> -----Original Message----- > From: Hiroshi Doyu [mailto:hdoyu@xxxxxxxxxx] > Sent: Tuesday, August 19, 2014 4:33 PM > To: Sethi Varun-B16395; Will Deacon > Cc: Hiroshi Doyu; Thierry Reding; Stephen Warren; Arnd Bergmann; Mark > Rutland; devicetree@xxxxxxxxxxxxxxx; Olof Johansson; iommu@lists.linux- > foundation.org; Rob Herring; linux-tegra@xxxxxxxxxxxxxxx; linux-arm- > kernel@xxxxxxxxxxxxxxxxxxx; Yoder Stuart-B08248 > Subject: Re: [PATCH v5] devicetree: Add generic IOMMU device tree bindings > > > Varun Sethi <Varun.Sethi@xxxxxxxxxxxxx> writes: > > >> >> > Also, for dynamic stream ID allocation we would need to > >> >> > represent the specific master register (to store the stream ID) in the > device tree. > >> >> > >> >> I assmue that the above means that iMX has such configuration > >> >> register to map steramID and a device dynamically. > >> > > >> > We have per master registers for setting the stream ID on the > >> > Layerscape platforms. My point was that we would need the iommu > >> > master node to include a reference to the master id register. > >> > > >> > master@1 { > >> > /* device has master ID 42 in the IOMMU */ > >> > iommus = <&{/iommu} 42>; > >> > master-id-reg = <phandle offset> }; > >> > >> In the above, for "iommus=" bindings, you wouldn't need to break > >> ARM,SMMU compatibility at all if you set "streamID" exactly as below. > >> > >> master@1 { > >> /* device has master ID 42 in the IOMMU */ > >> iommus = <&{/iommu} 'any given streamID'>; > >> master-id-reg = <phandle offset> > >> }; > >> > >> And your SoC needs to register bus_notifier and ADD_DEVICE should > >> configure to map 'any given streamID' to a device via the above > >> register. This wouldn't need any modification from ARM,SMMU driver > >> and keep the iommus bindings as it is. > >> > >> IOW, SoC only needs to register ADD_DEVICE in bus_notifier to map > >> StreamID to a device. This needs to be executed earlier than IOMMU > >> bus's ADD_DEVICE, though. > >> > >> Is my understanding right? > > > > I don't think that SOC specific code needs a bus notifier for setting > > the stream ID. It can be done as a part of SOC specific > > initialization. The device tree can be updated to reflect the correct > > stream ID (SMMU driver can get the updated stream ID from device > > tree). > > That's possible. > > > I was thinking more on the lines of updating the device stream id > > while attaching a device to the domain. > > I thought the same but this would break the ARM,SMMU /compatibility/ since > the 1st param of "iommus=" is always expected as "streamID". > > If streamID can be assigned dynamically like PCIe, not like streamID statically > set in DT, how should we describe this dynmaic steramID shifting/assignment in > DT? Can you dynamically program the stream ID for the device? If yes, then you require a unique numberspace for allocating a streamID. I am not clear on the stream ID translation requirement. -Varun -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
