On Thu, 17 Mar 2016 23:50:20 +0000 Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> wrote: > On Thu, Mar 17, 2016 at 07:17:24PM -0400, okaya@xxxxxxxxxxxxxx wrote: > > What is the correct way? I don't want to write engine->sram_dma = sram > > Well, what the driver _is_ wanting to do is to go from a CPU physical > address to a device DMA address. phys_to_dma() looks like the correct > thing there to me, but I guess that's just an offset and doesn't take > account of any IOMMU that may be in the way. > > If you have an IOMMU, then the whole phys_to_dma() thing is a total > failure as it only does a linear translation, and there are no > interfaces in the kernel to take account of an IOMMU in the way. So, > it needs something designed for the job, implemented and discussed by > the normal methods of proposing a new cross-arch interface for drivers > to use. > > What I'm certain of, though, is that the change proposed in this patch > will break current users of this driver: virt_to_page() on an address > returned by ioremap() is completely undefined, and will result in > either a kernel oops, or if not poking at memory which isn't a struct > page, ultimately resulting in something that isn't SRAM being pointed > to by "engine->sram_dma". > Or we could just do engine->sram_dma = res->start; which is pretty much what the SRAM/genalloc code is doing already. -- Boris Brezillon, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
