On 09/20/2012 12:40 AM, Krishna Reddy wrote: >>> On Tegra, the following use cases need specific IOVA mapping. >>> 1. Few MMIO blocks need IOVA=PA mapping setup. >> >> In that case, why would we enable the IOMMU for that one device; IOMMU >> disabled means VA==PA, right? Perhaps isolation of the device so it can only >> access certain PA ranges for security? > > The device(H/W controller) need to access few special memory blocks(IOVA==PA) > and DRAM as well. OK, so only /some/ of the VA space is VA==PA, and some is remapped; that's a little different that what you originally implied above. BTW, which HW module is this; AVP/COP or something else. This sounds like an odd requirement. > There is also a case where frame buffer memory is passed from BootLoader to Kernel and > display H/W continues to access it with IOMMU enabled. To support this, the one to one > mapping has to be setup before enabling IOMMU. Yes, that makes sense. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>