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Also document how the selected BAR may be shared > with an MW. > > Signed-off-by: Koichiro Den > --- Reviewed-by: Frank Li > Changes since v5: > - No changes. > > Documentation/PCI/endpoint/pci-vntb-howto.rst | 31 +++++++++++++++++-- > 1 file changed, 28 insertions(+), 3 deletions(-) > > diff --git a/Documentation/PCI/endpoint/pci-vntb-howto.rst b/Documentation/PCI/endpoint/pci-vntb-howto.rst > index 3679f5c30254..7ca4e1ff095c 100644 > --- a/Documentation/PCI/endpoint/pci-vntb-howto.rst > +++ b/Documentation/PCI/endpoint/pci-vntb-howto.rst > @@ -90,9 +90,9 @@ of the function device and is populated with the following NTB specific > attributes that can be configured by the user:: > > # ls functions/pci_epf_vntb/func1/pci_epf_vntb.0/ > - ctrl_bar db_count mw1_bar mw2_bar mw3_bar mw4_bar spad_count > - db_bar mw1 mw2 mw3 mw4 num_mws vbus_number > - vntb_vid vntb_pid > + ctrl_bar dma_bar mw2 mw3_bar num_mws vntb_pid > + db_bar mw1 mw2_bar mw4 spad_count vntb_vid > + db_count mw1_bar mw3 mw4_bar vbus_number > > A sample configuration for NTB function is given below:: > > @@ -105,6 +105,31 @@ By default, each construct is assigned a BAR, as needed and in order. > Should a specific BAR setup be required by the platform, BAR may be assigned > to each construct using the related ``XYZ_bar`` entry. > > +To export DMA channels, set ``dma_bar`` before binding the function. > +For example:: > + > + # echo 5 > functions/pci_epf_vntb/func1/pci_epf_vntb.0/dma_bar > + > +This currently supports the unrolled DesignWare eDMA layout. The EPC must > +support subrange and dynamic inbound mappings. > + > +``dma_bar`` cannot select the control or doorbell BAR. > +Any rounded-up BAR tail is scratch-backed. > + > +Leaving ``dma_bar`` unassigned disables DMA export. > +With a separate DMA BAR, an older ``ntb_hw_epf`` peer can ignore the extension > +and continue without DMA. A peer that understands the extension also continues > +without DMA if the advertised type is unavailable or no DMA IRQ can be > +allocated. > + > +If no spare BAR is available, ``dma_bar`` can select the BAR of one MW instead. > +DMA resources then follow that MW. In this configuration: > + > +* The shared MW size must be a power of two and its translation must cover the > + full configured size. > +* An updated peer is required because older peers treat the whole BAR as an > + MW. > + > A sample configuration for virtual NTB driver for virtual PCI bus:: > > # echo 0x1957 > functions/pci_epf_vntb/func1/pci_epf_vntb.0/vntb_vid > -- > 2.54.0 >