> Hi Stephan, > > Now I'm implementing Tegra IOMMU, refering to MSM IOMMU, and I don't > understandt what "ctx" means and how it's used in msm iommu. Could you > please clarify a bit about this? > > According to "devices-iommu.c", there seems 12 physical iommu H/Ws, > which represent each platform_device. But there are also 21 > ctx_devices, which are also platform_device. So what's this ctx? Is > thie a client device for an IOMMU h/w? Is this ctx device supposed to > be used with the coming "arm_iommu_attach_device()"? > > Any comment would be readlly appreciated. > > Hiroshi DOYU > Hello The "ctx" devices you are referring to are IOMMU translation context devices. For the purposes of the IOMMU API, these can be thought of as separate and independent IOMMUs, with each context device having its own set of registers (including page table pointer) and having its own address space. Thus, the attach_dev and detach_dev calls would operate on these "ctx" devices rather than the top-level IOMMU devices you mentioned (which don't really interact directly with the IOMMU API). In reality, an IOMMU device can internally contain one or more IOMMU context devices, though some hardware resources do end up being shared between the context devices within the same IOMMU device. This is why there is a parent-child relationship between the IOMMU devices and the context devices - the driver needs to know about and deal with the fact that some internal resources (such as the TLB) may be shared between several context devices within the same IOMMU. I hope this answers your question. Please let me know if you would like me to clarify anything. Steve Sent by an employee of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum. -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
