On Fri, Dec 25, 2020 at 08:18:14AM +0000, Noam Liron wrote: > Hi All, > > I am working on LK 4.14.76, on a SOC in which RAM starts at 0x200000000, and need to limit DMA buffer allocations to be below 0x220000000. > I planned to do it by setting dma_mask to 0x21FFFFFFF. > > But in drivers/usb/core/usb.c:590 I see the following: > Note: calling dma_set_mask() on a USB device would set the > mask for the entire HCD, so don't do that. > > I also found related message: > https://marc.info/?l=linux-usb&m=160023769800697&w=2 : "... as the dma_mask is set by default for most busses". > > So how can I set properly the dma_mask? Your USB host controller device sets that up properly, no need to do it for any individual USB device. I think the resources that the controller gets assigned for this should handle it for you. greg k-h > >
