2010/5/14 Felix Fietkau <nbd@xxxxxxxxxxx>: > On 2010-05-14 3:16 PM, tom.leiming@xxxxxxxxx wrote: >> From: Ming Lei <tom.leiming@xxxxxxxxx> >> >> If buffer is to be accessed by cpu after dma transfer is over, but >> between dma mapping and dma unmapping, we should use >> dma_sync_single_for_cpu to sync the buffer between cpu with >> device. And dma_sync_single_for_device is used to let >> device gain the buffer again. > I think this patch is wrong. On most MIPS devices, > dma_sync_single_for_cpu is a no-op. In fact, with this patch, the rx > path fails very quickly. Sorry for my bad email client. On most MIPS devices, dma_sync_single_for_cpu does same things almost with dma_unmap_single(plat_unmap_dma_mem is no-op). If dma_unmap_single is enough, dma_sync_single_for_cpu is certainly enough, isn't it? For the usage of dma_sync_single_for_cpu or dma_sync_single_for_device, Documentation/DMA-API*.txt give more details. > I believe keeping the dma_sync_single_for_device variant is necessary > for all syncs. Thanks, -- Lei Ming -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
