Hi syed, thanks for your response. On Fri, Dec 4, 2015 at 9:16 AM, sk.syed2 <sk.syed2@xxxxxxxxx> wrote: >> I have a device with a piece of RAM. That memory is accessible to CPU. >> I write a driver for that device and it maps device memory directly to >> userspace processes. This mapping is cacheable. So far so good. >> > How did you map this device memory? Using ioremap? What platform is this? No, I provide mmap for the device file and then I do remap_pfn_range using vma->vm_pgoff as an offset into the device memory block. That's custom R&D ARM-based thing. >> Now I'd like to flush or invalidate cache on specific parts of that memory. >> If it was just normal system memory I could use streaming DMA API: >> dma_map_*/dma_sync_*/dma_unmap_*. But the device memory is not >> a part of system memory and so there are no struct page for its pages, >> and thus streaming DMA support functions don't work. > > Once you map the io memory, you get VAs for that memory and you should be able > to use dma_sync APIs. I've looked at the following function calls: arm_dma_sync_single_for_cpu -> dma_cache_maint_page -> __dma_page_dev_to_cpu and I see them mapping DMA handle to struct page and using that struct page. I'm sure that will not work, because as I said the device memory is not covered by struct page's. _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
