On 10/16/20 11:23 AM, Arnd Bergmann wrote: > On Fri, Oct 16, 2020 at 6:48 PM Florian Fainelli <f.fainelli@xxxxxxxxx> wrote: >> On 10/16/20 4:01 AM, Arnd Bergmann wrote: >>> On Fri, Oct 16, 2020 at 11:09 AM Zhen Lei <thunder.leizhen@xxxxxxxxxx> wrote: >>>> >>>> Suggested-by: Arnd Bergmann <arnd@xxxxxxxx> >>>> Signed-off-by: Zhen Lei <thunder.leizhen@xxxxxxxxxx> >>> >>> Acked-by: Arnd Bergmann <arnd@xxxxxxxx> >>> >>> I see that at least the 'bcd' and 'xhci' devices in fact try to >>> use 64-bit DMA. It would be good to test this on actual >>> hardware to ensure that it works correctly when this is enabled. >>> >>> Ideally avoiding the swiotlb bounce buffering should only >>> make it faster here, but there are many chips on which >>> 64-bit DMA is broken in some form. >> >> Is this change really an improvement though? This 'usb' pseudo bus node >> could just keep being defined with #address-cells = <1> and #size-cells >> = <1> so as to satisfy the 'reg' definition however we could just adjust >> dma-ranges to indicate full 64-bit addressing capability. Would not that >> work? > > When #address-cells is '1', you cannot specify dma-ranges that > go beyond a 32-bit address range. Would not it be enough to remove the 'dma-ranges' property though? Sorry for being slow here. -- Florian
