though. > > There's also the in-between step of making of_dma_get_range() return a > > size based on all the dma-ranges entries rather than only the first one > > - otherwise, something like [1] can lead to pretty unworkable default > > masks. We implemented that when doing acpi_dma_get_range(), it's just > > that the OF counterpart never caught up. > > Right. I suppose we assume any holes in the ranges are addressable by > the device but won't get used for other reasons (such as no memory > there). However, to be correct, the range of the dma offset plus mask > would need to be within the min start and max end addresses. IOW, > while we need to round up (0xa_8000_0000 - 0x2c1c_0000) to the next > power of 2, the 'correct' thing to do is round down. IIUC I also have this issue on my list. The RPi4 PCIe block has an integration bug that only allows DMA to the lower 3GB. With dma-ranges of size 0xc000_0000 you get a 32bit DMA mask wich is not what you need. So far I faked it in the device-tree but I guess it be better to add an extra check in of_dma_configure(), decrease the mask and print some kind of warning stating that DMA addressing is suboptimal. Regards, Nicolas [1] https://lkml.org/lkml/2018/9/19/641
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