Messages in this thread | | | Subject | Re: [PATCH] firewire: Enable physical DMA above 4GB | From | Peter Hurley <> | Date | Fri, 29 Mar 2013 07:31:01 -0400 |
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On Fri, 2013-03-29 at 12:19 +0100, Clemens Ladisch wrote: > Peter Hurley wrote: > > On Fri, 2013-03-29 at 11:44 +0100, Stefan Richter wrote: > >>> On Mar 26 Peter Hurley wrote: > >>>> The FW643e-2 is natively PCIe (not behind a bridge) and supports phys > >>>> DMA past 4GB (the datasheet says all 48 bits but I can only test it out > >>>> to 10GB). > >>>> > >>>> I thought the FW643e was as well? You'll have to test that out :) > >> > >> Does lspci or something similar show which PCI devices are capable of 64 bit > >> wide addressing? > > > > Not definitively. > > > > Usually (but not always), if the host registers are 64-bit addressable, > > then the device supports DAC. > > DACs are a feature of conventional PCI. > > All PCI Express devices are 64-bit addressable. In the lspci output, PCIe > devices have the "Express" capability.
The "device" could be sitting behind a PCIe-PCI bridge that _only_ supports the host window for 64-bit. All other 64-bit decodes could return garbage.
> However, whether a device can *generate* 64-bit DMA requests is completely > device-specific.
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