On 11/13/2013 11:41 PM, Hiroshi Doyu wrote: > Stephen Warren <swarren@xxxxxxxxxxxxx> wrote @ Wed, 13 Nov 2013 18:58:23 +0100: > >>> smmu: iommu@xxxxxx { >>> #iommu-cells = <3>; >>> ^^^^^^^^^^^^^^^^^^ >>> }; >>> >>> host1x { >>> compatible = "nvidia,tegra30-host1x", "simple-bus"; >>> iommu = <&smmu 0x??????? 0x??????? "asid">; >>> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^####### >>> gr3d { >>> compatible = "nvidia,tegra30-gr3d"; >>> iommu = <&smmu 0x??????? 0x???????>; >>> } >>> >>> I think that this "asid" part can be set 0 in tegra??.dtsi and the >>> actual value can be overwritten in tegra??-<boardname>.dts file. >> >> The one issue here is that we can only override entire properties, so >> it's not possible for a board file to *just* replace the ASID, it'd have >> to duplicate the entire property, just to change the one value. >> >> Is the ASID mapping really likely to be board-specific though? To my >> naive thinking, it seems that the chip design (e.g. number of >> peripherals, number of available ASIDs) would tend to imply the >> device->ASID mapping, since it would have been considered as part of >> chip design. Hence, wouldn't soc.dtsi typically specify the expected >> ASID mapping, and boards rarely if ever override it? >> >> If the ASID mapping really is likely to vary per board, perhaps it makes >> sense to put it into a separate property somehow so it's easier to override? > > Older Tegra like T30: swgroups > asid(==4) > Newer Tegra : swgroups < asid In that case, I'd vote for hard-coding the mapping in the driver in all cases. For older Tegra, we'll have to hard-code some static mapping just like you've already done in the driver. For newer Tegra, we would just assign a new AS for each swgroup as you say. If we ever need to tweak this, we can invent a new DT property to affect the default. That makes the DT content quite a bit simpler for now:-) -- 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