2008-09-05 22:04:19     PPI and DMA problem

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2008-09-05 22:04:19     PPI and DMA problem

Matthew Wang (CHINA)

Message: 61719   


I am writing an av camera driver, there are an av camera sensor, TVP5150AM1 decoder and BF537 on my board


I make PPI and DMA enabled, it should generate an interrupt request, and DMA_IRQ_STATUS should be set, however it didn't work!!!


so when I writing a camera driver , HOW should I do to make PPI receive a frame data, and generate an interrupt , then DMA transfer the captured data from PPI to SDRAM


here is my register value:



REG: 03h register ---TVP5150AM1 Miscellaneous Control Register

VALUE: 0x09





   * PMAP[3:0]: PPI

   * CTYPE: Peripheral DMA


cd->ppiDev.dma_peripheral_map = 0x0;





   * FLOW[2:0]: autobuffer mode

   * NDSIZE[3:0]: Required if in stop or autobuffer mode

   * DI_EN: allow completion of work unit to generate a data interrupt

   * DI_SEL: interrupt after completing each row(inner loop)

   * SYNC: continuous transition

   * DMA2D: two-dimensional

   * WDSIZE[1:0]: 8-bit transfers

   * WNR: DAM is a memory write(destination) operation

   * DMAEN: disable DMA channel


cd->ppiDev.dma_config = 0x1096;



dmaBuffer = kmalloc( ( cd->videoV4l1.videoCap.maxwidth * cd->videoV4l1.videoCap.maxheight*4 ),

      GFP_KERNEL );  

cd->ppiDev.dma_start_addr = dmaBuffer;

cd->ppiDev.dma_x_count = 352;

cd->ppiDev.dma_x_modify = 2;

cd->ppiDev.dma_y_count = 288;

cd->ppiDev.dma_y_modify = 2;





   * PGTE: enable PPI D13, PPI D14, PPI D15

   * PGRE: enable PPI D10, PPI D11, PPI D12

   * PGSE: enable PPI D8, PPI D9

   * PFFE: enable PPI frame sync 3


cd->ppiDev.port_mux = PGTE_PPI | PGRE_PPI | PGSE_PPI | PFFE_PPI; //0x0100

cd->ppiDev.portF_fer = VALUE_PPI_CLK | VALUE_PPI_FS1 | VALUE_PPI_FS2 | VALUE_PPI_FS3; //0x8380

cd->ppiDev.portG_fer = VALUE_PPI_D0TOD15; //0xFF





   * POLS: PPI_FS1 and PPI_FS2 are treated as rising edge

   * POLC: PPI samples data on rising edge and drives data on falling edge of PPI_CLK

   * DLEN[2:0]: 8 bits

   * SKIP_EN: in ITU-R 656 and GP input modes, skipping disabled

   * PACK_EN: (packing mode) disabled

   * FLD_SEL: (active field select) in ITU-R 656 modes, when XFR_TYPE = 00, fields 1 and 2

   * PORT_CFG[1:0]: not used

   * XFR_TYPE[1:0]: in input mode, ITU-R 656, active field only

   * PORT_DIR: PPI in receive mode(input)

   * PORT_EN: PPI disabled


//cd->ppiDev->ppi_control = FLD_SEL | DLEN_8; //0x0040

cd->ppiDev.ppi_control = 0x00C0;

cd->ppiDev.ppi_frame = 288;

cd->ppiDev.ppi_count = 351;






2008-09-05 22:21:30     Re: PPI and DMA problem

Mike Frysinger (UNITED STATES)

Message: 61720   


there are a bunch of camera drivers that use PPI and DMA already in the distribution which you can review ... there is also some documentation on the V4L interface in the documentation wiki




2008-09-06 04:21:26     Re: PPI and DMA problem

yaqin yu (AFGHANISTAN)

Message: 61745   


hello!Mike Frysinger.

I use the same hardware with Matthew Wang.I configured the ppi and dma,but I can't get the capture data.I think maybe I understand the dma wrong.I config the dma and ppi with interrupt after one frame completed .when begint to capture, open the dam and ppi, it will transmit the data to buffer pointed by the dma_start_addr,which is configured in  dma_start_addr register.After a frame is transmited,a interrupt occure.In the interrupt routine,

diable the ppi and dma,then it can't capture. then I read the data in the buffer ,but it is null. Am I right? Thanks!




2008-09-07 11:32:37     Re: PPI and DMA problem

renjith kumar (INDIA)

Message: 61758   


hi all,


I find, this is a common problem that all the people struggle with initilly at starting phase of their project.


if someone could suggest the Best PPI-DMA configuration that gives the fastest throoughput in PPI ports,


it would be a great helping hand for All of us.


Please suggest if any alternative for DMA-PPI combination.


Is this the Only method to achieve this ???


Thanks and








2008-09-07 15:24:57     Re: PPI and DMA problem

Mike Frysinger (UNITED STATES)

Message: 61762   


there is no magical setting combination that will work best in all hardware/software configurations


we provide example drivers that work for cameras and framebuffers (lcds/etc...) which you can consult