On Fri, 3 Jul 2009, Yang Fei-AFY095 wrote: > >> 1. I see dma_cache_maint is called by usb_submit_urb before starting > >> data transfer, > > >It is? Where? > > In drivers/usb/core/hcd.c, usb_hcd_submit_urb -> map_urb_for_dma -> > dma_map_single -> dma_cache_maint. > dma_map_single is defined in arch/arm/include/asm/dma-mapping.h I would have said that dma_map_single, not usb_submit_urb, calls dma_cache_maint. > This is called when we submit urb, for OUT data, I think it's sufficient > for cache consistency. But what I need to know is how we guarantee the > cache consistency for IN data, because the DMA is going to update the > physical memory when receiving data from device, something has to be > done upon completion of the urb. Obviously you looked at map_urb_for_dma. Have you also looked at unmap_urb_for_dma? Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
