I believe this might be a case of cache coherency, since you are using the same buffer to DMA as well as allowing it to be cached. Thanks, Satish
________________________________ From: [email protected] [mailto:[email protected]] On Behalf Of Nitin Joshi Sent: Tuesday, February 24, 2009 12:46 PM To: [email protected] Subject: [EDMA help required] DM6446: From AEMIF to DDR memory Hi all, I need some help in EDMA transfer from AEMIF to DDR memory on DM6446. Details: I have a FPGA(16 bit interface) connected to AEMIF(CS4). I have to read 5 times, 500 words(16bit) each from my application. I have written a small char driver to do the DMA read operation. Problem: DMA transfer is done for first 500 words and from next time onwards DMA transfer will miss the data in chunks ok 16 or 32 words. i.e say I have application code - /**********application code **********/ - Open the device then for(i=0;i<5;i++) { read(fd, buff, 500*2); //DMA read call Print the buffer } memcpy to global buffer and send to host PC via USB /********************/ For i = 0; I will get the data from FPGA correctly, from i=1 onwards, data will be missed not entire 500words but in chunks of 16/32 words As I have also registered the callback, I am getting completion interrupt for the everytime! /*********Configurations and driver code*************/ #define FIFO 0x06000000; unsigned short *psr = (unsigned short *)FIFO; unsigned short *pdt = NULL; unsigned short *pdtPhy = NULL; acnt = 2; (16bit) bcnt = 500; ccnt = 1; Device_read(...) { pdt = (uint16_t*) kmalloc(500*2, GFP_KERNEL); pdtPhy = virt_to_phys(pdt); // initialise DMA if (davinci_request_dma(0, "DMATEST", davinci_edma_cb, NULL, &ch, &tcc, EVENTQ_0)) { return -1; } // set DMA parameters davinci_set_dma_dest_params(ch, pdtPhy, INCR, 0); davinci_set_dma_src_params(ch, psr, INCR, 0); davinci_set_dma_src_index(ch, 0, 0); // args: srcbidx srccidx davinci_set_dma_dest_index(ch, acnt, 0); // args: destbidx, destcidx davinci_set_dma_transfer_params(ch, acnt, bcnt, ccnt, 0, ABSYNC); // args: acnt, bcnt, ccnt, bcntrld, sync_mode // start DMA transfer davinci_start_dma(ch); copy_to_user(from Local buffer to User buffer); davinci_request_dma(ch); } /********************/ Do you think I have missed any configurations or is there a know problem with the driver? Note: Also tried to move the Request Dma Channel to OPEN method and Free Dma Channel to CLOSE method. Still no luck! Thanks and Regards, Nitin Joshi ________________________________ http://www.mindtree.com/email/disclaimer.html
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